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Community resilience to coastal disasters

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Community resilience to coastal disasters

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Community Resilience to Coastal Disasters

Lesley Ewing, P.E.

Submitted in partial fulfillment of the requirements for the degree
Doctor of Philosophy

The Sonny Astani School of Civil and Environmental Engineering
Graduate School
University of Southern California

August 2014

Page ii
Table of Contents

Abstract 1
Chapter One: The Importance of Coastal Communities 3
1.0 Introduction 3
1.1.Coastal Areas as Population and Economic Centers 3
1.2.Coastal Areas and Locations for Coastal Disasters 5
1.3 Disasters and the Importance of Community Resilience 9
Chapter Two: Coastal Communities 13
2.0. Introduction 13
2.1. Importance of Resilience at the Community Level 13
2.2 Infrastructure and its Effects on Community Resilience 14
2.3 Community Infrastructure – Critical Elements 16
2.4 Special Characteristics of Coastal Communities and Options for
Increased Resilience 27
Chapter Three: Coastal Hazards, Risks and Vulnerabilities 32
3.0 Introduction 32
3.1 Hazards, Risks, Vulnerability and Disasters: Definition of Terms 32
3.2 Coastal Hazards 33
3.3 Effect of Climate Change and Sea Level Rise on Coastal Hazards 39
3.4 Risk and Vulnerability 44
3.5 Engineering Studies in Support of Community Risk and Vulnerability 44
3.6 Risk and Vulnerability Assessments for Community-Scale Resilience 52
Chapter Four: Disasters – Lessons Learned for Resilience 55
4.0 Introduction 55
4.1 Coastal Disasters 55
4.2 Investigations of Recent Coastal Disasters 56
4.3 Lessons for Coastal Protection and Resilience from Prior Disasters 61
Chapter Five: Community Resilience and Coastal Protection 66
5.0 Introduction 66
5.1 Definitions of Resilience 66
5.2 Resilient Cities and Communities 68
5.3 Climate Change, Adaptation, and Resilience 76
5.4 Managing for Resilience in Coastal Communities 77
5.5 Elements of Community Resilience 80
Chapter Six: Index for Evaluating Resilient Coastal Communities 90
6.0 Introduction 90
6.1 Determining Community Resilience from Protection Measures 90
6.2 Coastal Community Hazard Protection Index 98
6.3 CCHPR Index Application to Ocean Beach, San Francisco, CA 101
Conclusions 110
Appendix A: Tables for Coastal Protection Options 114
References 168

Page iii
List of Figures

Figure 2-1 Population of Orleans Parish before and after Hurricane Katrina
1960 – 2012 16
Figure 2-2 Port of New Orleans Cargo Activity before and after Hurricane
Katrina 16
Figure 2-3 Electrical Power Interdependencies 20
Figure 2-4 Water Supply Interdependencies 20
Figure 2-5 Wastewater Treatment Interdependencies 21
Figure 2-6 Trash and Debris Removal Interdependencies 21
Figure 2-7 Transportation Interdependencies 22
Figure 2-8 Communication Interdependencies 22
Figure 2-9 Emergency Services Interdependencies 23
Figure 2-10 Fuel Supply Interdependencies 23
Figure 3-1 Coastal bluff retreat, Solana Beach, CA, October 2004 38
Figure 3-2 Post-Glacial Sea Level Rise 40
Figure 3-3 Trends in Global Sea level Rise during the Industrial Era,
1870 to 2010 41
Figure 3-4 Global Sea Level Rise Change, 1993 to 2013 42
Figure 3-5 Various 2100 Global and Regional Sea Level Rise Projections 42
Figure 3-6 Trends between Water Levels and Coastal Consequences 43
Figure 3-7 Remains of tsunami forest in Rikuzen Takata, Japan, May 2011 49
Figure 4-1 Remains of Geotube Dune Protection installed at Galveston, TX 58
Figure 4-2 Scour Damage at Sea Isle Beach, Galveston, TX 59
Figure 4-3 Paloa, American Samoa. Damage from 29 September 2009
Samoan Tsunami 60
Figure 4-4 Seawall Failure at Koizuma Beach, Japan 64
Figure 5-1 Community Resilience and Functional Capacity 71
Figure 5-2 Generating Capacity in American Samoa following the 2009
Tsunami 72
Figure 5-3 PJM’s Electrical Service following Hurricane Sandy 73
Figure 5-4 Port of Kobe Container Traffic 74
Figure 5-5 Port of Kobe World Ranking in Cargo Traffic 75
Figure 5-6 Hypothetical Events to 100 Years 84
Figure 5-7 Hypothetical Events to 1,000 Years 84
Figure 5-8 New Orleans, Louisiana 86
Figure 6-1 Temporal Distribution of Four Disaster Phases - Various
Disaster Events 96
Figure 6-2 Ocean Beach, San Francisco (2003) looking south 102
Page iv
List of Tables

Table 1-1 US Population, Land Area and GDP 4
Table 1-2 Global Coastal Populations and GDP 4
Table 1-3 American Society of Civil Engineers Infrastructure Report
Cards 7
Table 2-1 Critical Urban and National Infrastructure and Resource
Elements 17
Table 2-2 Functions of Critical Infrastructure/Community Systems
during and after Disasters 24 - 25
Table 2-3 Current and Future Location Constraints on Community
Infrastructure 29
Table 3-1 Distinguishing Characteristics of Major Coastal Hazards 35 - 36
Table 6-1 Direct and Secondary Community Benefits from Coastal
Protection 95
Table 6-2 Coastal Community Hazard Protection Resilience Index
(CCHPR Index) 104 - 105
Table 6-3 CCHPR Index – Elements for Ocean Beach, San Francisco,
CA 106 - 107
Table 6-4 CCHPR Index – Application to Ocean Beach, San Francisco,
CA 108 - 109
Table 6-5 Normalized Values for Shore Protection from Ocean Beach,
San Francisco, CA 109
Table A-1 Coastal Protection Options – Technical Details 116 - 132
Table A-2 Coastal Protection Options – Effectiveness, Costs and Failure
Modes 133 – 150
Table A-3 Coastal Protection Options – Disaster Protection Values 151 – 159
Table A-4 Coastal Protection Options – Values During Recovery 160 – 163
Table A-5 Coastal Protection Options – Values During On-going
Activities 164 - 167

Page v
ACKNOWLEDGEMENTS

My coastal career began with a mid-life awakening to the challenges that exist at the water’s
edge. Despite the many years that millions of people have lived next to the coast, there remain
many questions about the futures of our coastal communities. I have been fortunate in having a
career that I enjoy, that allows me to delve regularly into some of these questions and that
regularly offers new challenges. Over time, I heard more and more groups discussing coastal
resilience and I realized that this was a topic into which I wanted to delve at more detail and with
more focus that I could bring to it without some life changes. Thanks to the encouragement and
support of many friends and work colleagues, I gathered the courage and fortitude to start and
finish the Ph.D program that supported this research on resilience.

Many people helped with this research. I was very fortunate that my supervisor, Susan Hansch,
would allow me fit classes and field investigations into a flexible work schedule. After news of a
coastal disaster, her first question would be ‘when do you leave?’, rather than, ‘do you have to
leave work again?’. I am grateful to my other colleagues for the patience during those times
when I had to postpone responding to work requests, and to the many people who filled-in when
I was not accessible.

The Coasts, Oceans, Ports and Rivers Institute (COPRI) and American Society of Civil
Engineers (ASCE) has long recognized that engineers need to go into the field after disasters to
capture perishable data and learn about the real-world performance of engineered structures. I
was very fortunate to receive support from COPRI, ASCE and the Japan Society of Civil
Engineers to participate in field investigations following the 2008 Hurricane Ike, the 2009
Samoan earthquake and tsunami and the 2011 Tohoku earthquake and tsunami. Their support for
these field investigations provided broad access to disaster areas that was critically important to
understanding details of the disaster and targeting elements of resilience.

Orville Magoon, Billy Edge, Bob Dean, Chris Jones, Jennifer Irish, Margaret Davidson, and
many other colleagues have provided data and gratefully served as sounding boards for some of
my more quirky ideas. Louise Wallendorf postponed planning the next Solutions Conference till
I could finish this dissertation. Phyllis Grifman opened her home to me for the past 6 years,
giving new meaning to ‘my home is your home’. Friends kindly allowed my to drop by for
dinner when I could not face another package of frozen food, gave me space when I needed it,
and reminded me that I occasional needed to sit back had have a beer or glass of wine and
remember that there is more to life than resilience.

Finally, I am very fortunate to committee members who provided academic inspiration, valuable
input and on-going encouragement. Costas Synolakis and Ron Flick have been colleagues for
many years, and I greatly appreciate their insights and guidance through much of my career, as
well as through the Ph.D. process. I am grateful for opportunity to work recently with Pat Lynett
and Daniel Mazmanian, and I look forward to working with all four of my committee members
in the future.

Page 1
Abstract

Coastal communities are some of the major economic centers in both the
US and the world; yet, the dynamics of the coast make these areas prone
to coastal hazards and disasters. Traditional responses to hazards have
been retreat, accommodation and resistance. The coast itself has provided
the first and more important protection for human communities, and for
early coastal communities, the shoreline was the primary protection. As
the shoreline moved, the community has responded by relocating,
expanding and retreating, thus providing for community survival when the
coastal features did not provide sufficient protection.

Resilience addresses both efforts to minimize the extent of damage that
results from a hazard event, and ways that the community responds to
damages and restores community functions. Resilience is joining the more
traditional approaches available to communities for reducing the
consequences of hazard events, which include erosion, inundation,
flooding and wave impacts.

Shore protection features, including natural protection, engineered
structures, and land use practices, provide community resilience during all
phases of a disaster -- the pre-event phase, the event phase, the recovery
phase, and the on-going activities phase. However, no method has been
developed to assess community resilience resulting from various
protection options. This research provides lessons learned about shore
protection, based upon investigations of several recent disasters. It also
provides a synthesis of many of the protection features in use, covering
how they function and the values they provide during all four phases of a
disaster (pre-disaster, disaster, recovery and ongoing activities), and the
development of a Coastal Community Hazard Protection Index (CCHPR
Index).

The CCHPR Index provides a measure of the resilience of a community’s
existing coastal protection and opportunities to compare the changes
community resilience brought on by different modifications or additions to
coastal protection systems. This research describes the development of this
index. It starts with an analysis of the key services of a community and the
interdependencies of these services. The key community services are
characterized within these four disaster phases as are aspects of coastal
hazard events. Coastal protection options are identified and evaluated for
their effects on resilience throughout the four phases of a disaster, and
these effects on resilience are used as inputs to the CCHPR Index.

The CCHRP Index provides information on how each protective feature
functions for disaster protection and the economic, environmental and
Page 2
social/cultural values that are provided. Vastly different features are
included in the CCHPR Index, providing broad options for communities.
The CCHPR Index provides a means to compare coastal protection
elements across several important community aspects that rarely have
intercomparable metrics – economical, environmental and social/cultural
aspects. The CCHPR Index does not depend upon scale, nor does it
require a detailed assessment of community vulnerability or evaluation of
the condition of existing shore protection. The assignment of high,
medium and low ratings to the economic, environmental and
social/cultural benefits (or costs) of each type of protection provides a
non-monetary comparison of options and a means to assess the current
protective options that are already in use by a community.

Page 3

Chapter One
The Importance of Coastal Communities

I need the sea because it teaches me
Pablo Neruda, The Sea

1.0 Introduction
Coastal areas have been centers of population growth and economic development for
centuries if not millennia. This section will discuss the importance of coastal settlements
throughout the globe and special risks to these areas from coastal hazards. It also covers
the impacts of disasters to coastal communities and the importance of resilience as an
opportunity for coastal communities.

1.1 Coastal Areas as Population and Economic Centers
For millennia people have been attracted to the coast, or the small area of the planet that
forms a triple juncture between air, land and water. Fishing was one of the earliest
occupations; boats were some of the earliest forms of transportation; and, shells were
some of the earliest forms of currency. Archeologists have found dugout canoes dated to
about 8,000 BC (Breunig 1996) and cowry shells were used in commerce starting about
1,200 BC in China and continuing to the middle of the 20
th
century in parts of Africa
(Lawler 2002; Davis and Banks 2002). Today, as in ancient times, coasts are areas of
abundant natural resources, major population centers and loci for economic development.

In the US in 2012, for example, almost 85% of the State Gross Domestic Product (State
GDP), came from coastal states (those with open ocean coasts and Great Lakes coasts),
and almost 50% came from coastal watershed counties (Colgan 2003). Almost 80% of
the US population lives in coastal states; yet, coastal states, including Alaska, comprise
only 57% of the land area (Table 1-1). The US, population and state GDP are
concentrated disproportionately in coastal states. And, if Alaska, with its large, but
sparsely populated land area is excluded from the analysis, the population and GDP
concentration discrepancy is even larger, since the non-Alaskan coastal states have less
than have the land area, yet almost 80% of all Americans live in these coastal states and
these states account for almost 84% of the national GDP.

Globally, as in the US, the coast is a center for substantial population growth. An
estimated 40% of the world’s population
1
now lives within 100 km of the coast; and
while coastal land lower than 10 meters makes up only 2.2% of the global land area,

1
sedac.ciesin.columbia.edu/es/papers/Coastal_Zone_Pop_Method.pdf
Page 4
currently 10% of the world’s population lives in the low-lying area (McGranahan et al.
2007). Thirteen of the 20 megacities (generally defined as those cities with more than 10
million residents) are coastal and several of the megalopolis corridors, such as Boston to
Washington DC on the US east coast, or Los Angeles to San Diego on the US west coast,
are along a continental edge.

Table 1-1. US Population, Land Area and GDP
2012 Population
(1000s)
Land Area
(1000s Sq. km)
GDP (10
9
$US)
2012
US, total 313,914 9,827 15,328
US, without Alaska 313,182 8,109 15,276
All Coastal States
(% US total)
248,365
(79.1%)
5,622
(57.2%)
12,875
(84%)
Coastal states, without Alaska
(% US, without Alaska)
247,633
(79.1%)
3,904
(48.1%)
12,823
(83.7%)
Source: US Department of Commerce, US Census Data 2012.

Globally, 600 million people live in coastal areas lower than 10-m MHW and 360 million
of these people live in urban areas (McGranahan et al. 2007). As shown in Table 2-1,
from 250 to 376 million people live below 5-m MHW and 100 to 150 million people live
below 1-m MHW (Anthoff et al. 2006; Rowley et al. 2007). The studies of population
were initiated to estimate the overall consequences of an accelerated rise in sea level;
however, since these the 1-m MHW generally indicates areas susceptible to flooding
from a moderate storm during high tide and the 5-m MHW generally indicates areas
susceptible to flooding from a severe storm so these studies are also an indication of the
populations that are exposed currently to coastal hazards.

The coasts are also centers for economic development. Estimates are that approximately
$944 trillion (US) of the global GDP (based on Market Exchange Rate) is situated
between mean high water (MHW) and 1-m MHW, and $1,802 trillion (US) GDP is
located lower than 5-m MHW (Anthoff et al. 2006). The values of development in low-
lying areas examine only the direct values of property and do not examine the indirect
values such as the businesses supported by coastal area wages, and the many in-land
businesses that are part of the supply-chain with links to the coast (Rose 2004).

Table 1-2. Global Coastal Populations and GDP
Population
(Million/%)
GDP MER
(Trillion $US/%)
Global, below 1m MHW 146M (2.2%) 944 (2.2%)
Global, below 5m MHW 268M (4.1%) 1,802 (4.2%)
Global, below 10m MHW 397M – 600M (6 - 9%) 2,570 (6%)
Source: Anthoff et al. 2006
Page 5
The coast has experienced population and economic growth for millennia as people have
established settlements and communities to take advantage of the many coastal resources
and the commerce and trade advantages provided by access to navigable water, and
despite the plethora of coastal hazards, this trend is expected to continue. From 2007 to
2050 global population is expected to grow from 6.7 billion to over 9 billion people.
Most of the population growth is expected to occur in urban areas – cities, megacities or
megalopolis corridors; some of this growth will most certainly occur in the coastal areas
that already are exposed to coastal hazards or that will be exposed to hazards in the
future.

1.2 Coastal Areas and Locations for Coastal Disasters
Coastal disasters are regular occurrences and their impacts can be massive. The 21
st

century has already experienced extreme coastal disasters around much of the globe –
tsunamis in the Indian Ocean, Samoa, Chile and northeast Japan, Hurricanes Katrina, Rita
and Ike in the US Gulf of Mexico, Cyclone Nargis in the Irrawaddy delta, Superstorm
Sandy along the eastern US seaboard and Typhoon Haiyan in the Philippines. These
events each resulted in a large number of fatalities, social impacts, environmental
destruction, and enormous financial losses including damage or destruction of buildings
and infrastructure, disruptions to businesses, and lost livelihoods. Almost 230,000 people
were killed or missing and presumed dead and about 1.7 million people were displaced
due to the 2004 Indian Ocean tsunami and the economic losses exceeded $14 billion US
(Guy Carpenter 2005). The 2011 Tohoku earthquake and tsunami caused over 15,500
casualties, and between $250 and 309 billion US in damages. The earthquake and
tsunami also led to rolling brownouts due to reduction the national electrical generation
by 8.8 gigawatts (3.3%), with the largest loss attributable to critical damage to Units 1, 2
and 3 of the Fukushima Daiichi Generating plant and eventual shutdown of the entire
plant (International Atomic Energy Agency 2011).

Hurricane Katrina caused an estimated 1,500 deaths and $81 billion US in damages
(Beven et al. 2008); cyclone Nargis was estimated to be responsible for almost 85,000
fatalities, 54,000 missing people, 2.4 million people impacted, and $4 billion US in either
asset damages or lost income (Union of Myanmar 2009). Myanmar’s policy of economic
isolation perhaps minimized the impacts from Cyclone Nargis to other regions, but most
of these events caused business disruptions that rippled through the global economy.
These disasters also had enormous, broad-scale social and ecological impacts; however,
none of the disaster damage estimates to date fully cover loss values for either social
disruption or ecological damage.

Coastal disasters and damages to the coast do not occur just during extreme events.
Hurricane Ike was only a Category 2 hurricane when it made landfall on the east Texas
coast, yet it ranked as the third most costly hurricanes in the US, followed Hurricanes
Katrina and Andrew (FEMA 2008a). In 2012, Hurricane Sandy demoted Hurricane Ike to
the 4
th
most costly storm, and it will be only a matter of time before all these ignominious
rankings are surpassed by other coastal storms. Current climate research predicts that
many coastal hazards will worsen in the future due to an increase in global temperature,
Page 6
rising sea level and possibly to an intensification of storms and hurricanes (Stern 2007;
Emmanuel 2005; FitzGerald et al. 2008; Resio and Irish 2008; Ruggiero 2008; Kumar et
al. 2008; Cayan et al. 2008). These factors, combined with population growth, damaging
storms, floods, droughts, heat waves, cold snaps, and erratic, changing weather patterns,
are stressing communities throughout the world.

Many communities, from villages to mega-cities, are facing these stressors with aging
and often poorly maintained infrastructure. This is especially true in the US where, since
1988, the American Society of Civil Engineers (ASCE) has provided general ratings of
the nation’s infrastructure. As seen in Table 1-3, overall grades have been either D or D+,
with a 2013 estimate of $3.6 trillion US needed to meet the national infrastructure needs,
remedy problems, and correct deficiencies. Coastal communities face all the same
infrastructure deterioration problems and stressors as inland communities, but also must
contend with concerns about permanent inundation of land,
2
ocean flooding, shoreline
erosion, wave impacts, hurricanes, and tsunamis. And, climate change and rising sea
level will exacerbate all of these coastal stressors in coming decades.

Hazards that strike individual communities have repercussions that extend far beyond the
disaster site. Due to expanded travel, immigration and global commerce, most human
communities have become interconnected and interdependent. Unlike early, self-
sufficient walled cities and isolated villages, modern cities are major population centers
relying upon resources and business markets around the globe. This is especially true for
coastal communities that are linked to both coastal and inland regions through commerce,
transportation, communication, utility services and, more and more often, through
familial and personal relationships. Due to the vast networks that exist between
communities, hazard losses are not limited to the damaged community and the
consequences do not end at the limit of the damaged zone or the community boundary.
Disasters can have indirect impacts and ripple effects to multiple communities around the
world. The immediate loss of life and property, social and environmental damages are of
obvious concern; but the other losses are the hours, days, weeks or years until the
community services are restored – until the utility systems are back on-line;
transportation systems are able to move people, goods and services; residents have shelter
and dependable access to food and water; dependable government and social services are
provided; businesses reopen; environmental services and quality of life are restored, and
daily routines are re-established.

Most coastal hazards and disasters are triggered by natural processes, and human actions
can either increase or decrease their impacts. Events such as tsunamis, storms, hurricanes
and cyclones become major disasters, if they cause a large number of fatalities or
extensive damage to the built environment. Development in coastal lands vulnerable to
hazards can intensify the consequences of a hazard event and escalate a damaging event
to the status of a disaster. Human activities can also alter the intensity or severity of these
events; for example, increased emissions of greenhouse gas have been linked to increased

2
Permanent inundation can be the result of rising sea level, land subsidence from glacial isostatic
adjustment, seismic and aseismic activity, fluid withdrawals, or some combination of rising water
and dropping land elevation.
Page 7
sea level and possibly to increased frequency and intensity of some storm activity;
removal of coastal dunes, mangroves and offshore reefs can increase exposure of coastal
areas to waves and storms; increased groundwater levels can reduce slope stability and
increase erosion of coastal bluffs; increased hardscape in watersheds and building in
floodplains can intensify flood events and make them flashier; diversion of surface water
can change flood patterns; and, reservoirs and flood control structures can change
sedimentation patterns and reduce coastal sediment supplies.

Table 1-3. American Society of Civil Engineers Infrastructure Report Cards
Infrastructure 1988 1998 2001 2005 2009 2013
Highways/Roads C+ D- D+ D D- D
Bridges C- C C C C+
Mass Transit C- C C- D+ D D
Rail C- C- C+
Aviation B- C- D D+ D D
Schools F D- D D D
Water Resources B
Water Supply/Drinking B- D D D- D- D
Wastewater C D+ D D- D- D
Dams D D D D D
Solid Waste C- C- C+ C+ C+ B-
Hazardous Waste D D- D+ D D D
Navigable Waterways D+ D- D- D-
Ports C
Levees D- D-
Energy D+ D D+ D+
Parks and Recreation C- C- C-
Security I
Average N.A. D D+ D D D+
Total Infrastructure Needs
(Trillions of Dollars US)
$1.3 $1.3 $1.6 $2.2 $3.6
Grades: A = Exceptional; B = Good; C = Mediocre; D = Poor; F = Inadequate; I = Incomplete.
Each category was evaluated on the basis of the condition and performance, capacity
versus need, and funding versus need.
Source: ASCE Infrastructure Report Cards.

Human activities can also reduce the severity of natural events or their consequences by
such activities as diverting floodwaters away from developed areas; building vegetated
dunes, wetlands, offshore reefs, wind breaks, and other ecosystems that can buffer wave
or storm forces; erecting seawalls, revetments, levees and bulkheads to resist wave
forces; or, developing and enforcing building and seismic codes for construction.
However, human efforts have not reached the point of controlling the fundamental
geophysical, oceanic and atmospheric conditions that generate hazardous events,
although human induced climate change may result in modifications to some
fundamental atmospheric conditions. Even so, tsunamis, storm events, erosion, flooding,
Page 8
hurricanes, cyclones and other coastal hazards will shape much of the coastal
environment for the foreseeable future.

Few coastal disasters can be considered entirely unexpected; many disasters can be
anticipated based on precedent and scientific understanding of their causes. Even
extreme events such as the Indian Ocean, Chile and Tohoku tsunamis, Hurricanes
Katrina, Rita, and Sandy, and Cyclone Nargis, could have been anticipated.
Seismologists, geologists and geophysicists recognized the destructive power of the
Sunda subduction zone in the Indian Ocean and its tsunami-genic potential. Records of
high water levels from previous tsunamis were evident throughout the coastal region that
was damaged by the Tohoku tsunami. And, engineers with the New Orleans District of
the US Army Corps of Engineers had been pointing out the vulnerabilities of the New
Orleans levee system for years prior to Hurricane Katrina.

Cyclone Nargis caused extensive damage in Myanmar, and one reason given for the level
of damage was a poor knowledge of storm surge (Union of Myanmar 2009). This cyclone
was unusual in that it traveled toward the east; nevertheless the Bay of Bengal has
frequent cyclone development, and there was early warning about Cyclone Nargis. The
Bay of Bengal experiences about 10 cyclones each year and Cyclone Mala,
3
another Very
Severe Cyclonic Storm,
4
had occurred just two years before, also making landfall in
Myanmar. And, over the last 60 years, a dozen cyclones had caused extensive damage to
coastal areas of Myanmar – on average, one devastating cyclone every five years. With
such patterns of cyclone activity, poor knowledge of storm surge should not have been an
issue when Cyclone Nargis made landfall. Almost every “unexpected” coastal disaster
has a precursor, precedent or pattern to anticipate the event; the only unexpected things
are the timing, magnitude and intensity.

Each disaster can provide valuable lessons in how to redevelop near the coast in ways
that will lessen the consequences of the next event. Technical groups such as national
engineering associations, the United Nations, and national Research Councils have
undertaken costly and time-consuming field investigations to help document many of the
recent disasters to insure that the lessons from recent events are captured and
documented. One of the recurring lessons from coastal disasters is that communities
cannot rebuild as they were before the disaster. In the words of Albert Einstein, ;Doing
the same thing again and again and expecting different results is the definition of
insanity.’ The field investigations and examinations of disasters are efforts to guide
redevelopment in ways that will improve response to and recovering from future events.

3
During Cyclone Mala, winds exceeded 240 km/hr (150 mph) and storm surge exceeded 4.5m
(14.8 ft).
4
The classification of Very Severe Cyclonic Storm is equivalent to a Category 4 storm on the
Saffir-Simpson scale.
Page 9
1.3 Disasters and the Importance of Community Resilience
Following the Indian Ocean tsunami, the US Indian Ocean Tsunami Warning System
Program, with support from the US Agency for International Development (USAID)
prepared A Guide to Evaluating Coastal Community Resilience to Tsunamis and Other
Coastal Hazards. This guide outlined various community resilience outcomes for
governance, resource management, land use, risk knowledge, warning, evacuation and
disaster recovery. It recommended general resilience benchmarks for policy and planning
capacity, physical and natural system capacity, social and cultural capacity, and technical
and financial capacity (U.S. Indian Ocean Tsunami Warning System Program 2007). A
key aspect of this work was that it established the importance of resilience for the routine
character and fabric of community and not just something that is important during and
after a disaster.

Hurricane Katrina also spurred communities to rethink disaster preparedness. Following
the devastation of New Orleans and other Gulf of Mexico communities by Hurricane
Katrina, the Hurricane Katrina External Review Panel (ERP) and the Interagency
Performance Evaluation Task Force (IPET) made recommendations for better
understanding and communication of risks, and for a dynamic risk-based approach to
hurricane and surge protection. Prior to Hurricane Katrina, New Orleans had a collection
of protective elements with different purposes, designs and design conditions; different
ownership, levels of construction oversight, and attention to maintenance; and different
responses to the hurricane forcing. In post-Katrina evaluations, these protective elements
were described both as a system that did not perform as a system, and as a collection of
levees and pumps that were designed and developed in a piece-meal fashion (IPET 2009,
pg. 130). Some of the destruction in 2006 resulted from the failure or collapse of a small
section of protection that then led to progressively larger damage.

Even though the protection in New Orleans was not constructed as a system, it responded
to the hurricane as a system and the weak elements of protection that collapsed put added
stress on other sections, leading to cascading collapses. One main focus of the post-
Katrina reconstruction was to replace the prior protection elements with a more systems-
wide approach to protection of the entire community. Their recommendations for
resilience included the upgrading the main levees and floodwalls, designing protection
systems for both redundancy and to maintain functionality when overtopped (i.e. avoid
catastrophic failure), developing clear lines of responsibility, and improving interagency
coordination and update engineering design procedures (ASCE Hurricane Katrina 1009;
IPET 2009).

The Tohoku-Oki tsunami that hit the coast of Japan in 2011 provides other lessons in
coastal resilience. The island nation of Japan is very vulnerable to tsunamis and records
extending back over a thousand years document damage from these events. The word
tsunami developed as the combination of two Japanese words, tsu for harbor and nami for
wave. And, the Japanese governments had made tsunami protection a national, regional
and local priority by providing extensive public education programs about the warning
signs of a tsunami; developing warning sirens and evacuation routes; and providing
Page 10
engineering expertise and funding for the construction of tsunami protection, in the form
of breakwaters, walls, flood gates, dikes and even tsunami forests.

The Japanese engineering for tsunami protection remains some of the most advanced in
the world; yet, on March 11, 2011, a subduction zone seismic event generated tsunamis
that overwhelmed many of the engineered defenses. An obvious observation from the
tsunami was that the 9- and 10-meter high tsunami barriers were not high enough to
protect the inland areas and many of the structures were overtopped. Engineering teams
undertook more detailed field investigations, finding that many of the tsunami barriers
and other shoreline protection collapsed, in part because they had not been designed for
overtopping (ASCE-COPRI-PARI 2013). The design efforts had not fully accounted for
the worst case or “what if” situations.

The reports from the Indian Ocean tsunami, Hurricane Katrina and the Tohoku-Oki
tsunami are but three of the disaster reports that highlight the big issues for coastal
communities:
1. coastal communities will continue to be vulnerable to coastal hazards,
2. the magnitude of the hazard can exceed the best engineering efforts, and
3. coastal communities need to be better prepared for both the hazards and the
resulting disruptions.

Resistance to coastal forces is often an important aspect of community survival; however,
resistance will not protect from every event. Furthermore, regular rebuilding for
resistance alone will be both a drain on the community and on resources. Resilience
needs to become a component of coastal protection for communities. Resilience can
mean relocating structures and infrastructure out of vulnerable areas; building structures
to be more resistant to anticipated wind, wave and storm forces; improving the
effectiveness of natural or naturalized protection; building protective dikes, walls and
other barriers; providing better monitoring and warning to allow more people to leave the
most high-risk areas and evacuate to areas of greater safety; and, providing education on
hazards and hazard warnings so people in high-risk areas understand the risks and
available risk reduction options.

Resilience is the ability of a community or system to maintain functionality during most
events and then rapidly restore function after an extreme event. In this research report,
community function is mainly addressed through infrastructure and essential services.
This research focuses on resilience of coastal protection efforts. This resilience derives
from a combination of good engineering, good land use planning, redundancy of critical
systems, enhancement of natural systems that mute or buffer coastal forces, and some
elements to resist coastal forces. It is important for every coastal community to both
survive hazards and recover in ways that will help the communities be better able to cope
with future events.

Resilience is important at all scales and for all types of communities. Many types of
community settlements exist along the coast. Quite often, small, subsistence fishing and
farming villages have changed into large urban areas; but smaller coastal villages and
Page 11
rural communities still exist throughout the world. The existing coastal hazard
infrastructure, as well as the available resilience resources and options will often be quite
different for these community types. For example, a number of small Alaskan
communities are threatened by erosion and flooding, such that entire settlements might be
lost within the next 5 to 10 years (GAO 2009). Relocation, albeit difficult, has been
considered as a serious option for these villages. The island nation of Kiribati, with a
population of about 100,000 is also considering relocation due to the threat of rising sea
level.
5
But, the space and resources to relocate small villages or even small nations is
vastly different from what would be required for Los Angeles, Miami or New York City.

This research focuses primarily on the options available to the larger and more developed
coastal communities that have already made substantial investments in protective
infrastructure and urban development. While the discussions focus on the engineering
and physical impacts of the various protective options, rather than on the governance and
implementation, the US system of land ownership and property rights is included
occasionally in aspects of the analysis. Yet, while this research on resilience does not
address the issues facing those communities that are transitioning from village to urban
center concerning, some benefits, pitfalls and long-term consequences of various
protection options may prove to communities before they embark upon various types of
protection efforts.

The research focus on resilience of coastal communities is due both to the social,
commercial and environmental values of these areas and due to the dynamic character of
coastal hazards. Consequences from coastal disasters can have ripple effects that extend
far beyond the immediate coastal region. However, coastal communities are not just at
risk from coastal hazards. Coastal communities are vulnerable to all other the hazards of
the area, in addition to the coastal hazards. The Philippines is a good example of this,
where, in 2013, typhoon Haiyan caused massive damage in the central Philippines,
arriving less than one month after 270,000 people had been left homeless by a M 7.1
earthquake. Such events challenge recovery efforts and thwart routine expectations
regarding relief efforts and recovery times.

The National Research Council (NRC) recently undertook an examination of disaster
resilience at a national scale, entitled Disaster Resilience, A National Imperative (NRC
2012). Key recommendations from the study are the need for communities to understand
their risks so they can make “appropriate investments to prepare and plan for hazards and
risks” (NRC 2012, pg. 4). The NRC report also noted the lack of guidance on how to
value various community assets.

This research report addresses several of the information needs that have been raised in
the NRC report, providing information on coastal hazards and risks, the roles of coastal
protection in community resilience to coastal disasters, and developing a system for
valuing the components of coastal protection. Specifically, this research examines the
coastal processes that lead up to coastal disasters and that pose the greatest challenge to

5
http://www.theglobalmail.org/feature/kiribati-a-nation-going-under/590/, last visited 20Jan2014.
Page 12
community resilience, the community elements or components that are important for
recovery during and after a disaster, and what is meant by resilience to coastal disasters in
terms of functionality and time to recover following a disaster, and the resilience values
from various protection options. Field investigations and case studies form a major core
of this research and the basis for fitting coastal protection elements into the larger
framework of community resilience to coastal disasters.

The resultant community resilience model examines coastal hazards, areas vulnerable to
coastal hazards, the community components that are at risk from coastal hazards and
community scale options to reduce potential consequences of coastal events. The
objective is to provide a method for evaluating existing community resilience and the
efficacy of various options to increase community resilience to likely coastal disasters.
Researchers familiar with the characteristics and forces of other, non-coastal hazards
should be able to easily expand this resilience evaluation to non-coastal hazards.

Page 13

Chapter Two
Coastal Communities

Till my soul is full of longing for the secrets of the sea,
And the heart of the great ocean sends a thrilling pulse through me.
Henry Wadsworth Longfellow – Secret of the Sea

2.0. Introduction
Some of the most basic aspects of communities are the provision of lifelines and
infrastructure, such as transportation, power, water, wastewater treatment, debris
disposal, and communication systems. This report examines many of these basic
community services and the interconnections or interdependencies of these services.
Several of these basic services take on different roles and importance during times of
disaster. While these services and their roles during disasters tend to be similar for all
communities, due to the marine orientation of coastal communities, several important
services are concentrated along the coast. This chapter will examine the
interdependencies of various services, their roles during disasters, and the special risks to
these services in coastal communities due to their frequent proximity to the coast. This
understanding of community services is important since the ability of a community to
provide basic services during and after a coastal disaster will, in many cases, determine
the community’s resilience to disaster and ability to recover.

2.1. Importance of Resilience at the Community Level
All communities
6
provide residents and visitors various services – governance, defense,
financing and access to financial markets, opportunities for education, shelter,
employment, commerce, health care, social services, cultural enrichment, open space and
recreation areas, to name a few. Some of the most basic aspects of communities are the
provision of lifelines and infrastructure, such as transportation, power, water, wastewater
treatment, debris disposal, and communication systems. And, the ability of a community
to provide these basic services during and after a disaster will, in many cases, determine
the community’s resilience to disaster and ability to recover.

Communities such as cities and urban centers have the size, existing organizational and
financial structure, and the collective elements to be foci for resilience, bridging the gap
between household and state or national resilience. And, in the US, cities have authority
for land use planning, enabling them to direct future growth in ways that might foster
better disaster response and recovery. Researchers and planners are already focusing on

6
This report will use the definition of community from National Academy of Sciences 2013
Disaster Resilience: A National Imperative, which uses community “in a very broad sense,
encompassing the full range of potential communities – including local neighborhoods, family
units, cities, counties, regions and other entities”.
Page 14
cities for opportunities to address climate change and increase sustainability (Biello
2012). Much of the guidance and many of the recommendations for coastal development
planning (Pawlukiewicz et al. 2007), preparedness for tsunamis and other hazards, and
adaptation for climate change and sea level rise are geared toward community-scale
efforts.

The 2005 Hyogo Framework for Action expressly identifies communities in the primary
outcome, “the substantial reduction of disaster losses, in lives and the social, economic
and environmental assets of communities and counties” and calls out community level
efforts for “building resilience to hazards” ((UN, ISDR 2005, pgs. 3 and 4). In a 2013
workshop on climate resilience, (CERES et al. 2013), a group of insurance industry
leaders and city stakeholders found that community level actions are important for overall
resilience and that resilience on an asset-by-asset or structure-by-structure approach
leaves gaps. The “community level is where risks accumulate and where the benefits of
action accrue.” (CERES et al. 2013, p. 12)

The general concept of hazards, disasters, vulnerability and risk includes both an event
that serves as a stressor, disruption, or threat, and the people, ecosystems, structures or
activities that may be stressed, disrupted or threatened by the event. In a discussion of
community resilience, it is important to understand which elements of the community are
of concern. Studies of what is meant by a resilient human settlement note that
communities and cities are complex systems and most elements of these systems are
important for recovery. There are some aspects of recovery that are common across most
communities, such as restoration of utilities, ability to travel to and around the affected
areas, and access to communication and information. There are also aspects of recovery
that are location specific. For example, in New Orleans, artists and musicians were some
of the first groups to return to the city and help re-establish the sense of place and culture
that had been so much a part of the city prior to Katrina. And, following the attack on the
World Trade Center in New York City, restoration of the financial network was a priority
both for the symbolic purpose of rebuilding what had been attacked and because it was
important to the identity of the community.

2.2 Infrastructure and its Effects on Community Resilience
This report examines communities and community resilience in terms of infrastructure
that can be thought of as a community’s lifelines. There are several reasons for this focus
on infrastructure. First, infrastructure is a keystone vulnerability as described by
McManus et al. (2008), where keystone vulnerabilities are those components of the
community system that, if damaged, have the potential to cause major damages
throughout the community. In addition, infrastructure/lifelines are often quasi-public and
“larger than individual” aspects of a community. Community elements, such as housing
and businesses, while integral to a community’s day-to-day existence as well as to
disaster recovery, are primarily held in private ownership as individual elements of the
community. Finally, infrastructure recovery influences both social and economic
recovery. Failure of infrastructure and key lifeline elements can prolong the recovery
time and cause longer disruptions to businesses and the local economy (Kurtulus 2011).
Page 15

Drawing again from New Orleans, where large portions of the city are at or below sea
level, the flood protection elements such as pumps and levees, are key lifelines for the
community. After Hurricane Katrina destroyed most elements of the flood control
system, temporary flood protection efforts were installed as part of the immediate
recovery efforts. However, it took seven years to replace the haphazard array of levees,
pumps and drainage canals with a comprehensive, $14.5 billion US flood protection
system that included surge barriers, floodgates, pumps and a drainage system
7
. Isolated
parts of the city were able to recovery fairly quickly. For example, the Port of New
Orleans was able to restore its facilities rather rapidly; however, the port recovery was
hampered because the longshoremen and other port workers were focused on family
concerns and on finding replacement housing, and the timing for their returning to work
affected the return of the port to full service (Curtis 2007). The population of New
Orleans has had a much longer recovery.

Just before Hurricane Katrina, the population of Orleans Parish was estimated to be
454,865 (estimate for July 1, 2005, just two months before the August 29
th
landfall), and
the year after Katrina, the population dropped by half, to about 223,000
8
. By 2012, when
the city’s flood control projects were completed, offering far greater protection than
before Katrina, the population of Orleans Parish had increased to only 369,250 -- or about
80% of the pre-Katrina level.
9
As shown in Figures 2-1 and 2-2, the full recovery of a
community can be a long-term effort. In the case of New Orleans, where the trends for
port activity and population growth were both declining prior to Hurricane Katrina, full
recovery may result in a new normal, rather than a return to the prior condition.

7
The comprehensive system includes the Lake Borgne Surge Barrier and the Seabrook
Floodgate, providing protection along the eastern and northern portions of New Orleans along
with pumps and drainage systems.

8
The pre-Katrina population estimate was for July 1, 2005, just two months before the August
29
th
landfall (US Census, Population estimates by parish). Population for 2006, and the year after
Katrina, based on an estimate by Paul Rigamor and reported by B. Bohrer. 2007 New Orleans
Population Up, Washington Post, August 8, 2007, http://www.washingtonpost.com/wp-
dyn/content/article/2007/08/08/AR2007080801499.html (last visited 14Jan2014).

9
US Department of Commerce, US Census Bureau. State & County QuickFacts. 2012.
http://quickfacts.census.gov/qfd/states/22/22071.html, last visited 14Jan2014.
Page 16
Figure 2-1. Population of Orleans Parish before and after Hurricane Katrina 1960 – 2012.
Source: US Department of Commerce, US Census Bureau

Figure 2-2. Port of New Orleans Cargo Activity before and after Hurricane Katrina
Source: American Association of Port Authorities, US Port Rankings by Cargo Tonnage

2.3 Community Infrastructure – Critical Elements
Infrastructure or more specifically critical infrastructure and lifelines are fundamental to
community restoration. Community assets can be classified many different ways and
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1950 1960 1970 1980 1990 2000 2010 2020
Population
Year
New Orleans Population
(1960 - 2012)
0
20,000
40,000
60,000
80,000
100,000
1994 1996 1998 2000 2002 2004 2006 2008 2010 2012
Total Cargo
(Thousands of Short Tons)
Year
Port of New Orleans Cargo Activity
(1996 - 2011)
Page 17
Table 2-1 shows several of these classifications and as can be seen, there is no single,
agreed-upon list of critical community infrastructure or services.

Table 2-1. Critical Urban and National Infrastructure and Resource Elements
Ascher –
Anatomy of a City
NRC –
Critical
Infrastructure
ASCE –
America’s Infrastructure
DHS –
Critical Infrastructure
& Key Resources
Sector
Systems that move
people
Water Water & Environment Agriculture and food
Systems that move
goods
Waste Water Dams Defense Industrial
Base
Power Systems Power Drinking Water Energy
Communication
Systems
Transportation Hazardous Waste Healthcare and Public
Health
Cleaning Systems Telecommunications Levees National Monuments
and Icons
Solid Waste Banking and Finance
Wastewater Water (drinking water
and wastewater
systems)
Transportation Chemical
Aviation Commercial Facilities
Bridges Critical Manufacturing
Inland Waterways Dams
Ports Emergency Services
Rail Nuclear Reactors,
Materials, and Waste
Roads Information
Technology
Transit Communications
Public Facilities Postal and Shipping
Public Parks &
Recreation
Transportation
Systems
Schools Government Facilities
Energy

In a 2009 National Research Council (NRC 2009) report on infrastructure, the National
Research Council (NRC) committee defined critical infrastructure elements as those,
“without which buildings, emergency response systems, dams and other infrastructure
cannot operate as intended” NRC 2009, pg vii). The NAS study recognized that every
community has numerous lifelines, but the critical infrastructure elements could be
narrowed down to five general elements: water, wastewater, power, transportation, and
telecommunications. The NAS study also recognized that there are inter-dependencies
within infrastructure, such that loss of one element can disable or disrupt other
infrastructure elements.

In Anatomy of a City,

Ascher (2005) divides cities into systems that move people, such as
streets, subways, bridges and tunnels; systems that move goods, such as rail and maritime
Page 18
freight, air cargo, and markets; power systems, such as electricity, natural gas and steam;
communications systems such as telephone, mail and the airwaves; and systems that keep
the community clean, such as water, sewage and garbage. Unlike the NAS classification,
the Ascher classification is intended to identify the essential day-to-day elements of a
community. Nevertheless, the Ascher classification is in general agreement with the NAS
identification, except Ascher combines water and waste into the category of systems that
keep the community clean whereas the NAS study separates them into two categories.
Ascher separated the movement of people and movement of goods into separate
categories whereas the NAS puts these together in the general category of transportation.

The American Society of Civil Engineers (ASCE) provides a third classification of
infrastructure, looking at the built environment. Since 1988, ASCE has prepared
infrastructure report cards that assess the physical elements of the nation’s infrastructure
and their functional condition. The initial report evaluated 12 elements, and the most
recent report from 2013 has an evaluation of 16 different categories of infrastructure that
fall within main categories of water, environment, transportation, public facilities, and
energy.
10
The Department of Homeland Security, which is concerned with both natural
and human-caused disasters, has a separate list of 18 asset categories that are of concern
for disaster management.

Table 2-1 shows these different infrastructure classifications. Since infrastructure is a
broad class of community assets, there is no single definitive list and as seen from the
ASCE Infrastructure Report Cards, the list can evolve and grow with time. The 1988
Report Card covered only eight asset classes, and by 2013, the Report Card covered 17
asset classes. The 2005 Report Card covered only added security as a new, but not
completely evaluated asset class. However, by 2009, this asset class had been dropped
from the Report Card without finalizing any complete evaluation.

The lists or identifications of assets shown in Table 2-1 were prepared for specific agency
or society purposes, but they provide a range of facilities that make up the built
community. The DHS categories were prepared with a focus on national security, health
and welfare, addressing security from terrorist attacks, natural disasters and other
emergencies. The ASCE and NAS studies have been undertaken in recognition that many
of the US infrastructure lifeline systems will need major rebuilding or replacement efforts
in the coming years. ASCE has used this information to encourage the US Congress to
appropriate more funds for infrastructure maintenance and replacement. The NAS has
used their analysis to emphasize that this infrastructure renewal will provide an
opportunity to examine these systems, their service and function, interdependencies and
ways to leverage available resources for multiple purposes and for greater overall
resilience and sustainability.

One aspect of infrastructure is that, generally, it covers broadly-used public or public-
oriented elements of the built environment. Not all parts of a community are considered
critical – either as critical infrastructure or critical community elements. Housing and

10
American Society of Civil Engineers: http://www.infrastructurereportcard.org/grades/.
Page 19
shelter are not identified in any of the infrastructure lists, even though they are most
certainly part of a resilient community and are critical parts of community recovery.
While water is on each of the lists, food is only included in the DHS list, due to concerns
about disruptions to agriculture and the national food supply system. However,
communities rarely rely fully upon locally-sources food, and if the transportation system
is functioning, food can be delivered from areas outside the zone impacts by the disaster.
These lists do not include community functions, except for the physical aspects of these
functions, such as schools, parks or monuments and government facilities; nor do they
address any of the natural areas or open space areas that add to community quality.

Whatever listing of infrastructure elements is used, community infrastructure systems are
interconnected. The idea of connectivity is a basic tenet of ecosystem management and
environmental studies, but is also true for built, urban systems. For example, financial
systems rely upon communication systems for all by the most basis barter, cash or I-owe-
you (IOU) transactions. Recovery of a wastewater system is of little value if there is no
electricity for the plant NAS 2009). And, after most major disasters, homes and
businesses that survived the disaster cannot be occupied until utilities were restored.

Modern day infrastructure and lifeline systems are often interdependent, and loss of one
service can have ripple effects in other, potentially unrelated areas. For example,
following Superstorm Sandy, gas stations were unable to supply fuel because their pumps
needed electricity to operate. Awareness of these interdependencies can also help with
community resilience. Even if a water plant remains intact following a disaster, it may
not be able to provide safe drinking water, if there is no electrical supply to run the
pumps and filtration systems, or if the pipelines have cracked allowing polluted water to
combine with the treated water once it leaves the plant. Figures 2-3 through 2-10 show
the level of interdependencies between each of these infrastructure systems. The lines
between the service function on the inside of the ring and those on the outside indicate
the number and significance of the dependencies of the outer ring services on the inner
service. The thickness of the lines indicates the number of different dependencies and if
there are no lines, there are not identified dependencies. These linkages or dependencies
are between the services themselves and do include the services that the workers in each
facility might need or require. So, for example, a water supply system might need
electricity for the water pumps and this is identified as interdependency. Workers in the
water plant might also need electricity for their office functions; however this is not
included as interdependency since it is not specific to the water supply function directly.

Infrastructure and lifelines may provide different services under routine operating
conditions, during a disaster, and during disaster recovery. Just as it is important to
recognize the interdependencies of these services, so too is it important to understand
their importance for community resilience during and after a disaster. Table 2-2 covers
some of the major services of infrastructure and lifelines under day-to-day situations,
during a disaster and during recovery.

Page 20

Figure 2-3. Electrical Power Interdependencies. Many services depend upon electricity
for some aspects of the service. Water, wastewater and fuel supplies often use electrical
pumps, water and wastewater use electrical power for filtration. Trash and debris removal
could use electrical power for sorting lines. Transportation might use electrical power for
signals and traffic management, electric vehicles, subway systems, cold ironing ships, or
cranes. Some uses would be community-specific.

Figure 2-4. Water Supply Interdependencies. Water is in general demand for cleaning at
for all services. Water may also be used for cooling in power plants, communication
systems. It is also used for sanitation in emergency services, as well as for soil
compaction and dust suppression.
Page 21

Figure 2-5. Wastewater Interdependencies. Wastewater treatment is important to all
office systems; however, for the service components, it is important for waste removal
and human health concerns in emergency services.

Figure 2-6. Trash and Debris Interdependencies. Trash and debris removal is important
for maintaining overall access to facilities. It may be important for electrical plants that
run on bio-fuels or trash combustion. Trash and debris removal is also important for
removal of biomedical waste from emergency service facilities.

Page 22

Figure 2-7. Transportation Interdependencies. Transportation is important for access to
facilities and to transport fuels for power generation and fuel supplies. It is also important
for conveying water, wastewater, trash and debris to the necessary treatment centers.

Figure 2-8. Communication Interdependencies. Communication services are important
for reporting on service outages, tracking fuel or traffic flows, and coordination for
search and rescue.
Page 23

Figure 2-9. Emergency Services Interdependencies. Most service functions include
several job classifications that can be considered high risk or can expose employees to
special chemicals or to greater risks than are experienced by the general population. As a
result, all these services have a general dependency upon emergency services.

Figure 2-10. Fuel Supply Interdependencies. Similar to electrical power, most service
functions use some form of power for pumps, filtration, and mechanical sorting. If
electrical power is not available directly, facilities will rely upon back-up generators and
fuel supply will be critical. In addition, most vehicles and equipment will need a regular
source of fuel to keep running.
Page 24
Table 2-2. Functions of Critical Infrastructure/Community Systems during and after Disasters
Critical Facility Routine Functions Pre-disaster Functions
(In addition to routine
functions)
Disaster Function
(In addition to routine
functions)
Recovery Function
(In addition to routine functions)
Electrical Power Power plant start-up
Power plant operations
Administrative activities
Water treatment facilities
Pump water
Wastewater treatment
Wastewater lift stations
Pump wastewater
Traffic signals
Power for mass transit
Power pipelines
Pump fuel
Radio, TV, Internet
Telephone service
Hospital operations
Radio – Dispatching
Building Systems -- lighting,
HVAC, communications
Power for sirens and
early warning systems
Building evacuations
Shut-down of operations
or convert to stand-by
mode for mass transit,
elevators, traffic signals,
industrial operations, etc.
Close surge barriers,
locks, tsunami gates, etc.
Power for sirens and early
warning systems
Safe evacuation from
buildings
Media alerts (TV, radio,
internet, smart phones, etc.)
Safe shut-down of operations
or convert to stand-by mode
for mass transit, elevators,
traffic signals, industrial
operations, etc.
Power for emergency centers
Restart off-line power plants
Pump wastewater and flood water
away from low-lying areas
Power communication links –
phones, TV, & radio
Fuel distribution and delivery
Support and maintain emergency
services & safe hospital conditions

Water Drinking water
Fire suppression
Power for steam engines
Power for plant cooling
Cleaning
Landscaping irrigation
Industrial uses
Fire suppression Cleaning
Sanitation
Waste Water
Treatment
Remove and treat domestic
sewage and industrial effluent
Health and Safety
Storm water treatment
Contain waste and
minimize releases of
untreated waste, with
sufficient warning time
Contain waste and minimize
releases of untreated waste

Contain waste and minimize
releases of untreated waste
Prevent spread of contagious,
water-borne diseases
Trash & Debris
Removal
Remove and reduce trash
volumes; store in controlled
landfills
Minimize amount of
floating debris &
projectiles, with sufficient
warning time
Minimize amount of floating
debris & projectiles
Clear roads for emergency
access, search & rescue
Clear debris from critical facilities
to allow post-disaster operations
Page 25
Critical Facility Routine Functions Pre-disaster Functions
(In addition to routine
functions)
Disaster Function
(In addition to routine
functions)
Recovery Function
(In addition to routine functions)
Transportation Move people and goods
Remove trash and debris
Support evacuation Support evacuation, if safe
Pre-stage response and
recovery efforts
Search and rescue
Move supplies, fuel, generators,
drinking water, food, medicine
Transport people to hospitals and
shelters
Communications Support internal operations
for all utilities
911 calls
Medical dispatching
Information exchange
Early warning systems
911 calls and medical
dispatch
Early warning systems
911 calls and medical
dispatch
Early warning systems
911 calls and medical dispatch
Convey information about
shelters, programs to reunite
families
Multi-directional information
centers
Emergency
Services
Non-routine health care
Search and Rescue

Early warning systems Early warning alerts
Respond to 911 calls
Health care
Medical triage
Search and Rescue
911 Response
Communication center
Set up shelters, and programs to
reunite families
Fuel Supplies Power plant start-up &
operation
Water treatment facilities
Pump water
Wastewater treatment
Wastewater lift stations
Pump wastewater
Construction site power
Power for autos, trucks, mass
transit, ships, and planes
Power pipelines
Pump fuel
Power for sirens and
early warning systems
Safe shut-down of
operations or convert to
stand-by mode for mass
transit, elevators, traffic
signals, industrial
operations, etc.
Close surge barriers,
locks, tsunami gates, etc.
Power for sirens and early
warning systems
Safe evacuation from
buildings
Safe shut-down of operations
or convert to stand-by mode
for mass transit, elevators,
traffic signals, industrial
operations, etc.
Power for emergency centers
Power plant start-up
Power for back-up generators
Pump water
Wastewater treatment
Wastewater lift stations
Pump wastewater
Power for emergency vehicles,
trucks, mass transit, ships, and
planes
Power pipelines
Pump fuel
Radio and dispatching
Page 26

Figures 2-3 through 2-10 and Table 2-2 illustrate how the various infrastructure systems
and lifelines interact and help highlight the likely consequences to other services, when
one infrastructure element fails or suffers diminished capacity. Figures 2.3 through 2-10
all use the same structure; the main infrastructure system is in the middle and lines
connect this system to those systems which depend upon this service, with the thickness
of the line indicating the number of services that depend upon the main system. For
example, Figure 2-3 shows the services that depend upon electrical power. Since
electrical power systems use electrical power for start-up and other power regulation,
there is a connection between electrical power to electrical power. Transportation relies
upon electrical power for many aspects of the system, such as traffic signals, electric cars
and trains, and cold ironing of vessels while at port. Fuel supplies rely upon electrical
power for fuel pumps. Since transportation relies upon electrical power for more system
aspects than does fuel supply, the line between electrical power and transportation is
heavier than the line between electrical power and fuel supply.

The information in these figures is rather generic, and the specifics will be different from
one community to another. When the services are examined with the functions of each
system under normal conditions as well as within the phases of pre-disaster, disaster,
response, and recovery, the resulting information will help a community prioritize
infrastructure resilience. For example, if all the emergency response systems rely upon
fuel supplies, then protection of the supply chain for fuel would be a major aspect for
disaster response. As shown in Table 2-2, other facilities or functions may rise in
importance during other phases of pre-disaster, disaster, response, and recovery.

Disaster response and recovery has changed over time, as settlements have become more
permanent and as people’s expectations and technological options have changed
11
.
Extensive relocation or community abandonment following a disaster has not been
undertaken in recent times. Relocation is possible for individuals or families, but
complete resettlement of cities is increasingly difficult due to the social, economic and
emotional ties that have been established with the area, the magnitude of the relocation
and the lack of land that can support a new urban center. So, disaster response and
recovery focuses on reestablishment of the community functions in the same general
area. Thus, if a community experiences extensive damage, the typical response will be to
rebuild and return to the same general area.

One perspective on disaster recovery is that disasters provide opportunities to rebuild
communities to be better and more resilient than they were prior to the disaster. Aging
infrastructure can be replaced with newer systems; and vulnerable assets can be relocated

11
The examination of transient versus permanent settlements has been discussed in many
contexts. Several interesting examinations of ‘mobility versus sedentary living’ are provided in
Brian Fagan’s 2013 book, The Attacking Ocean (New York, Bloomsbury Press). For example,
the Poverty Point settlement along the Mississippi River had been settled possibly as early as
2000 BCE, with evidence of permanent settlement by about 1650 B.C.E. Yet, changes in river
flooding patterns and intensities at around 1000 B.C.E. made continued occupation impossibly
difficult and the community was abandon.
Page 27
or built to have greater resistance. The concept of community improvement is lost if
community resilience is evaluated only as the ability of a community to return to
functionality, especially if the community infrastructure was only marginally adequate
before the disaster. The ASCE Report Card effort (Table 1-2) has found that many of
America’s infrastructure systems are inadequate or only marginally adequate at meeting
current system demands. Although level of service of infrastructure is not normally
included in an examination of asset vulnerability, it can be an important part of asset
vulnerability, the resources available for disaster response and recovery, and improved
community resilience.

Communities do not need to wait for a disaster to examine the appropriateness of a
business-as-usual approach. The need for contingency planning was one of the lessons
from the Tohoku tsunami, and it is an useful element for overall resilience planning.
Utilities and critical infrastructure planners should not wait for a disaster to plan their
response to a major event. Anticipating the consequences of a disaster can be motivation
to make improvements or even undertake relocation prior to a possible disaster. If actions
are not completed prior to the event, the efforts in contingency planning can provide a
foundation for post-disaster recovery actions that can enhance long-term resilience
(Ewing et al. 2010).

Community elements like parks, open space, recreational areas and intact ecosystems
have both environmental and social values that, while often less tangible than constructed
infrastructure, can be equally important to community resilience. Green infrastructure can
help control runoff, dampen flooding and improve water quality. Open space areas
provide opportunities for healthful exercise and social interactions. Ecosystems provide
nesting, spawning, and breeding habitats for species that are critical to the food chains.
Just as with the quality of service of constructed infrastructure, an evaluation of the
presence and quality of these areas will be important for asset vulnerability and
community resilience.

2.4 Special Characteristics of Coastal Communities and Options for
Increased Resilience
Coastal communities tend to have a special set of characteristics that can influence
approaches for community resilience. Most important is that coastal community
development is shaped by proximity to the coast. As coastal communities grow, the water
boundary precludes expansion in a radial pattern expanding in all directions from the
central downtown core. The development in coastal communities occurs only on the
land-side region, forming elongated development corridors along the coast and extensive
inland growth.

Transportation and commerce often rely heavily upon travel along the coast and
commercial links between land and water. The historic use of ocean waters for power
plant cooling and wastewater disposal has led to a concentration of industrial
development close to the shoreline. Beaches and wetlands function as urban parks,
providing much of the open space and recreation areas for visitors and residents.
Page 28
Development patterns in coastal communities have led to the concentration of a large
amount of important community infrastructure on or in close proximity to the coast, often
in areas highly susceptible to coastal hazards. Of the eight systems examined in Figures
2-3 through 2-10 and Table 2-2, electrical power, waste water, and fuel supplies often are
concentrated along the coast. Transportation corridors sometimes are concentrated along
the coast, and with increased development of desalination water, water systems will also
rely upon proximity to the coast to function. Unfortunately, these services that
concentrate in the high-hazard coastal areas also tend to be the services with the greatest
number of interdependencies. So, if one of these services is taken off-line by a coastal
disaster, there could be ripple effects through other services that depend upon this
service.

Most coastal communities are already developed. The land use patterns, infrastructure
systems and coastal features already establish a pattern of vulnerability or resilience.
Some land use activities are so tied to the coast that they are often identified as being
coastal dependent. Ports are an obvious example; fisheries are another. A number of
facilities co-locate with these activities to be close to the key assets. Fish processing
plants and shipyards congregate near fishing harbors. Transportation hubs with rail and
road linkages develop near ports; and if fuel ships through the port, then oil and gas
facilities will also locate at or near the port.

Proximity to water is often a key factor in land use patterns. For example, water and
waste water systems have historically relied upon gravity to move water into or away
from a community. Wastewater does not have to be conveyed to the coast; but traditional
practice has been to discharge storm water and waste water into an open body of water,
be it the ocean, river lake or sea. The industrialized version of this practice now uses
treatment plants to clean the waste before sending it into a body of water through
discharge pipes and outfall structures. Green infrastructure technology is attempting to
incorporate as many natural clean up and treatment options as possible to lessen the
nutrient concentrations and mechanical controls that are part of the industrial style of
waste treatment. Green infrastructure can also lessen the need for storm water disposal.
Water infrastructure, and systems for waste water disposal are and will remain important
community functions; however, the existing linkage to the coast that has been established
through existing technology and land use patterns may not be important to this
functioning in the future.

A key aspect in community resilience is recognizing what assets need to be in areas that
are vulnerable to coastal disasters, such as ports or fishing harbors; what assets are in
areas that are vulnerable to coastal disasters due to prior land use practices or
development patterns, such as warehouses and airport facilities; and, what assets may
undergo changes that will enable them to move from the coast such as, power plants or
wastewater treatment plants. The importance of location for these assets should be part of
a community’s decisions on ways to make each function more resilient. If some assets
can be relocated with no diminishment in the overall service, then through resilience
planning, a community can plan to move these services to less vulnerable areas as they
need to be replaced. If technical changes or system modifications are needed,
Page 29
communities might assume protection for a period of time until retirement or replacement
of the assets that are in vulnerable areas.

An important perspective for community resilience is to focus on the function of key
infrastructure assets instead of focusing on individual elements of the system. Options for
providing transportation or wastewater treatment are far more expansive than are options
to maintain a specific highway, rail line, airport, electrical facility or water treatment
plant. As noted in Table 2-3, many of the current systems have options that can greatly
reduce place-specific constraints. Facility relocation or replacement may not be an easy
option; yet, it does represent an option for long-term resilience and cannot be overlooked.

Table 2-3. Current and Future Location Constraints on Community Infrastructure
Infrastructure/Lifeline Current location constraints Future location constraints
Electrical Power Proximity to water for cooling Renewable energy sources
will reduce need for water
access
Water Higher elevation, if possible to
use gravity flow
No change
Waste Water Treatment Low elevation, if possible, to
use gravity flow
Green infrastructure will
reduce need for centralized
waste water treatment
Trash & Debris Removal N.A. Recycling may reduce volume
of trash; no changes to
locational constraints.
Transportation Often coastal to link
communities
Greater use of mass transit
may reduce rate of road
construction, no changes to
locational constraints
Communications N.A. More reliance on internet
communications, no change in
locational constraints
Emergency Services Along coast, in densely
developed areas
No change
Fuel Supplies Near ports, airports and
transportation facilities
Fuel mix may change with
increased use of renewable
fuels; could reduce need for
centralized fuel delivery
systems

Proximity to water is both a strength and weakness for coastal communities. Over the
years, most coastal communities have sought to take advantage of access to sheltered
water areas. Yet, while water access is important, protection from water-related hazards
such as flooding, storms, and tsunamis, has also been of concern. This can result in
internal tensions between easy access to the coast and all the benefits that come with such
proximity, and avoidance of hazard areas and all the dangers and damages that can occur.

One of the main responses to this tension between access to the coastal amenities and
protection from coastal hazards has been to construct protective features. These structures
offer some level of protection for community assets, allowing them to remain in high
Page 30
hazard areas. Coastal communities have built seawalls, revetments, breakwaters, surge
barriers, levees, dikes, and even tsunami barriers to provide protection in locations that
otherwise might be too hazardous for high-investment development. These structures,
along with natural features, such as beaches, reefs, and wetlands, form the initial level of
community defense against coastal hazards.

Yet, like other infrastructure, the constructed protective works are often aged and poorly
maintained; their protective capacity often diminishes over time while the hazards they
will face are the same, or possibly worse. And, very often, construction and development
has either displaced or greatly diminished the protective capacity of the natural shoreline
features. The net result for many coastal communities is that their protection from and
resilience to coastal disasters relies upon a combination of natural features with
diminishing protective capacity and built structures that are often were not sufficient to
address current and future hazard levels.

Physical protection, including both engineered structures and natural features, is an
important element of community resilience. Following the 1900 destruction of Galveston
by a hurricane, the central downtown area closest to the coast was raised and the
Galveston seawall was installed (Hansen 2007). Similarly, the City of New Orleans has
used elevation and levees for physical protection since the early settlement efforts. In
workshops to identify actions for climate resilience cities (CERES et al 2013), physical
resilience was a key priority for risk management, with a focus on risk-based protection,
such as a specific recurrent interval event, such as a 1-in-50 year or a 1-in-100 year event.

Appreciation is growing for the coastal protection that is available from natural systems
and intact ecosystems, like marshes, beaches, and reefs. One protection option that was
discussed frequently following Superstorm Sandy was the restoration of oyster reefs to
dampen the energy of the storm waves. The NYS 2100 Commission even included
recommendations for living shoreline efforts and planted oyster beds for protection of
infrastructure close to the coast (NYS Commission 2013). The beds would not reduce the
overall water elevation, but could dissipate some of the wave energy and reduce the flood
velocity due to the increased bed friction and bed elevation.

The elements of a coastal community that provide physical resilience – the built
structures, the managed features and the natural features – collectively protect the
functions of the community, yet they themselves are often integral to one or more
community functions. Natural systems such as wetlands or mangroves can provide an
important water quality function; offshore reefs can provide economic, environmental
and recreational functions. Natural or managed features like beaches are linked through
nutrient supplies and habitat to nearshore ecosystems, and they provide a social and
recreational function. Some engineered structures, like the Galveston and O’Shaughnessy
seawalls in Galveston and San Francisco, support pedestrian and vehicle transportation,
support recreation and provide, for now, a transition between the developed urban area
and the adjacent beach. Few of the physical resilience features are simply protection from
an identified event or coastal hazard. Most of the physical resilience elements provide
multiple functions that have day-to-day utility and community value. In most space-
Page 31
constrained coastal communities, it would be difficult, if not impossible to build or
engineer each community benefit provided by these multi-functional physical resilience
elements.

Of course, each community has different expectations from the coast, for the social,
environmental and economic values that the coast provides and the significance of the
various elements that provide physical resilience. Changes to various community or
coastal attributes will change the values of those attributes. Resilience needs to be
evaluated within a similar multi-value effort – so that, ideally, coastal changes will
increase overall community quality. Actions to protect individual elements of the
community need to examine the effects of this protection on other community assets and
include an appreciation for the values that the community places on each asset. If a
beach or wetland is an important social and environmental asset, then actions to protect
houses or roads that are to the detriment of the beach or wetland will increase resilience
of socio-economic assets, but reduce the resilience of the natural features. Protection
steps can change the balance of quality of these community values at whatever level.

As will be discussed in more detail in later sections, community resilience is an ever-
present characteristic of coastal communities, not just a 1-in-50 or 1-in-100 year event.
Critical facilities, those components of a community that will influence the functional
losses and recovery, will change with time. If the roles of these facilities are recognized
within the context of community resilience, then the long-term changes can be
undertaken in ways that will improve overall community resilience. Such options can
include relocating non-coastal dependent facilities away from high hazard areas,
decentralizing facilities and incorporating “green” elements into the system that have
built in resilience.

Elements that provide resilience, such as seawalls or beaches, will be an on-going part of
the community, and they can enhance or detract from community resilience during a
variety of situations. Community protection, just like the identified community services,
will provide different functions and community values during and after a disaster than
during routine situations. The temporal phases of resilience, within the context of a
disaster, are the disaster warning period, the disaster itself, post-disaster response, and
then recovery and on-going actions until the occurrence of the next event. The pre-
disaster warning period may be very short or non-existent and for those situations, the
phases compress to the three, disaster, response and recovery. If there is a long time
between disasters, the recovery period can become something akin to ‘business-as-usual’,
which can be used for rebuilding and preparing for the next event. And, as will also be
discussed later, the protection features of a community may have different functions and
be of different utility for each of these temporal phases of resilience.

Page 32

Chapter Three
Coastal Hazards,
Risks, and Vulnerabilities

The surf releases all its tremendous energy as it breaks against the shore,
sometimes delivering blows of almost incredible violence.
Rachel Carson, The Sea Around Us

3.0 Introduction
A fundamental understanding of coastal hazards is important for consideration of coastal
disasters and options for resilience. This Chapter covers some of the basics of coastal
hazards, definition of terms, explanations of the basic sources of coastal hazards, their
characteristics immediately prior to landfall, during the event and immediately after the
event. This Chapter also covers the mechanisms for damage from coastal hazards, the
consequences of rising sea level and some of the important basin-scale, landscape-scale
and community-scale modeling that is important for characterizing hazard risk and
vulnerability. This Chapter draws upon existing studies and research to provide the
foundation for the discussion of coastal disasters in Chapter Four.

3.1 Hazards, Risks, Vulnerability and Disasters: Definition of Terms
The ever-changing water levels and shifting shoreline conditions are part of the coast’s
fascination and sources of many of its hazards. Gently breaking waves can be hypnotic;
large storm waves can be hazardous. The shift from calm conditions to storms of
incredible violence is part of the continuum of coastal processes. Both gentle summer
waves and storm waves are generated through the interactions of wind blowing across the
surface of the water. Dynamic changes to the coast are also part of regular coastal
processes. Gentle waves help build up beach area through small, almost imperceptible
movements of sand from the nearshore to the beach; then, in a few hours, storm waves
can remove months-worth or years-worth of beach accretion or erode meters deep into
coastal bluffs and dunes. Areas that are untouched by waves during gentle conditions can
rapidly be flooded by meters of water, during wave attack, storm surge, or flooding.
These dynamic changes in shoreline position and water levels are part of the changes that
have formed our coastlines over time.
12
The resilience of coastal communities depends
upon a good understanding of these hazards, their characteristics, and their consequences.

Coastal hazards arise when these processes and changes to the coast threaten people or
the things they value (Cutter 2001). Some coastal hazards, like tsunamis, have special
triggering mechanisms, such as large earthquakes, submarine landslides, volcanic

12
While many coastal changes have resulted from natural conditions, there are many situations
where human activities have exacerbated these conditions.
Page 33
eruptions or meteor strikes. Others, like tropical cyclones or hurricanes, are the extreme
versions of routine events. Other hazards are the convergence of several events, such as
high surge or storm waves combined with high tides or a series of storms that occur with
such frequency that there is no time for recovery between events so that the cumulative
efforts will far exceed the expected consequences of each individual event. For example,
in 2014, numerous small to moderate storms occurred in southwest England; none were
unusually large, but they occurred without sufficient time for the waters to recede before
the next storm arrived, resulting in wide-scale flooding throughout the region.

Concerns about coastal hazards and disasters have become linked closely to risk and
vulnerability. Hazards, risks, disasters, and vulnerabilities are each slightly different
concerns, but the terms are occasionally used interchangeably (Cutter 2001). Different
researchers and disciplines each ascribe various connotations to these terms. The
semantic distinctions in their use are not the focus of this paper, but some general
definitions are appropriate.

A hazard, in the broadest sense, is a threat to people and the things valued by people.
Hazards represent potential sources of damage or danger. Hazards arise from the
interaction between social, technological, and natural systems (Cutter 2001, pg. 2). In a
coastal context, hazardous events include storms, hurricanes, tsunamis, waves, erosion,
and floods.

Risk has multiple definitions. In some situations, risk is the probability of an event
occurring, or the likelihood of a hazard happening. In this context, risk is a component of
a hazard and it emphasizes the estimation and quantification of probability in order to
determine appropriate levels of safety (Cutter 2001, pg. 3). In disaster and risk
management, risk is often similar to the consequences resulting from a hazardous event.
In this context, risk is based on the possibility of damage or a damaging event and the
associated losses.

Vulnerability is the potential for loss and it has been variously defined as the potential
exposure to a hazard, the capacity to suffer harm, and the sensitivity of different types of
development or social groups to certain hazards (Cutter 2001, pgs. 13 - 14). Exposure
refers to the physical location of assets relative to the hazard; sensitivity considers the
degree to which a system is affected by or changed by a hazard (IPCC 2012).

A disaster is a specific, identifiable event that results in widespread losses to people,
infrastructure, or the environment (Cutter 2001, pg. 3).

3.2 Coastal Hazards The major coastal hazards are inundation, flooding, wave
impacts, and erosion resulting from storms, El Niño storms, hurricanes, tsunamis and
other high wave events. Sea level rise, while not directly a hazard, will exacerbate these
hazard conditions. Coastal communities are exposed to many other hazards as well. For
example, around the Pacific Ocean, many of the coastal areas are also seismically active
areas that experience earthquakes, landslides and soil liquefaction. Coastal areas may also
Page 34
be prone to non-coastal hazards such as droughts or wild fires. These non-coastal hazards
may be of similar or greater significance than coastal hazards in terms of exposure,
sensitivity, and consequences and are not to be ignored in overall community hazard
planning, but are not themselves coastal hazards. Other hazards, such as vertical land
movement (even co-seismic uplift or subsidence) are likely to interact directly with
coastal hazards and are part of a coastal disaster, insofar as they alter exposure, sensitivity
or consequences of coastal hazards.

Coastal hazards in this study are limited to those physical hazards that have the potential
to threaten life or property at a community scale. Coastal hazards such as shark attacks,
box jellies, or rip currents can pose significant threats, but not at a community scale. And,
while oil and sewage spills can pose a community-wide threat, they are not linked
primarily to physical coastal processes, except in their transport following release.

Extreme coastal events are, almost by definition (Ewing and Synolakis 2012), outside the
normal parameters; but to initially gauge or understand an extreme event, there must be
some awareness of what is “normal”. Hazardous events or disasters would have been
viewed as randomly destructive occurrences until there was some awareness that there
were patterns or causal explanations for the events. Once events had some explanation
other than being random or “acts of god”, the concepts of risk and vulnerability can
develop.

Certain coastal events such as hurricanes, tsunamis, storm waves, El Niño storms,
flooding and erosion are now regularly considered to be hazardous due to their potential
to put coastal communities at risk or become a disaster. The events share similar damage
mechanisms through which damage can occur during these events include high water
level, strong currents and eddies, impact forces when water or waves hit a structure,
erosion and scour. The consequences can include injuries, fatalities, property losses
ranging from damage to complete destruction, environmental damage, reconfiguration of
the shoreline, interruptions of routine community activities, and short- or long-term
disruptions of economic activity.

While coastal hazards share some of the same damage mechanisms, there are some major
differences between, for example, an El Niño storm and a tropical cyclone or a tsunami.
Table 3-1 provides some of the distinguishing characteristics of each hazard and the
possible influences from climate change. The table does not address the recovery phase
of the disaster since recovery is often very similar across events, including search and
rescue, debris clean up, field investigations to establish wave run-up and flooding zones,
and rebuilding. These post-event recoveries are also the times when communities have
the opportunity to consider site-specific and community-specific opportunities for
improved resilience, which is discussed in later sections.

The characteristics of each coastal hazard will influence options that communities can
consider for resilience. The short time period associated with pre-event warnings limits
the safety or protection activities that can be undertaken immediately before the event.
The event characteristics indicate the safety and protection options that could minimize
Page 35
consequences. The post-event characteristics indicate the options and timing for response
and recovery, and influences due to climate change indicate suitability of using historic
trends and prior disasters to approximate future events.

Table 3-1. Distinguishing Characteristics of Major Coastal Hazard Events
Event Type Pre-Event Event Post-Event
Condition
Influences from
Climate Change
Tsunami Triggered by
disturbance of the
ocean – seismic
event, submarine
slide, volcanic
eruption, meteor
strike.
Short warning time
for near-field
events, no natural
warning for far-
field events
Evacuation often
possible even as
waves make
landfall.
Independent of
weather conditions
Long-period
waves
Rapid flooding
Fast currents
Waves or bores of
water in 20 to 30
minute cycles.
Scour
Rapid drawdown
Duration of
damaging waves
can be 12 to 18
hours
Duration of all
waves can be 2 –
3 days.
Occurrence during
high tide can
accentuate
impacts.
Standing water
only on low land,
in depressions, or
trapped by
barriers.
Large inland
deposits of sand
and debris
Broad zone of
destruction
Plant damage
from saltwater
Salts leach into
soil
Clear delineation
of unaffected
areas
Damage results
from wave
impacts, flooding,
currents and
scour.
Aftershocks can
limit safe access
to damaged areas
Areas inland of
run-up zone have
no damage.
None have been
identified.
Hurricane or
Tropical
Cyclone
Preceded by low-
pressure system,
heavy winds and
storm surge
Weather services
now track these
storms across the
ocean, providing a
1 to 2 day of
warning time.
Evacuation
immediately prior
to landfall
hindered by high
winds.

Surge, waves, rain
and wind all linked
together
Slow rising surge
with short period
waves
Fast currents and
scour
Duration of
flooding can be
hours or days
Duration of water
retreat can be 6 -
8 hours
Occurrence during
high tide can be
significantly
worsen impacts.
Large areas of
standing water,
often freshwater
Large inland
deposits of sand
and debris
Large volumes of
sand moved
offshore
Broad zone of
destruction, no
clear boundary for
undamaged areas
Damage results
from combination
of wind, rain, and
waves.
Possibility for
shift toward
fewer tropical
cyclones, but
with an increase
in storm intensity
and rainfall.
Page 36
Event Type Pre-Event Event Post-Event
Condition
Influences from
Climate Change
El Niño
Storms
Warm water build
up along equator
and eastern
Pacific
Storms preceded
by low pressure
system, with 1 to 2
days warning.
Elevated water
levels, storm
waves and heavy
precipitation are
often linked
together
Swell is often
linked with
antecedent
storms, can
worsen storm
waves
Rapid beach
erosion
Large waves,
Scour
Duration of storm
can be 1 to 2 days
Combination of
peak storm and
high tide can
significantly
worsen conditions.
Large volumes of
sand moved
offshore (erosion)
Moderate to
broad zone of
storm and wave
destruction, no
clear boundary for
undamaged areas
Damage results
from combination
of waves, high
water and rain.
Inland flooding
due to storm drain
back-ups and
inability of inland
waters to drain.
Possible
increase in
frequency of
extreme events.
Erosion
Episode
Beach, dune, and
bluff erosion often
driven by storm
events and large
waves
Bluff erosion can
be preceded by
cracks in upper
bluff or faulting/
landslide
conditions.
Rapid drop in
beach elevation as
sand is carried
offshore.
Retreat of bluff
bringing bluff
sediments to the
beach or
nearshore.
Initial beach
recovery within
days to weeks,
often not to pre-
event conditions.
Longer term
beach and dune
recovery can be a
season to several
years. Long-term
erosion of beach
and dune is
possible
Bluff retreat
irreversible within
foreseeable time
periods.
Increased inland
migration of
beach face due
to sea level rise
and greater
inundation.
Increased inland
retreat of dunes
and bluffs due to
adjustment in
beach position
and increased
frequency and
power of wave
attack due to
higher water
levels from sea
level rise.
NOTE: Duration estimated based on general characteristics of recent hurricane events and review
of water level plots showing differences between predicted tide levels and observed water levels.
Sources: Developed from professional judgment and information from Knutson et al. 2010;
Geophysical Fluid Dynamics Laboratory 2013; and Cai et al. 2014.

Erosion. Beach erosion can be the seasonal changes in the beach or the long-term
changes in beach shoreline position. Seasonal changes are often strongly associated with
the wave climate, where the higher energy storm waves and “winter” waves pull sand off
the beach and the milder, “summer” waves bring sand back onto the beach. Surveys of
week to week beach change for southern California beaches have shown that sand is lost
from the upper beach profile far more quickly that it is returned (Yates et al. 2011). So,
Page 37
once a beach shoreline has narrowed, it may remain narrow for weeks or months before
recovery. Long-term beach erosion, resulting from wave action, storms, and changes in
sediment supplies, can result in a chronic narrowing or landward migration of the
shoreline. In some situations, this may be accompanied by the inland relocation of the
back shore, or, if the back shore position is fixed, it will result in an overall narrowing of
the upper beach zone. Sea level rise will increase beach erosion, or the landward retreat
of the beach.

The direct threats from both seasonal and long-term beach erosion are that inland
structures may be undermined; there can be a loss of foundation support; and the stability
of the buildings, roadways, pipelines, or other development supported by the beach will
be at-risk. The loss of beach width will also lessen buffering and dissipation of wave
energy and flood waters in front of inland development. So, an indirect impact from
beach erosion can be increased damage to inland development from wave attack and
flooding.

Dune erosion also results from wave energy. In a beach-dune system there is often an
exchange of sand between the beach and dunes. When there is excess beach sand, wind
will carry it into the dunes resulting in dune growth. But, as waves erode the beach area,
the back dune system can serve as a sand storage system, providing additional sand to the
beach and nearshore areas during storm events. The cycle of sand exchange between the
beach and dune, like seasonal beach change, is rapid in the dune erosion phase and
slower in the dune recharge phase. The transfer of sand from the dunes to the beach can
occur in a few hours during a storm, but the rebuilding of the dune may take several
years, if there is enough sediment in the littoral cell. If new supplies of sediment are not
available in the area, the beach-dune system may become a one-way conveyance of sand,
where the dunes rarely, if ever, experience any accretion. Climate change will likely
increase dune erosion due to greater exposure of beaches and dunes to wave energy.

Dune erosion, like beach erosion, can cause inland structures to be undermined or lose
foundational support; and, the stability of buildings, roadways, pipelines or other
development on or in the dunes will be at-risk. The loss of dune width will also lessen the
buffering and dissipation of wave energy, causing indirect impacts similar to those
associated with beach erosion. And, a migrating dune system can move inland, sand
blasting and covering inland development or overrunning roads, filling drainage areas
and reducing their utility and safety.

Coastal bluff erosion, as shown in Figure 3-1, can result from wave attack as well as
geologic faulting, landslides, and groundwater soil saturation. Coastal bluff erosion is not
considered to be reversible. Bluffs can accrete from seismic activity over thousands of
years, but bluffs will not rebuild within human-scale time periods. Erosion can occur as a
gradual, chronic loss of bluff material, or it can be rapid and episodic. Most bluffs
experience both chronic and episodic erosion, although the episodic events are the ones
most people notice and remember. A bluff-backed beach has some similarities to a beach-
dune system. As the beach narrows, the back bluff will experience greater wave attack
and bluff will retreat. Bluff retreat will in turn add sediment to the littoral zone and help
Page 38
widen the beach. And increased bluff erosion can be another indirect impact from beach
erosion, sea level rise, or both.

The direct threats from bluff erosion are that inland structures can be undermined or lose
foundational support, putting buildings, roadways, pipelines or other development at risk
of collapse. Development on the bluff face, like stairways or drainage or outfall pipes can
be at risk, as well as any people using the beach during episodic bluff erosion.

Figure 3-1. Coastal bluff retreat, Solana Beach, CA, October 2004
Photo Credit: Jay Kitti, SEC.

Inundation and Flooding. Flick et al. (2012) have defined inundation as “the process of
a dry area being permanently drowned or submerged” and it can result from long-term
erosion, land subsidence or sea-level rise. In contrast, flooding occurs when “dry areas
become wet temporarily – either periodically or episodically” (Flick et al. 2012, pg.
365.). These definitions are not used uniformly. For example, in the tsunami literature,
inundation is used interchangeably with flooding and the tsunami inundation zone is the
inland extent of wetting by the tsunami.

Storm waves, El Niño storms, tsunamis and hurricanes can all cause flooding and
inundation. In the United States, approximately 1% of the population lives in areas that
are at risk from significant coastal flooding from a 1% annual probability of occurrence
event (Crowell et al. 2012). The time and extent of the flooding will depend upon specific
event, bathymetry, overland topography, flooding barriers, and inland structures. If
erosion has also occurred or the seaward area is inundated, these conditions can
exacerbate the flooding impacts. Sea level rise can also exacerbate flooding.

The direct threats from inundation are the permanent wetting of dry land, losses of
agricultural lands or silvaculture production, or conversion of intertidal lands to subtidal.
Drainage systems will have reduced function and low-lying roads or other infrastructure
may completely lose functionality, and can threaten vegetation and habitat. Flooding can
temporarily close down roads or airports, can destroy generators, and damage or destroy
Page 39
building materials and contents, especially if the water remains for more than a few
hours. Tunnels and basements cannot drain naturally, and they will remain filled with
water until pumps can remove floodwaters. Fast moving floodwaters can cause scour that
can destabilize building foundations and pile supports.

Wave Impacts. Wave impacts come during storm events when wave energy is not fully
dissipated in offshore breaking and runup. In general, wave energy increases with wave
height. As a result wave impacts will increase with sea level rise and beach erosion. The
wave impacts, or the pounding of waves against a backshore feature, such as a bluff or
structure can cause bluff erosion, bluff retreat, or structural damage to backshore
development.

3.3 Effect of Climate Change and Sea Level Rise on Coastal Hazards
Climate change and sea level rise provide additional incentive and motivation for most
coastal communities to understand their hazard exposure. Sea level rise alone will, with
certainty, worsen the consequences of storm flooding, wave impacts, and erosion simply
by exposing coastal areas more frequently and more extensively to these hazards. Future
climate-related changes to storms, El Niños, tropical cyclones and hurricanes are a less
certain consequence of climate change and rising temperatures. But, based on the
interactions between water temperature and tropical cyclones and hurricanes, an
intensification of these events with warmer ocean waters is very possible. A greater
frequency or intensity of storms or hurricanes will compound the adverse effects of sea
level rise alone (IPCC 2012; NAS 2013).

Early coastal communities grew during times of fairly static sea level (from about 5,000
years ago to current day, as shown on Figure 3-2); but, trends in global sea level since the
industrial revolution have shown a rise in sea level. During the 20
th
century, global sea
level rise, as seen in Figure 3-3 was approximately 1.7 + 0.3 mm/yr (Church and White
2006). Since 1993, tide gauge measurements, augmented by satellite data, have shown
global sea level rise of 3.2 + -/4 mm/yr (Figure 3-4)
13
. Projections indicate that sea level
will continue to rise, possibly rising by an addition 1.5 to 2 meters by 2100 (Figure 3-5).
Sea level rise is an ongoing process. As noted by Zachary Wassermann, we are now
experiencing “the slow moving emergency of sea level rise” (Wassermann 2014).

13
http://www.columbia.edu/~mhs119/SeaLevel/.
Page 40

Figure 3-2. Post-Glacial Sea Level Rise
Source: Image created by Robert A. Rohde/Global Warming Art
14

14
This figure shows sea level rise since the end of the last glacial episode based on data from Fleming
et al. 1998, Fleming 2000, & Milne et al. 2005. These papers collected data from various reports and
adjusted them for subsequent vertical geologic motions, primarily those associated with post-glacial
continental and hydroisostatic rebound. The first refers to deformations caused by the weight of
continental ice sheets pressing down on the land, the latter refers to uplift in coastal areas resulting
from the increased weight of water associated with rising sea levels. It should be noted that because of
the latter effect and associated uplift, many islands, especially in the Pacific, exhibited higher local sea
levels in the mid Holocene than they do today. Uncertainty about the magnitude of these corrections is
the dominant uncertainty in many measurements of sea level change.

The black curve is based on minimizing the sum of squares error weighted distance between this curve and
the plotted data. It was constructed by adjusting a number of specified tie points, typically placed every 1
kyr but at times adjusted for sparse or rapidly varying data. A small number of extreme outliers were
dropped. It should be noted that some authors propose the existence of significant short-term fluctuations in
sea level such that the sea level curve might oscillate up and down about this ~1 kyr mean state. Others
dispute this and argue that sea level change has largely been a smooth and gradual process. However, at
least one episode of rapid deglaciation, known as meltwater pulse 1A, is agreed upon and indicated on the
plot. A variety of other accelerated periods of deglaciation have been proposed (i.e. MWP-1B, 2, 3, 4), but
it unclear if these actually occurred or merely reflect misinterpretation of difficult measurements. No other
events are evident in the data presented above.

Sources: Fleming, K., P. Johnston, D. Zwartz, Y. Yokoyama, K. Lambeck and J. Chappell. 1998. "Refining
the eustatic sea-level curve since the Last Glacial Maximum using far- and intermediate-field sites" Earth
and Planetary Science Letters 163 (1-4): 327-342.
Fleming, K.M. 2000. Glacial Rebound and Sea-level Change Constraints on the Greenland Ice Sheet.
Australian National University. PhD Thesis.
Milne, G.A., A.J. Long and S.E. Bassett. 2005. "Modelling Holocene relative sea-level observations from
the Caribbean and South America". Quaternary Science Reviews 24 (10-11): 1183-1202.
http://www.globalwarmingart.com/wiki/Image:Post-Glacial_Sea_Level_png

Page 41
The main drivers of changing sea level are thermal expansion of existing ocean water and
increases in the amount of water in the ocean due to melting of land-based glaciers, ice
sheets, and human-caused changes in groundwater pumping and water storage (Chao et
al. 2008; Wada et al. 2010; Konikow 2011). Except for the human-caused changes in
surface water, the sea level drivers are connected with global temperature that is rising
due to increased emissions of carbon dioxide and other greenhouse gases.

The Intergovernmental Panel on Climate Change (IPCC) has become one of the main
international forums for discussions of climate and sea level rise. The IPCC has used
scenarios to develop likely future climate conditions. Their initial assessments were based
upon assumptions of population growth, technological growth and expansion, and
resulting greenhouse gas emission scenarios. The most recent IPCC assessment (AR-5) is
based upon radiative forcing assumptions. The IPPC reports provide likely changes to sea
level, along with many other climate aspects, based on these scenarios. Under the most
optimistic scenarios for emissions and radiative forcing, sea level rise could slow and
stabilize toward the end of the 21
st
century, but under most scenarios, sea level is
expected to continue rising well into the 22
nd
century, so while 2100 is used often as an
endpoint for climate projections, it is really only a point in the continuum.

Figure 3-3. Trends in Global Sea level Rise during the Industrial Era, 1870 to 2010.
Data sources: CSIRO (Commonwealth Scientific and Industrial Research Organization 2009. Sea level rise.
http://www.cmar.csiro.au/sealevel/; and
University of Colorado at Boulder 2009, http://sealevel.colorado.edu.
Trends_in_global_average_absolute_sea_level,_1870-2008_(US_EPA).png

Page 42

Figure 3-4. Global Sea Level Rise Change, 1993 to 2013.
Source: TOPEX satellite (1992-2001), Jason-1 (2002-mid 2008) and Jason-2 (mid 2008-2013). University
of Colorado at Boulder: Sea level change. http://www.columbia.edu/~mhs119/SeaLevel/SL+Nino34.pdf;
last visited 6 Feb. 2014.

Figure 3-5. Various 2100 Global and Regional Sea Level Rise Projections.
Graphic summary of the range of average global and regional sea-level rise (meters) projections by end of
century (2090–2100) from the peer-reviewed literature. Blue boxes are projections developed for coastal
California. Ranges are based on the IPCC scenarios, with the low range represented by the B1 scenario)
and the high part of the range represented by the A1FI scenario. Details on the methods used and
assumptions are in the original references.
Source: California Coastal Commission, Draft Sea Level Rise Guidance, as modified.
0
0.5
1
1.5
2
2.5
Global Sea Level Projections (m)
Page 43
Future sea level is uncertain – some uncertainty is associated with the models and with
ice dynamics, and some uncertainty is associated with future emissions. Research and
better science can help reduce some of this uncertainty, but due to the vagaries of human
actions, a large uncertainty will remain in future water level projections. As shown in
Figure 3-6, water level is the foundation for inundation, flooding, currents, and wave
impacts, so that uncertainties about future water level lead to uncertainties about the
future impacts of those hazards.

Water level uncertainty combines with uncertainties concerning other climatic conditions,
including changes in hurricane and tropical storm frequency and intensity, rainfall and
flooding events, erosion, waves, El Niño frequency and intensity. The result is
uncertainty in almost everything used as input for long-term coastal engineering design.
Engineered structures will continue to be part of the coastal protection, but the
uncertainties in future conditions add to the need for resilient coastal protection that can
adapt to unanticipated events and recover from events that exceed the design conditions.

INPUTS/DRIVERS CONSEQUENCES

Figure 3-6. Trends between Water Levels and Coastal Consequences.
Source: California Coastal Commission, Draft Sea Level Rise Policy Guidance, as modified by R. Flick
and L. Ewing.
Inundation
Erosion,
Flooding,
Wave damage
Thermal changes
to ocean water
Water Mass in the Oceans
Winds, Circulation,
Low pressure systems,
El Niño, PDO
Vertical Land Motion
Seismic & Aseismic
Changes
Tides
Shoreline Change
Tsunamis,
Waves,
Storms
Global Mean Sea Level
Regional Mean Sea Level
Local Mean Sea Level
Local Still Water Level
Local Water Conditions
Page 44
3.4 Risk and Vulnerability
The location of community assets is often a key aspect of vulnerability to coastal hazards.
In general, those assets that are sited on low-lying ground or in close proximity to the
water will be most exposed to coastal hazards.

Historic events can provide communities with good insight into some of the coastal
hazards that are likely and serve as a strong motivation to better understand their
vulnerabilities. Communities can use knowledge of the specific hazards that can occur at
each location within the community to enhance resilience. Certainly, awareness and
understanding of coastal processes are important aspects of risk and vulnerability
assessments as well as for resilience to coastal hazards (see, for example, Cutter 2001; Luers
and Moser 2006; Dengler et al. 2008; US IOTWSP 2007; Courtney et al. 2008). Communities
have little motivation to consider hazard mitigation or resilience, if there is no
understanding that a hazard event is possible or of the different possible risks and
vulnerabilities.

For example, certain atmospheric and oceanographic conditions cause hurricanes and
tropical cyclones to develop and intensify. These conditions then determine where
hurricanes will most likely occur. For example, although climate change may alter the
oceanic locations that have the conditions conducive to foster hurricane development,
hurricanes tend to recur in the same general locations.

It is also possible to have a general concern about risks and vulnerabilities to hazards and
disasters from events that occur in distant, but similar areas. The 1998 tsunami in Papua,
New Guinea, provided motivation for the development of tsunami inundation maps for
coastal California (Synolakis et al. 2002). In addition, the Indian Ocean tsunami that was
generated by the Sunda subduction zone increased concerns in the Pacific Ocean area for
tsunamis from similar subduction zones such as the Cascadia Subduction zone. The
world-wide extent of losses from the Indian Ocean tsunami also focused attention on
studies of the potential consequences of large tsunamis in other ocean basins. For
example, the Indian Ocean tsunami brought attention to earlier work by Ward and Day
that had investigated the structural evolution of the Cumbre Vieja volcano on La Palma in
the Canary Islands and the potential for an eruption and large landslide to generate a
massive, Atlantic-basin wide tsunami (Ward and Day 2001). And, the Great East Japan
earthquake and tsunami caused scientists to reexamine assumptions that had been made
about the event magnitude possible from the Cascadia Subduction Zone.

3.5 Engineering Support for Risk and Vulnerability Assessments
The fundamentals of coastal processes have been the focus of research and study for
years. Tides were some of the first coastal processes to be observed and to have their
forcings identified. In Geography, Strabo repeated material from Posidonius (135-51
BCE) about the motion of the sea: “Now he (Posidonius) asserts that the motion of the
sea corresponds with the revolution of the heavenly bodies and experiences a diurnal,
monthly and annual change, in strict accordance with the motion of the moon”
(Cartwright 1999, pg. 7). The Japanese have also studied and mathematically recorded
Page 45
tsunamis events for over 1200 years (Minoura et al. 2001). Modern wave analysis and
modeling has developed from observations and theory debuted in the 19
th
century.
15

Coastal engineering and research continues to improve both the understanding of
processes and the ways to reduce hazards, risk, disasters and vulnerability. Modeling and
early warning programs have provided powerful tools for community resilience. And,
since much of the large system modeling is linked with the warning systems, these efforts
have synergistic benefits. Coastal process modeling improves the ability to anticipate the
consequences of coastal events and provide a better understanding of the hazard
potentials at a certain location. Modeling can allow for an understanding of very complex
systems and physical phenomena that might otherwise require years of physical scale
model testing and field observations. Some processes present scaling problems that
require compromising the dynamic similarity of one or more parameters, allowing
qualitative analysis of conditions, but limited quantitative utility. An example of this
problem arises with physical models of sediment transport. Reynolds number, using the
dimensionless ratio of inertial forces to viscous forces, is normally used to scale fluid dynamics
problems, where length as the scaling parameter for dynamic similarity. Gravitational force and
the density differences between the fluid and the sediment are important variables for sediment
transport; when waves are scaled by wave length, surface tension often overwhelms gravity.
Options to work around scaling effects can include using a vertically distorted model, changing
fluid viscosity or particle density, but “determining the full-scale values corresponding to the
model results is difficult” (Dean and Dalrymple 2002).

Analytic models also help understand some coastal processes that are not easily or
properly represented by physical models. Recent analytic models efforts have covered
three different and complex geographic scales. The modeling efforts have focused on the
basin-wide models for dynamic events such as tsunamis, tropical storms and hurricanes;
landscape-scale models to better quantify the shore protection values from natural
ecosystems such as mangroves, reefs and wetlands; and, community-scale hydrodynamic
modeling to help characterize the block-by block or parcel-level interactions between
flood waters and the built environment.

Basin-Scale Models and Early Warning Systems: Present day coastal modeling
enables coastal communities to develop detailed maps of the areas vulnerable to
inundation and flooding for a multitude of conditions. For certain large events that
require a lot of computational time for each model run, modelers are now developing a
“library” of synthetic events that can be the used as input when comparable events occur.
Two models, MOST (Method of Splitting Tsunami) by Titov and Synolakis (1998), and
SLOSH (Sea, Lake and Overland Surges from Hurricanes) by Jelesnainski et al. (1992)
have been used extensively to model extreme events of tsunamis and hurricane surge.
MOST provides a useful tool to predict probable tsunami run-up from specified events;

15
19
th
century observations and analyses developed by Russell, Rayleigh, Airy, Stokes,
Boussinesq, Korteweg and de Vries form the foundation for linear, cnoidal, solitons and non-
linear wave theories that are part of modern day coastal engineering models. Modern resources
for information on wave theory include Wiegel 1964; Wiegel 2005; Kinsman 1084; Dean and
Dalrymple 1984; Dean and Dalrymple 2002l Komar 1976; Komar 1998; FEMA 2000; US Army
Corps of Engineers 1984; US Army Corps of Engineers - EM1110-2-1100 N.D.
Page 46
SLOSH models surge for defined geographic basins, taking into account existing gaps for
water to enter the area, barriers, overtopping and overland flows. Both models can rapidly
provide information to emergency managers for early warnings and are powerful tools for
resilience. When a tsunami is generated or a hurricane or tropical cyclone is detected, it is
possible to retrieve the synthetic event or events that most closely approximate the actual
event, scale the potential runup or surge with the appropriate input factors, and provide a
rapid prediction of areas that may be at risk from the oncoming event.

Early warning systems have allowed communities to prepare for disasters in the minutes,
hours or days immediately before the event’s arrival or landfall. In 1900, when a tropical
storm destroyed most of the development on Galveston Island, the National Weather
Service was only 30 years old. Meteorologists around the country would measure
temperature, wind speed and barometric pressure, and sent weather reports to
Washington, DC by telegraph. The only way to track storms over water was from ships,
and few had wireless radios to provide near-real-time weather information. Galveston had
been warned about the tropical storm, but forecasters projected that, after the storm
reached Florida, it would veer east up the Atlantic coast and miss the Gulf Coast (Larson
1999). However, the storm continued to travel northwest, making landfall in Galveston
on September 8, 1900. The Gulf was calm in the morning, yet surged across the island
that night, destroying the city and killing more than 8,000 people. While not a good
outcome for weather service, this event brought attention to the importance of weather
forecasts. Satellites now track low-pressure systems as they cross the ocean, and
forecasting has become fairly accurate. Despite the increase in coastal populations since
1900, the Galveston storm remains the most deadly storm in US history.

Tsunami warning systems took much longer to develop that storm warning systems. In
tsunami-prone areas, people learned the warning signs for a near-source tsunami (a strong
earthquake, rapid withdrawal of the ocean, or a low rumble noise from the ocean). But,
when a tsunami developed away from the coast, there was no warning prior to its arrival.
But, bottom pressure sensors can detect tsunamis and have been used for many years
around the Japan coast for a warning system. In the 1990s, NOAA began installing a
sensor system around the Pacific Rim, called the Deep-Ocean Assessment and Reporting
of Tsunamis (or DART) system, to measure wave amplitudes that can be used to
approximate far-field wave run-up. However, in 2004 there was no detection system in
the Indian Ocean, and news about the tsunami spread too slowly to help in many of the
damaged areas.

Early warning systems can help reduce fatalities and damages from disasters if
information about the approaching events is received in a timely manner. The warning by
itself is of little use if the community does not have plans for using the warning time
efficiently. For example, short-term warnings for near-field tsunamis can provide time for
rapid evacuations, closure of tsunami gates, and can provide for the safe shut-down of
essential equipment. Longer-term warnings can be used to install temporary sand bags,
inflatable vault covers for tunnels, or close storm surge barriers.

Page 47
Landscape-Scale Modeling and Ecosystem Function: Natural systems are clear
components of coastal protection. Offshore reefs and the seasonal cross-shore sediment
transport, where sand builds up on bars during the storm season, protect coastal areas by
causing high energy waves to break farther from the shoreline. Wetlands and mangroves
dampen incoming wave energy; barrier islands blunt storm impacts on the inland areas;
dunes protect inland areas from flooding and high water. Development activities on the
coast have reduced the protective value of many of these natural systems, or communities
have installed built structures to replace the functions of these natural systems. However,
interest in these natural systems has grown, possibly due to an increased awareness of the
many vulnerabilities of the coast; concerns about the loss and degradation of ecosystem
functions; or the growing anecdotal evidence of natural shore protection benefits during
extreme events. Either to emphasis the importance of natural systems to coastal
communities or to bring them into the engineering vernacular, these living shoreline
systems are often called green infrastructure” or “natural infrastructure”, combining their
environmental role with their roles in community service.

Beach and dune systems are prime examples of green infrastructure systems that are now
commonly used for protection of inland areas. Their value develops from moving wave
impacts farther offshore and providing greater distance and elevation for wave
dissipation. Beach nourishment for protection incorporates seasonal beach change and
long-term beach change sufficient to maintain some minimal protective distance.
Nourishment volumes can be incrementally increased to account for increased sea level
rise (Flick and Ewing 2009). The inclusion of dune nourishment can also maintain inland
elevation for flood protection. Extreme events still can overwhelm these protective
features, as seen from Hurricane Sandy damages, but, communities with beach
nourishment and constructed dune (or dunes with a reinforced core) projects had
somewhat less damage than those with no projects (Griffith et al. 2013; Irish et al. 2013).
Models such as GENESIS,
16
SBEACH,
17
MIKE21,
18
XBEACH,
19
can simulate changes
to these protective systems and provide a means to quantify the effectiveness of beach
and dune configurations for a range of conditions.

Many other living shorelines and coastal systems provide wave and flooding protection
through several mechanisms; however, quantification of their protective value is less

16
A model developed by the US Army Corps of Engineers Coastal Hydraulics Institute to portray
long-term shoreline changes resulting from waves and structures or beach nourishment,
http://chl.erdc.usace.army.mil/chl.aspx?p=s&a=Software;34.

17
A model of storm-induced beach change, developed by the US Army Coastal Hydraulics Lab,
http://chl.erdc.usace.army.mil/chl.aspx?p=s&a=Software!31.

18
A suite of coastal models developed by the Danish Hydraulic Institute,
http://www.mikebydhi.com/Products/CoastAndSea/MIKE21.aspx .

19
Developed through cooperation with the US Army Corps of Engineers and Deltares,
http://oss.deltares.nl/web/xbeach/documentation.

Page 48
developed than that for beaches. The complex structure of wetlands, grasses, mangroves
and reefs can attenuate wave energy through drag forces,( Kobayachi et al. 1993; Feagin
et al. 2011.) as well as the bathymetric changes that often occur in conjunction with those
habitats. The protective values will be greatly dependent upon water level and type of
hazard event. Wetlands have been found to provide protection during wave and surge
events, but the protection level can drop significantly when the wetland area is fully
submerged, such as when an area is flooded by a tsunami. However, attenuation will be
highly dependent upon the structure of the system. Usually attenuation increases with
structural complexity and verticality.

Attenuation has been found to exhibit non-linearity where the initial interaction between
waves and the wetland or mangrove causing proportionally more attenuation than the
zone farther inland, calling into question traditional “rules of thumb” which correlate
attenuation or reduction in surge with some travel distance across wetlands (Resio and
Westerlink 2008; Koch et al. 2009; Gedan et al. 2011) Some benefits can result from
small areas of wetlands and mangroves, possibly due to the combined influence of the
vegetation and associated bed elevation; but, the density of vegetation is also important.
Marshes also help reduce inland erosion, with evidence often found only following the
removal of marshes, when erosion accelerates rapidly.

Quantification of wave reduction and attenuation varies greatly. In theory, permeable
oyster reefs can potentially attenuate wave heights by up to 95% (van der Meer et al. 2005;
Cheong et al. 2013); however, in pilot studies of two constructed reefs, the structures
rapidly experienced a drop in elevation and an expanded their footprint when exposed to
routine wave events. The constructed reefs provided good ecological benefits, but little
shore protection (Scyphers et al. 2011). McIvor et al. (2012) estimate a reduction in
wave height between 13% and 66%, when routine waves pass through only a 100 meter
wide section of mangroves; however, such reductions are for small wind waves.
Mangroves’ protective benefits for waves, while important for small and moderate
events, (Gelfenbaum et al. 2011; Hashim et al. 2013) is expected to be fairly minor for
major events, depending upon distance from the source and characteristics of the
mangrove stand (Cochard et al. 2007). Fritz, as reported by Verhagen and Loi noted that
large expanses of coastal mangroves, forests and other vegetation were completely
uprooted and destroyed by both large and moderate tsunamis (Verhagen and Loi 2012).
Page 49

Figure 3-7. Remains of tsunami forest in Rikuzen Takata, Japan, May 2011.

It is unlikely that the protective values of ecosystems can ever be characterized in a
manner that is parallel to an engineered structure; nevertheless, their protective values
cannot be overlooked. Better and more quantitatively consistent monitoring of living
shoreline and ecosystem areas will improve the ability to put ranges on their protective
capacity (Walker et al. 2011). And, as noted by the US Army Corps of Engineers (2013),
“coastal risk reduction can be achieved through a combination of approaches, including
natural or nature-based features”. Natural infrastructure offers storm damage reduction
and potential risk reductions. More effort is needed to quantify site-specific risk
reductions and to better link green and grey infrastructure options, through better
monitoring and analysis (Spaulding et al. 2013). In addition to the risk reduction
properties of these natural systems, they also offer the resilience potential of self-healing
and self-maintenance.

Community-Scale Modeling: One of the more challenging aspects of coastal modeling
is the movement of water through the surfzone and on to land. As noted by two esteemed
coastal scientists, Drs. Synolakis and Bernard, “the evaluation of terminal effects of
natural hazards remains one of the holy grails of geophysical research” (Synolakis and
Bernard 2006, pg. 2231). However, the on-land and overland flows are the critical
aspects that determine most community damage from coastal events. Urban areas along
the coast have the added challenges that there are many different barriers to waves and
flooding, including natural features and engineered structures. Urban areas present
difficult terrains to model correctly, due, in part, to the abrupt changes in elevation. Also
inland buildings, roadways, and drainage systems can divert or channelize overland
flows, protecting some areas from flooding and intensifying flood problems for other
areas. There have been several levels of modeling flooding at the community scale, from
general efforts to the fine scale.

Concern about sea level rise has been a key motivation for many of the recent coastal
flood modeling efforts. These modeling efforts support planning for coastal hazards at
Page 50
varying geographic scales, for different purposes, and for different users. Some coastal
flood modeling efforts have examined current and future flood risks for broad geographic
areas. These models often will establish a potential future water elevation by making
assumptions about tides, waves, and sea level rise, and considering all coastal lands
below this identified elevation to be potentially at risk.

Many of the so-called bathtub models have been developed using this approach. For
example, the Dynamic Interactive Vulnerability Model, DIVA model, provides analysis
at the multi-national, national or large region scale on areas of potential flooding and
people in the potential flood zones, derived from very coarse scale topography and asset
locations (Vafeides et al. 2008). While useful for providing a global or national
perspective on flooding and sea level rise, these models do not help individual
communities assess current or future risks. In the US, sea level rise viewers have been
developed that allow the user to set a future water level from a combination of tides,
atmospheric forcing, waves and sea level rise
20
. The viewer will show the areas that both
have a clear connection to the ocean or bay and that are lower than this elevation.

Generally, sea level rise is included into flood models at one of two points in the analytic
process. Some models add sea level rise into the final result, and others as one of the
driving forces. The former is often done when areas at-risk from flooding areas have
already been modeled, and the effects from sea level rise are added to the existing flood
risks. For example, Heberger et al. (2009)

added sea level to existing flood elevations to
identify critical structures along California’s ocean coast that could be at risk from
potential sea level rise. The latter often requires more modeling effort, but it is a more
realistic representation of wave driven flooding. Kanoglu and Synolakis (1998) have
shown that small changes in sea level in front of a structure can have large changes in
long wave, tsunami runup.

Following Hurricane Sandy, NOAA, FEMA, and the US Army Corps of Engineers
developed a flood viewer for advisory coastal hazards for New York and New Jersey that
show were based on an existing base flood elevation with 1, 2, and 3 feet of addition
water depth added to the inland flood zone to represent possible changes in flooding due
to sea level rise.
21
For modeling of flooding in San Francisco Bay, Knowles (2009)
introduced the elevated water levels from sea level rise into the boundary conditions.
Process-driven models, such as the Coastal Storm Modeling System (CoSMoS) that was
developed for the highly energetic Pacific Ocean wave conditions, include changes in sea
level to the initial driving conditions, so that the evolutionary bathymetrical
transformations are applied to the propagation of sea level modified waves (Barnard et al.

20
Two examples are the NOAA Sea Level Rise and Coastal Flooding Impacts Viewer;
www.csc.noaa.gov/slr; and the Climate Central’s Surging Seas Risk Finder;
www.sealevel.climatecentral.org; both last visited 12 May 2014.

21
Advisory maps for New Jersey and New York following Sandy can be found at
http://geoplatform.maps.arcgis.com/home/item.html?id=2960f1e066544582ae0f0d988ccb3d27 ;
details on mapping also at: http://www.globalchange.gov/what-we-do/assessment/coastal-
resilience-resources.
Page 51
2009). This type of wave representation is likely to be important at locations where there
will be standing water at the toe of the protective structure, since it will insure that the sea
level modified wave is included in the runup analysis, or where small differences to water
levels will determine whether or not an area will be flooded. FEMA has initiated a study
to compare the results from these two techniques for different types of shoreline to
determine whether and when the inclusion of sea level rise as part of the driving force is
worth the added time and when the additive method is “good enough”.
22

Flood modeling often do not include hydraulic connectivity in the modeling. As a result,
low areas, even if protected by berms or levees, may be identified as being potentially
flooded. Some models identify potential flooding areas without including information
about whether the area will be inundated throughout the tide cycle or only flooded for an
hour during the highest tide. By looking at changes in water level, without inclusion of
shoreline change, these models can provide approximations of future flood conditions
that are tied to sea level rise alone, rather than identifying a specific time period for
concern. If shoreline change is not considered in the analysis, the coastal impacts from a
0.5 meter rise in relative sea level (resulting from either an increase in water level or a
decrease in land level) would be the same if that rise were to occur in 2050 or 2100.
These efforts, while representative of the general flood conditions for the community, fail
to account for changes to the shoreline due to erosion or accretion, or for many of the
existing community features that modify current and future flood risks.

Modeling at the parcel scale has many data-related challenges. Detailed water-side
modeling is needed to generate the flood forcing, and modeling the overland flooding
requires detailed information on the topography and sub-surface hydraulic connections.
Bare earth elevations are needed, (Sanders 2007; Begnudelli et al. 2008) along with detailed
measurements of levee and bulkhead elevations and identification of building locations.
Bare earth or ground elevations can be extracted from LiDAR data, but often the
elevations of protective structures need to be taken from measurements in the field and
added into the ground topography, (Gallien et al. 2013) making the initial data
development very labor-intensive. But, as noted by Schubert and Sanders (2012), urban
areas can be represented by a variety of unstructured mesh models with fairly good
results, including velocity differences at the building-scale if building geometries are
specified. Detailed local flood models, despite the intense data needs, can be very useful
in the analysis and development of cost effective adaptation strategies. Advances in
modeling building-water interactions and to properly account for the varying water levels
are extremely important for improved flood modeling. Field investigations of tsunami
damage areas found that buildings in the lee of larger buildings often survived better than
their unsheltered counterparts (Dalrymple and Kreibel 2005; Synolakis and Kong 2006).
In post-hurricane investigations, inland water areas were also observed to modify
flooding differently than vegetated land (Edge and Ewing 2013).

22
Personal communication from Ed Curtis, PE, Risk Analysis Branch, FEMA Region IX.
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Already, existing protective structures often maintain little, if any, freeboard during high
water events. This has been demonstrated through the “King Tides” initiative
23
that
provides photo documentation of present day flood conditions during extreme high tides.
In local flood modeling, flood predictions are very sensitive to both water and barrier
elevations, and situations where flood waters are at or near the threshold for overtopping
are some of the most challenging efforts for local flood modeling. Gallien et al. (2013)
recommend using barrier elevation surveys with a root mean square error less than ~1cm
for flood models of locations with 1 – 2 m tidal amplitudes. In seismically active areas, or
areas with land subsidence, such elevation resolution would require regular resurveying,
and when used for modeling of future sea level rise that can have ranges between 0.5 and
2.0 meters. Attention on centimeter level survey accuracy may be mis-focused.

Engineering models, often supported by field investigations to provide information on
water levels and run-up for known driving forces, are valuable tools for a broad range of
coastal hazards. Models can directly influence some community vulnerabilities, as for
example, their use in early warning and evacuation. Engineering models also help
improve the understanding of hazard concerns, ranging from the large, state or national
scale to the landscape, block, and parcel scales. This understanding of hazards is an
important aspect of coastal disasters and actions leading to improved resilience.

3.6 Risk and Vulnerability Assessments for Community-Scale Resilience
Basin-, landscape-, and community-level modeling efforts can inform communities about
the extent of inundation, flooding, wave impacts and erosion for various hazard events or
combination of events. These models can also be used to determine the likely
consequences of future increases in sea level, or changes in the effectiveness of various
protective features, additions or modifications to the existing protective options. Risk and
vulnerability assessments combine with modeling of coastal processes with information
about where key assets are located to determine what assets might be exposed to various
hazards, whether the assets would be sensitive to or affected by the exposure to some
hazard, and then the consequences of changes to the type or location of the key
community assets for increasing or reducing risk and vulnerability.

Risk and vulnerability assessments are powerful tools to guide community development
and resilience. As a first step, they help identify at-risk facilities and groups within the
community and determine the facilities and groups that need greater resilience. Risk and
vulnerability assessments can also help with decisions to increase resilience such as
where to locate new facilities; when to upgrade, enhance, or expand existing natural and
engineered protection; when and where to add new protection; or, where to establish
warning sirens, evacuation routes and evacuation shelters.

23
King tide, originally used in Australia, is a non-scientific term for the highest high tides of the
year. Since 2009, citizen activists have used photographs of the tide events to provide visual
images of the water levels that might become normal with rising sea level. Photos are collected
through: http://kingtides.net/, as well as a number of more local programs.
Page 53
Risk and vulnerability assessments must be based on some information of where at-risk
populations or assets are located. For example, flood modeling may determine that waves
from a 100-year storm could flood all development that is situated on land lower than
+2m MHW and within 250 meters of the shoreline. But only with knowledge of the type,
intensity and location of the development can the community determine the risk and
vulnerability of this flood condition. The flooding would occur, whether the land is used
for agriculture or if a school and hospital have been built there. The consequences of the
flooding, in terms of fatalities, property losses, and business disruptions will be quite
different too and depend upon the land uses in the at-risk areas. Specific consequences
may not be determined even knowing the type of land use, since, for example, rice fields
may easily tolerate flooding during the early part of the growing period, but may be very
sensitive to excess water later in the growing season. Construction methods, such
elevated building foundations, can modify building exposure and sensitivity to flooding.

One type of risk and vulnerability assessment considered the number of people and types
of assets that are located within specified areas, often identified by elevation or proximity
to the coast. For example, the discussion of the people and assets that were located global
between MHW and +1-m, +5-m and +10-m MHW was from this type of assessment. No
information is provided about when these people or assets will be exposed to hazards or
when sea level rise will worsen the existing hazards; the assessment frames the reason for
concern based on the exposure to the specified conditions. An assessment of the 100-year
flood exposure provides information on the people and assets and risk from an event with
a specific probability of occurrence. Other approaches to risk and vulnerability
assessments examine specific type events, such as storms or tsunamis coming from the
south or the north and can be useful for coastlines with headlands or offshore islands that
protect communities from waves approaching from certain directions. Such studies might
not alter development patterns, but might influence deployment of temporary protection
and focuses for evacuation, based on the type of event that is approaching a community.

Climate change and sea level rise have put new emphasis on risk and vulnerability
assessments, since historic hazard information may not fully encompass future risks.
Several of the hazards may themselves change in frequency or intensity due to climate
change. Rising sea level will exacerbate existing consequences by moving the forces
higher on the beach or shoreline and farther inland. Nevertheless, the risks from or
vulnerabilities to future hazards, with or without sea level rise, will be determined by the
hazards and the assets that will be exposed to the hazards. Sea level rise may threaten or
exacerbate the threats to low-lying agricultural lands, low-lying development and shallow
groundwater wells. However, the actual risks and vulnerabilities will be based upon
community development patterns and construction methods.

Shore protection can greatly affect what areas are exposed to various coastal hazards.
Yet, this protection is provided to the location and it does not depend upon what is being
protected. For example, a levee will block floodwaters, whether the levee is surrounding
an agricultural parcel or a housing complex. The agricultural land or housing complex
may be less vulnerable to flooding because the levee is there; however, the protection is
independent of what is protected. A community may decide to focus on the maintenance
Page 54
of levees that protect a housing complex to reduce possible flooding exposure of the
housing complex. No generic risk or vulnerability characteristics can be ascribed to
coastal protection measures; all characteristics are associated with what is protected.

The main value of risk and vulnerability assessments for community resilience is in the
identification of areas and assets that are at-risk, and the opportunity to evaluate various
decisions for how they could change likely disaster losses. The main focus for these
studies is on the event portion of resilience, or the initial amount of loss that results from
a tsunami, hurricane, storm or other coastal event. There are many ways these
assessments can help inform options for improved community resilience. For example,
these assessments are valuable for resource allocation decisions, such as planning long-
term investments in new infrastructure, when developing budgets for maintenance of
protective structures or projects that can enhance natural protective elements, or applying
for various grants to develop green infrastructure or living shorelines. These assessments
do not change consequences; but, they do help communities understand possible risks
and to make decisions on future development patterns and investments that are informed
by these risks.
Page 55
Chapter Four
Disasters – Lessons for Resilience

Floods are “acts of God” but flood losses are largely acts of man.
Gilbert White, Human Adjustments to Floods, 1945

4.0 Introduction
Disasters can overwhelm a community or region, causing loss of life, damage to
buildings, infrastructure and the environment, and interruptions to normal community
activities. But, disasters also provide full-scale experiments to allow researchers to study
how structures respond to large forces; determine what structures survive, what structures
fail and why; and identify commonalities in failures and survivals across different
structures, communities and types of disasters. This chapter discusses several of the
recent large coastal disasters, observations from field investigations of several disaster
areas, and a summary of lessons learned from these field investigations, drawing upon
published reports from these recent disasters and direct field observations.

4.1 Coastal Disasters
Disasters are events that disturb a community. In the first 13 years of the 21
st
century,
there were over 1700 presidentially declared disasters in the US and 226 of these were
coastal disasters,
24
or 13% of all disasters. By comparison, there had been 3,427
presidential disasters since 1953, when President Eisenhower first issued a disaster
declaration for tornado damage in Georgia (Lindsey and McCarthy 2012). Only 13% of
these 3,427 events were clearly coastal (designated as coastal storms, hurricanes/tropical
storms, tsunamis or typhoons), this is the same percentage as that for the time from 2000
to 2013
25
. However, the number of declarations and coastal declarations has increased
significantly since 1953. Half of all declarations made in the past 60 years have been
made since 2000. Some of the increase in declarations may be attributed to the increased
population in higher hazard areas, including the coast. In 2011, prior to Hurricane Sandy,
there were over $500 billion US FEMA insured assets in identified coastal floodplains.
When costs for all contents of structures, living expenses and business interruptions are
included, this estimate would exceed $10 trillion US
26
. As noted by the Heinz Center (H.
John Heinz III Center 1994, pgs 23 – 24.):

24
Based on FEMA disaster declarations, by year, http://www.fema.gov/disasters/grid/year, (last
visited 25Jan2014). Coastal disasters are limited to those identified as coastal storms,
hurricanes/tropical storms, tsunamis and typhoons. Also, the Declarations do not correspond to
individual hazard events since multiple declarations can be issued if different areas experience
damage from the same event.
25
Based on analysis of disaster declarations from FEMA,
http://www.fema.gov/disasters/grid/year, last visited 25January 2014.
26
NOAA’s State of the Coast, http://stateofthecoast.noaa.gov/insurance/welcome.html, and AIR
Worldwide, 2013. The Coastline at Risk: 2013 Update to the Estimated Insured Value of U.S.
Page 56

Coastal development also has become a lucrative economic force for
private investors. The deluge of people living on and near the coasts is not
merely a fad that soon will yield to a preference for inland locations. It is
largely a result of population growth combined with the beauty and
economic promise of coastal areas. This growing interest in coastal
development, combined with a strong economy, in recent years has
increased the pressure on landowners to sell or develop.

Regardless of the incentives for coastal development, coastal disasters have been a
serious problem for the US and other coastal nations. They have resulted in numerous
injuries and fatalities, extensive property losses and business interruptions. Some recent
coastal events have been carefully investigated to better understand the underlying
physical processes causing the damage, identify the strengths and weaknesses in the
engineering systems, and develop ‘lessons learned’ that can help improve resilience to
future events.

4.2. Investigations of Recent Coastal Disasters
Post-disaster field investigations have been one of the most powerful tools for assessing
coastal resilience (Synolakis and Okal 2005). Computational models are also important
predictive tools; however, their results are limited by the physical parameters that are
included in the model, and they rarely replicate exactly real world events. After tsunami
waves up to 10 meters in height struck Sissano Lagoon, Papua New Guinea, model
analysis of the earthquake as the source for the tsunami could not replicate the waves,
orientation, timing, or height that actually occurred. Field investigations and bathymetric
surveys of the surrounding area identified a recent underwater slope failure that had not
been included in the model. Later modeling used the landslide as source, and it was able
to fairly closely reproduce the observed waves and support the landslide as the
mechanism for generating the large localized tsunami (Synolakis et al. 2002).

Field investigations are invaluable for examining the consequences of extreme coastal
events, and providing data that can be used to verify or recalibrate models, and for
providing new understanding of generating mechanisms that necessitate new model
approaches. Also, most field investigations examine the on-land component of a coastal
event, where the coastal forces are transferred to terrestrial or constructed systems. This
transition zone is the most difficult to include in analytic and physical models, except for
those times when nature uses the coast as a full-scale laboratory.

Indian Ocean Tsunami, December 26, 2004. The Indian Ocean tsunami was caused by
the subduction of the Indian Plate under the Burma Plate in the vicinity of Sumatra and
the Andaman Islands. Within hours of the initial earthquake, the tsunami had propagated
throughout the basin, causing death and destruction in 16 different countries. Following

Coastal Properties, https://www.air-worldwide.com/publications/.../the-coastline-at-risk-2013,
(both last visited 25Jan2014).
Page 57
the event, numerous teams of researchers traveled throughout the impact areas to obtain
measurements of inundation, flooding, and run-up for use in model calibration, and
assessments of structural and infrastructure damage for use, in turn, in rebuilding plans
and future building codes. Observations by survivors were documented as well. And, this
was one of the first events for which there was video footage that could be used to
estimate velocities, eddy currents, and scour (Fritz et al. 2006). Dozens, if not hundreds
of reports and assessments were prepared for a broad range of interest groups, from aid
and health care groups to engineers and geophysicists.

Synolakis and Kong (2006) prepared a summary of field investigations from the countries
that suffered damage from the Indian Ocean tsunami, providing a wide array of
observations that contribute to improved tsunami resilience. Dalrymple and Kriebel
(2005), one of the teams of engineers that participated in the Indian Ocean field
investigations prepared a review of performance of buildings and shore protection. They
observed that many of the reinforced concrete, well-engineered buildings fared well, but
scour was a significant problem for buildings with shallow foundations. Dalrymple and
Kriebel also found that building elevation, a pass-through lower floor and orientation
with the short building dimension to the water were other predictors of building
survivability. They also noted that scour was a significant problem for much of the
infrastructure that experienced problems, failure or instability. Well-designed seawalls
provided some protection to inland property; and even some low structures provided
protection by redirecting wave momentum away from the inland buildings (Dalrymple
and Kriebel 2005, pg. 9). But the tsunami also exposed weaknesses in many structures.
For example, a poorly constructed sand bag core seawall on Phi Phi failed in many places
due to scour, and thus, it provided little, if any, protective value before collapse
(Damrylple and Kriebel 2005).

Natural features were identified for their protective values in many areas. On Karon
Beach, a low-elevation sand dune greatly dissipated the wave forces so that the inland
development experienced high water levels without the damages from high velocity. This
area stood in sharp contrast to a beach where the fronting dune elevation had been
lowered to improve ocean views and the inland hotel was completed destroyed
(Synolakis and Bernard 2006). Liu et al. (2005) observed that mining of coral from the
nearshore in Sri Lanka likely contributed to the inland penetration of waves; the Samudra
Devi passenger train, the location of over 1,000 fatalities after the tsunami force was
sufficient to derail the train cars, was inland of the location where the reef mining had
occurred.

Hurricane Ike. Hurricane Ike was a Category 2 storm when it made landfall on
September 13, 2008. Ike headed up Galveston Bay and the bulk of the storm force bore
down on the Bolivar Peninsula to the east of hurricane eye. Most of the development on
Bolivar was destroyed; approximately 3,600 buildings were significantly damaged or
destroyed on the east Texas coast. On Galveston Island alone, 1,261 buildings were
damaged or destroyed (Edge and Ewing 2013). Most of the damage to Galveston
resulted from bayside flooding.

Page 58
After a tropical storm destroyed most of Galveston in 1900, the city took several steps to
better prepare for future storms. The city was elevated to 5.1 meters near the seawall,
sloping down to 2.4 meters over most of the residential areas. The city also built a
massive concrete seawall 5.2 meter high, initially protecting the 4.8 kilometers of the
downtown (Wiegel 1991) and eventually extending 16 km to the west (Hansen 2007).
During Hurricane Ike, the seawall provided flood protection, but the western end of the
seawall was damaged, and the beach suffered significant erosion. Hurricane Ike also
destroyed all the Gulf-side piers and damaged several of the Gulf-side groins.

Prior to Hurricane Ike the beach areas west of the seawall had experienced significant
erosion of about 1.65 m/yr (Morton and McKenna 1999), with erosion occurring often
during storms. Communities on western Galveston Island that were not protected by the
seawall experienced significant erosion and flooding. Some communities had installed 1
to 2 meter high dunes with a geotube core (Figure 4-1). Waves washed over the dunes,
destroying or deflating the geotube cores, and damaging inland development.

Figure 4-1. Remains of Geotube Dune Protection installed at Galveston, TX.
Prior to Hurricane Ike, the geotubes were covered with sand as part of a dune system.
Source: Author’s Collection, taken 4 October 2008, about one month after Hurricane Ike.

A recent field investigation of the Galveston area following Hurricane Ike included
observations of hurricane surge that compare with observations of tsunami damage by
Dalrymple and Kriebel (2005); that the elevation of buildings and shore protection were
critical to survival of developed areas; that scour was one of the major factors that
destabilized both shore protection; and, that buildings with poorly embedded foundation,
as shown in Figure 4-1, were at risk from both wave impacts and scour (Ewing et al.
2009).
Page 59

Following Hurricane Ike, most ground transportation and communications were back in
service within about a week; power lines had been replaced within the month; and, debris
clean-up and water line replacements took several months. Temporary housing was
available within a few weeks, but permanent housing had not been fully restored even a
year after the event (Ewing and Synolakis 2011).

Figure 4-2. Scour Damage at Sea Isle Beach, Galveston, TX
Source: Author’s Collection, taken 4 October 2008, about one month after Hurricane Ike.

Samoan Tsunami. On September 29, 2009, a strong submarine earthquake shook
American Samoa, Samoa, and other island nations in Polynesia. The epicenter was
between Samoa and Tonga and within about 20 minutes of the earthquake, tsunami
waves began to arrive on Tutuila, the main island in American Samoa. Over 56,000
people live in American Samoa and there were 34 fatalities from the tsunami.

Tutuila Island is an ancient volcanic island. The coastline is very rugged, with small
coves and pocket beaches along the shore; a fringing reef rings much of the island and
provides some protection to the island from rather frequent tropical cyclones and storms,
and the less frequent tsunamis. Pago Pago, the capital city, is situated on a natural deep-
water harbor on the southern coast of the island.

Tsunami runup varied greatly around the island and some of the highest observed runups
were along the central section of the coast, as well as the east and west ends of the island.
Paloa, a community on the western end of the island had the largest observed runup of
17.6 meters (Okal et al. 2010). All the low-lying development near the beach were either
destroyed or greatly damaged. A small revetment and a gabion wall structure had been
Page 60
constructed along the shoreline. Waves washed over the revetment without any indication
that the wall altered the wave run-up. The shoreline remained stable; however the small
bluff inland of the gabion structure was eroded. Despite the extensive damage to the
community, residents recognized that the earthquake might have triggered a tsunami and
evacuated the low-lying area. Hence, there was only one fatality in this community.

Figure 4-3. Paloa, American Samoa. Damages from 29 Sept. 2009 Samoan Tsunami
Source: Author’s Collection, taken 27 October 2009, about one month after the tsunami.

The interior part of the island is very steep and most transportation facilities are
concentrated along the coast. A large, engineered revetment protected the roadway near
Pago Pago, and the only damage to transportation facilities came from debris being
washed onto the roadway and airport runways. Vehicle traffic was able to resume once
the debris was cleared. The main power plant for Tutuila was located in the inundation
zone in Pago Pago; the diesel generators were flooded by salt water, shutting down the
plant and leaving most of the island without power. Emergency generators were quickly
brought to the island, set up at dispersed sites around the island and power was restored
within a few weeks. Within a month after the tsunami, most services were restored,
although clean-up activities took several more months. However, a large amount of
debris was washed offshore and onto the fringing reef, degrading this habitat area.

Tohoku Tsunami, Japan. The Tohoku Oki or Great East Japan, a magnitude 9.0
subduction earthquake, generated a basin-wide tsunami on March 11, 2011. Within about
25 to 30 minutes tsunami waves struck the coast of northeast Japan, within 8 to 12 hours
waves struck the coasts of North and South America and wave damage was even
observed in the Antarctica (Brunt et al. 2011). Runup along much of the East Japan coast
exceeded 15 to 20 meters, with maximum inundation of about 40 meters near Yamaha
(Sato et al. 2011).

Page 61
Damage to the Fukushima Power Plant resulted in rolling blackouts throughout the
region. Water supplies were disrupted, with over 1.6 million households and 187
municipalities suffering from water outages soon after the event. Damages from the
tsunami were extensive. About 15,550 people were killed in Japan, more than 100,000
homes were destroyed and damages exceeded $150 billion US. Many kilometers of roads
were damaged; 77 bridges were damaged or destroyed; 25 levees failed; over 750 levees
had settlement, slumps or cracks; and, almost 400 walls and gates were damaged
(National Policy Academy of Japan 2011; Harder et al. 2011). Many of the coastal
protection structures were damaged or destroyed; tsunami barriers were overtopped; the
inland areas were damaged by tsunami waves, and once overtopped, many of the
structures experienced damage on the inland side.

4.3 Lessons for Coastal Protection and Resilience from Recent Disasters
The field observations of these disasters have had many useful results. The runup
measurements have been used for model refinement. Some of the observations from the
Indian Ocean tsunami provide guidance on the types of engineering structures that might
survive a future tsunami event. Putting aside the questions about rebuilding in the most
heavily impacted areas, observations of building survival have served as models for
vertical evacuation options for already built communities. Design guidelines for vertical
evacuation structures have since been developed along with a companion report for local
government planners (FEMA 2008b; FEMA 2009). As a result of the field observations
from Hurricane Ike, the Federal Emergency Management Agency (FEMA) revised its
direction for scour, pile design and embedment depths (FEMA 2008a). Work is now
underway to incorporate tsunami forces into ASCE design standards, relying to a large
extent upon the field measurements from the Indian Ocean, Chilean, and Great Tohoku
tsunamis.

Successful designs provide clues for future successful designs, but so too do failures and
failure consequences. The Kamaishi Breakwater in Japan, despite significant collapse of
the superstructure, provided protection to the inland community; many other structures
provided no community benefits following their damage or collapse. These different
consequences of failure also help inform plans for future resilience. No one event will
provide all the solutions to coastal disasters and community resilience, but it can be
hoped that each future event will spur incremental improvements.

As will be discussed further in the next section, resilience is not just important at the
moment of the disaster, it is important through all phases of a disaster. For example, the
north east coast of Japan is subject to tsunamis such as the Tohoku event, as well as
typhoons and massive storms. Communities with intact protection could undertake
cleanup and rebuilding with less concern vulnerability to annual or decadal scale storms.
While the resilience to the extreme Tohoku event exposed weaknesses in community
protection, the post-event resilience was far better from those communities with the intact
protection than those without any protection from future events. In addressing resilience
to coastal disasters, there are four distinct phases to disaster response – pre-event, event,
Page 62
event response, and event recovery and these are discussed further in the following
section.

For many coastal communities, engineering structures are major aspects of community
protection and disaster resilience. These structures provide resistance to the hazard
forces, either by blocking the hazard with a physical barrier or by reducing the incoming
forces. Structures such as surge barriers, seawalls, and levees provide protection from
inundation and flooding by providing physical barriers between the water and the inland
assets. Structures or features such as breakwaters, revetments, berms, and dunes reduce
incoming wave energy.

Designers and engineers require some information about the incoming water for the
design of physical barriers, since the barriers need to be higher than the incoming water
to be effective. The recent coastal disasters have provided a key lesson that height and
elevation are essential aspects of a barrier’s effectiveness (Damrymple and Kriebel 2005;
Ewing and Synolakis 2010). The effectiveness of all the protective structures and features
also depends upon their structural competence. The height of a structure will be of no
importance if the structure has collapsed. General observations from post-disaster field
investigations are that well-engineered structures often survive an extreme event
(Synolakis and Bernard 2006). Engineering details that help hold a structure together
during flooding or overtopping are a solid foundation that is either deeply founded or
anchored into bedrock; strong connections between elements (three-point contact for
revetments or armor units, mechanical connections between concrete panels, caissons,
wall segments, etc.); and walls that are tied into rock outcrops or a highly erosion-
resistant material (ASCE-COPRI-PARI 2013; Ewing and Synolakis 2011).

Elevation: The value of elevation is a lesson from almost every disaster where water is
the main source of damage and destruction. Elevation above the maximum water level
can keep people and property away from the most dangerous parts of the event.
Hurricanes Katrina, Ike and Sandy and the Tohoku tsunami have all provided reminders
of the dangers of placing buildings, utilities and power supplies within reach of storm
waves or tsunami wave runup. However, one key lesson in resilience is that if the lowest
floor members are above the elevation of waves and flood-waters, many buildings can
survive (Ewing et al. 2009). Roadways may be the one exception, where at-grade roads
tend to experience less damage during flood events that do elevated roads, possibly
because the elevation difference sets up a hydraulic jump that can scour the roadbed as
the floodwaters recede (Ewing and Synolakis 2011).

Elevation can provide protection in different ways, with elevation of the protection
features used to protect land and development inland of the structure, or elevation of the
individual structures used to protect those buildings. Even small shore protection can
provide some protection if it stays intact. In Thailand, a low seawall was able to dissipate
some of the wave energy from the Indian Ocean tsunami. Inland structures suffered from
flooding, but were protected from wave forces (Damrymple and Kreibel 2005). Sand
dunes provided similar protection to inland development on Phuket, where development
inland of intact dunes experienced only a gradual rise in water level, and development
Page 63
inland of an area where the dune had been lowered to provide been views of the ocean
(Synolakis and Bernard 2006). Overland penetrations of waves in Sri Lanka were
observed to be greater inland of areas where coral had been mined from the offshore reef
(Liu et al. 2005).

Much of downtown Galveston was protected from erosion and flooding by the Galveston
Seawall. Other parts of the Galveston coast had been protected, ineffectively, by low-
crested geotube berms; however the berms were not high enough to protect inland
development (Ewing et al. 2009). In Samoa and American Samoa, protective walls
reduced erosion and scour; however, an under-designed revetment on Upolu was
destroyed and the revetment stones became projectiles that damaged inland development.

Scour. Scour, the removal of sand or bed material from the vicinity of a coastal structure,
is a well-recognized problem for structures exposed to high-energy water or fast currents.
Despite being well-known, scour is the source of many structural failures, focusing often
at the corners or edges of structures or at areas of flow convergence. Failure or complete
collapse of structures can originate from scour hotspots (Ewing et al. 2011; Edge and
Ewing 2013). General beach scour, or the drop of beach elevation, can also be damaging
to buildings. The drop in beach elevation will reduce wave attenuation, and let larger
waves propagate farther inland (Ewing and Synolakis 2011). Scour can be damaging to
structure foundations that are not deeply embedded, Scour aprons and well-embedded
piles can help reduce structural damage from scour impacts.

The Importance of Engineering Details. Water and waves can find small weaknesses in
engineered elements, such as connections, joints, corners, tie-ins, and contact points, and
propagate small weaknesses into progressive losses or larger failures. Many of the
failures of protective structures that were destroyed by the Tohoku-Oki tsunami seemed
to have developed from small weaknesses. Connections between segmented tsunami
walls, as shown in Figure 4-4, were insufficient to hold segments together once small
gaps developed. Some dike failures likely started with the buildup of hydraulic pressure
that dislodged one or two inland panels. The loss of one or two panels would reduce
stability of surrounding panels, and overtopping would scour the underlying fill, remove
more panels and rapidly reduce resistance to lateral loads. While the actual failure might
have been from the lateral forcing, the reduced stability from loss of panels, overtopping
and scour contributed to the collapse (ASCE-COPRI-PARI 2013). Unless sections are
isolated by internal cells or walls, the loss of one wall or levee segment can weaken
adjacent sections, leading to cascade failure.

Page 64

Figure 4-4. Seawall Failure at Koizuma Beach, Japan.
Sections of wall were connected by small reinforcing bars; walls failed at these
connections.

Contingency Planning – Examining What-if Situations. One main lesson from disaster
investigations is that it is important to consider the consequences of the disaster event
exceeding the design conditions of the structure. The Tohoku tsunami waves were higher
that most of the barriers that had been constructed for tsunami and cyclone protection
overtopping had not been considered in the design. When the walls were overtopped, the
walls had no protection from inland scour (ASCE-COPRI-PARI 2013). More walls might
have survived, if there were scour protection and inland stability, reducing loss of
structures after overtopping.

The concept of contingency planning is to reduce unanticipated failure or having one
point of failure lead to complete structural collapse. Contingency planning normally
starts with scenario-based analysis of risk and vulnerabilities and it attempts to look at
possible failure modes and ‘tipping points’ such as breaches, foundation instability or
overtopping that might propagate additional failures. Structures cannot be designed for all
possible extreme events; however, contingency planning examines the possible
consequences that can result from exceedance of the design conditions (ASCE-COPRI-
PARI 2013). Such planning can lead to structural designs that control small failures and
prevent them from growing into major collapses.

Adaptation planning has been developed for dealing with the uncertainties of climate
change and sea level rise and is closely related to contingency planning. Similar to
contingency planning, adaptation planning often develops from scenario-based analysis,
with the scenario analysis developed from possible amounts of future sea level rise. The
design will be based on some assumed sea level rise amount. If a higher amount of sea
level rise could jeopardize the structure, the idea with adaptation planning is that options
will be included to allow structural modifications if sea level rise is larger than what was
used in the design. In other situations, redundant structures might be more effective than
Page 65
adaptive design. For example, if a coastal road used for evacuation could be threatened in
the future by erosion, an alternative inland route or a redundant road could allow for
managed retreat of the coastal road without loss of function.

Survival of Protective Structures. Coastal structures can provide several levels of
protection. The most effective level of protection comes from structures that prevent
damage to inland communities and remain functional. A second level of protection comes
from structures that remain functional after a disaster. The structure may not provide
complete protection from an extreme event, but when the structure survived the event, it
can protect recovery efforts from future smaller events and help community rebuilt. The
structure may not fit with the future plans for the community, but could be repurposes or
removed after rebuilding has occurred. A lesser level of success comes from structures
that collapse or fail during the disaster, but provide significant protection prior to failure
(Ewing and Synolakis 2011). The Kamaishi breakwater is an example of such a structure.
The breakwater collapsed during the Tohoku tsunami; but reduced flooding from an
unprotected level of 13.8 meters to a measured level of 8 meters, and delayed the time of
wave landfall by several minutes (Takahashi et al. 2011).

Coastal protection is an important aspect of community resilience. Information on better
design methods can help improve structural protection. But, as seen from recent coastal
disasters, even well-designed structures are fallible and cannot be counted upon for
protection from all events. Structures can be overtopped, can be breached, can be
undermined or scoured, and can collapse. Some structures can be upgraded to address
new design conditions, especially those structures with room to provide for an expanded
foundation. New structures can be designed to accommodate adaptation to future, more
demanding conditions. It is important that realistic protective levels be assumed for the
risk and vulnerability assessments discussed in Chapter Three. Due to different design
conditions, not all structures provide the same level of protection. Even structures with
the same design conditions may differ in protection effectiveness over time, due to
differences in local hazards, local geologic conditions, on-going maintenance, or
structural deterioration through poor maintenance. Knowing how to provide proper
protection is important, but there can be gaps between good knowledge and good
execution. As a result, some development and infrastructure may be of such importance
to a community that it will require redundancy in function, or plans for eventual removal
from high-risk coastal locations. As will be discussed in later sections, community
resilience includes recognition of the utility of all protective options and steps to match
protective efforts with functional importance, through changes to both the protection and
the functions.
Page 66
Chapter Five
Community Resilience and
Coastal Protection

Armoring shorelines remains the strategy of choice against rising seas in many
parts of the world. Twenty-first century technology allows us to fence off the
land at vast expense on a scale unimaginable even a century ago. The costs are
gargantuan beyond the purses of many endangered lands – and there is no
guarantee that armoring will ultimately work.
Brian Fagan, The Attacking Sea

5.0 Introduction
This chapter reviews many of the definitions of resilience, socio-economic and
environmental characteristics of resilience and resilience of communities. It discusses
resilience with respect to climate change and adaptation and opportunities to manage for
resilience in coastal communities. Communities often have little understanding of how to
modify or improve upon existing resilience. This chapter characterizes the resilience of
many of the more commonly used elements of community protection, including natural
protective features, engineered structures, building-scale protection, and land use options.
Community resilience results from the combined effects of these multiple aspects of
protection and community function.

There are two separate aspects of resilience – the ability to cope with and survive various
hazardous events that tend to damage portions a community, and the ability to return to a
state of normalcy following a damaging event. The first part of resilience can often be
considered to be the lack of vulnerabilities. Evaluations of vulnerability and resilience
depend upon local hazard conditions and community development patterns. As noted in
Chapter Four, lessons from past disasters can provide guidance for damaged communities
in their rebuilding or for other communities as they assess their vulnerabilities to coastal
hazards. Furthermore, the value of shore protection during a disaster is integrally linked
to the development that is being protected. However, the values of protection during
recovery and routine conditions are linked to the protection characteristics. These two
phases of resilience are both covered in this chapter.

5.1 Definitions of Resilience
Resilience is a term that is used in many different situations and contexts. For most
situations, resilience has been generally considered to be a positive characteristic by
many different disciplines. In general usage, resilience represents the ability of an object
“to recoil or spring back into shape after bending, stretching, or being compressed; … (of
Page 67
a person), to withstand or recover quickly from difficult conditions.”
27
In the field of
materials engineering, resilience is a material property and there is no ascribed beneficial
or detrimental quality to the property. According to the American Society of Metals,
ASM International (Davis, ed. 2006), resilience is the “ability of a material to absorb
energy when it is deformed elastically, and to return it when unloaded…... usually
measured by the modulus of resilience”. The modulus of resilience (U
R
) is defined as: U
R

= 0.5s
0
e
0
(or s
0
2
/2E), where s
0
is yield stress, e
0
is strain and E is Young’s Modulus
or modulus of elasticity.

Most definitions of resilience are not as quantitative as in material science. Computer
networking ascribes beneficial values to resilience, and considers resilience to be
synonymous with system fault tolerance and the ability to continue to “operate correctly
even though one or more of its components are malfunctioning” (NTIA and Federal
Telecommunication Standards Committee 1996). In Resilience Engineering, (Hollnagel
et al. 2006, p. 22) define resilience as “the ability to recognize and adapt to handle
unanticipated perturbations that call into question the model of competence, and demand
a shift of processes, strategies and coordination.” Each of these definitions has a common
theme of performance during and after some stressor or perturbation and they focus on
various aspects of resilience that are important to specific groups or disciplines.

The general idea of resilience as a system property began to emerge in the 1970s, through
work by C.S. Holling and a group of natural resource scientists and ecosystem managers
who established a Resilience Alliance. The first major discussion of ecosystem resilience
was presented by S.C. Holling (1973) in ‘Resilience and Stability of Ecological Systems’.
In this work, Holling compares management for stability with management for resilience;
in management for stability, systems would return to an established equilibrium state and
stability could be assessed by the speed of recovery with few fluctuations from the
equilibrium conditions (Holling 1973, pg. 17). In contrast, Holling characterized system
resilience through the continuity of relationships within the system during changing
conditions” (Holling 1973, pg. 17)

As a system property, management for resilience would focus on persistence or the
probability of extinction, and management for stable systems would focus on fluctuations
around some identified equilibrium states (Holling 1973). Each system has advantages.
Ecosystems that exist in regions with extreme conditions -- areas with large changes in
temperature, water availability, or salinity – tend to exhibit large population fluctuations
(low stability), but have a high capacity to absorb these extremes and continue to persist
(high resilience). In regions with more moderate conditions, populations are more
constant, or have high stability, but may have low resilience to occasional extreme
conditions (Holling 1973).

In a resource management context, such as agriculture, aquaculture or silvaculture,
stability focuses on equilibrium conditions, the maintenance of a predictable world, and
extraction or harvesting of resources at a rather constant rate. According to Holling,

27
From Oxford English Dictionary, www.askOxford.com; last consulted 23 April 2009
Page 68
management for resilience would keep options open and focus on species variety to
account for unexpected events. Also according to Holling, a resilience framework will
promote systems with the capacity to absorb and accommodate changing conditions
(Holling 1973, pg 21). The ability of resilient systems to accommodate uncertainty has
made resilience a popular concept for several different disciplines, from its start in
ecological management to the study of social systems, disaster planning and engineering.

The work by C.S. Holling and others has established resilience as a component of
ecosystem or environmental management. Ecosystem resilience often includes the
concept of self-organization and self-correction (Walker and Salt 2006, pg. 1). The
Resilience Alliance (RA) initially covered resilience as a function of natural systems, and
later expanded this to address resilience of social systems as part of the environment. In
this case, the Resilience Alliance
28
ascribes to social-ecological systems:

the added capacity of humans to anticipate and plan for the
future.…‘Resilience’ as applied to ecosystems, or to integrated systems of
people and the natural environment, has three defining characteristics:
• The amount of change the system can undergo and still retain the same
controls on function and structure
• The degree to which the system is capable of self-organization
• The ability to build and increase the capacity for learning and
adaptation.

5.2 Resilient Cities and Communities
Ecosystem resilience is rarely a single, one-time characteristic; resilience is a group or
combination of on-going traits and qualities that reduce vulnerability (Ewing and
Synolakis 2011). Resilience of complex communities, like cities or metropolitan areas
has some of the same characteristics as resilience of an ecosystem – the ability to
withstand and recover quickly from system shocks. Resilience has been a strong focus of
city and urban planners in response to growing costs of urban disasters. Resilient cities
“combine seemingly opposite characteristics, including redundancy and efficiency,
diversity and interdependence, strength and flexibility, autonomy and collaboration, and
planning and adaptability” (Godschalk 2003, pg. 141). A resilient city that can cope with
uncertainties is expected to fare better after a disaster than a city that is less flexible. But,
there is not a specific development pattern that establishes resilience; rather, resilience
results from creative options tailored to the unique characteristics of the community
(Godschalk 2003, pg. 138).

History is replete with non-resilient cities -- cities like Atlantis that vanished completely
due to an enormous surge of water that washed it away, or cities like Ephesus that had a
more gradual decline. Ephesus was established in the 10
th
century BC, on the banks of
the Cayster River, close to where the River then emptied into the Aegean Sea (Hawkins
2009). Silt from the river built up as a large delta, shoaling the original harbor and in 281

28
From: www.resalliance.org/576.php
Page 69
BC, a new Ephesus was built about 2.5 km from the original location to re-establish
water access (Strabo 1923-19-32).

Located in an active earthquake zone, the city experienced several cycles of damage,
followed by rebuilding and recovery. However, the delta continued to expand into the
Aegean and the harbor gradually became less and less sustainable. The city lost its
position as a center of trade and commerce, the harbor was abandoned, and by about
1000 AD, Ephesus had gone from being a major commercial center to only a small
village; by 1300 AD the city of Ephesus was completely abandoned
29
. The now
abandoned city and harbor are about 5 km from Aegean. And, the fate of Ephesus was
repeated throughout the Mediterranean. The Athenian port of Piraeus began as an island
and was linked to the mainland by accretion of sediment, later stabilized by long walls
(Fagan 2013).

Just as Ephesus was abandoned due to receding water, other settlements have been
abandoned due to encroaching water. However, due to the slowing of sea level rise that
started about 5,000 to 6,000 years ago (Figure 3-1), coastal communities in particular
have come to expect a rather static coastline, interspersed with periods of change that are
far smaller than what likely occurred previously.

In Resilient Cities, Vale and Campanella (2005) hypothesize that few modern cities have
disappeared following a disaster, and the very act of rebuilding can be considered an
indicator of a city’s resilience
30
. This indicator of resilience does not consider the time
for rebuilding, social and economic costs for rebuilding, or the time the rebuilt
community can survive without another disaster. When disasters to coastal communities
continue to result in fatalities, ecological damage, and enormous economic losses,
rebuilding may not be sufficient for resilience. Rather than considering construction to be
the equivalent of resilience, resilient communities should be considered those that
minimize or avoid loss of functionality during a coastal event and recover functionally
quickly after the event (Ewing and Synolakis 2012).

Over the past two centuries, most cities that have been destroyed by natural or human
events have been rebuilt (Vale and Campanella 2005). Building and rebuilding are
obvious parts of urban resilience, but human, social, cultural and political elements of the
city are also part of the resilience, and in some cases, they are more important. Urban
rebuilding can provide assurance about the future, as well as employment for people
affected by the disaster (Vale and Campanella 2005); however, disasters damage more

29
Tore Kjeilen, http://lexicorient.com/e.o/ephesus.htm, last visited 11January2014.

30
Vale and Campanella provide a more thorough examination of the elements of a city that
provide resilience, and present a more detailed picture of resilience that just rebuilding. However
there is a tendency following a disaster to focus on getting things back to the way they were with
little thought about whether there are better options for community recovery. Pre-disaster
property lines, utility easements, public rights-of-way and the need to reconnect damaged systems
with undamaged segments outside the damaged area also perpetuate rebuilding plans that follow
the pattern and footprint of the previous development.
Page 70
than bricks-and-mortar and often present challenges for government and community
leaders that go beyond reconstructing community protection.

Traditional disaster preparedness has focused on increasing the strength or resistance of
engineered protection structured. Godschalk (2003) and others have observed that cities
that emphasize only physical resistance tend to be brittle and fragile, whereas cities that
focus on resilience tend to be strong and flexible. Resilience is often used in conjunction
with other terms such as sustainability or adaptive capacity. These three concepts often
overlap, and the boundaries between resilience, sustainability, and adaptation are rather
blurred. For example, Folke et al. (2002a, p. 7)

define adaptive capacity as “the ability of
a social-ecological system to cope with novel situations without losing options for the
future, and resilience is key to enhancing adaptive capacity”. In a second paper on
resilience and sustainable development, Folke et al. (2002b, p. 440)

posit that,
“managing for resilience enhances the likelihood of sustaining development in a
changing world where surprise is likely.”

Due to these flexible, cope-with-surprise aspects, resilience, has become a regular
component of disaster management and disaster planning. In the context of disaster
planning, resilience is consider to be a characteristic of the community that can be
enhanced prior to a hazardous event through proper planning, preparedness and
mitigation. In contrast to this broad characterization of resilience, Rose (2007) views
resilience as an economic characteristic that is only part of a post-disaster response. He
distinguishes between a community’s ability to cope with normal perturbations as being
“inherent resilience” and the responses made by a community to maintain function during
and after a crisis depend upon “adaptive resilience” which rely upon “ingenuity or extra
efforts” (Rose 2007). Yet, others relate resilience to post-disaster conditions and response
(Comfort 1994), rather than the hazard mitigation efforts that are pre-disaster activities to
reduce potential losses.

The National Oceanic and Atmospheric Administration (NOAA) developed a generic
resilience curve (Figure 5-1) that shows the basic elements of resilience in the context of
both pre- and post-disaster characteristics. This NOAA representation of resilience
shows some activity or service that is functioning normally until a disaster causes an
abrupt change in function. The disaster event is followed by an extended period of
diminished function, until a new normal service function is reached.

Page 71

Figure 5-1. Community Resilience and Functional Capacity
Source: NOAA & Mobile Bay Chamber of Commerce (2007 - 2008). Mobile Bay Region
Creating a Strategic Framework for Regional Growth and Resilience.

The NOAA resilience curve shows recovery relative to the level of function. If function
is considered too narrowly, recovery may return a system or community to a function that
is not the most appropriate for the future. For example, if a port’s function historically
has been to handle break-bulk cargo, but activities are shifting to containerized cargo,
defining the port function in terms of break-bulk capacity would limit the overall
recovery potential. A better measure of the port’s function might be transfer of cargo or a
container metric such as TEU’s (twenty-foot equivalent units, or the capacity of a normal,
20-foot long shipping container), or value of goods shipped. Many community functions
do not have a metric such as TEU or goods shipped, so there is no easily measured
baseline to use for either pre-event function or to determine when recovery is over
(Ewing and Synolakis 2012). In some cases, there may be no baseline and, as an
indication of flexibility, resilient systems may continue to fulfill their purpose or function
while continually accommodating and adapting to ever-changing circumstances (Zolli
and Healy 2012, pg. 13).

Investigations of several service losses, such as the power loss and recovery following the
tsunami in American Samoa (Figure 5-2) or the loss and repair of customer connections
following hurricane Sandy (Figure 5-3) confirm the overall validity of this generic curve
for isolated systems. However other examples demonstrate variations in this curve, with
added stressors occurring during the recovery phase or pre-conditioning prior to a disaster
that might augment or minimize functional decline during the event. For example, there
was a snowstorm several days after Hurricane Sandy that added to the service outages
within the PJM system (Figure 5-3), adding to the overall system outages, and extending
the time for the system to return to full function. New Orleans provides examples of the
pre-conditioning of a community function. Figures 2-1 and 2-2 show the population
trends for Orleans Parish and the cargo trends for the Port of New Orleans. Population
and port activity were declining prior to Hurricane Katrina, and the ‘return to normal’
reflects, for the time being, these pre-disaster trends.

Page 72

Figure 5-2. Generating Capacity in American Samoa following the 2009 Tsunami.
The main power station on the island of Tutuila was destroyed by flooding. Initially small diesel
generators, installed throughout the island provided replacement capacity. On December 1, 2009,
27 1-MW rental generators replaced the 56 small generators. In summer 2013, the power
company signed a contract for the construction of a new 25-MW generating station that will
replace the temporary generators.

Walker and Salt (2006) present the idea that some ecosystems may experience sufficient
degradation or alteration that they can shift to a very resilient, but undesirable state. The
anoxic and dead zones (Diaz and Rosenberg 2008) that are being observed in the ocean
could be examples of this type of undesirable resilience. Mayor Joe Riley of Charleston,
at the Solutions to Coastal Disasters 2002 conference, verbally offered his observations
that disasters can push a community in the direction it is already going. If a community is
in a vibrant period of revitalization, then the community will keep that going after the
disaster. But, if the community is in decline and services are not being maintained or
improved, then the disaster seems to accelerate the decline.

Despite the range of definitions of resilience, none, except the ecosystem presentation of
resilience, recognize that communities are dynamic systems that have some direction or
trend. Communities will always be in some phase of rebuilding, building removal,
recovery, or decline. Holling and Gunderson (2002) describe these ecological phases and
the flows between them as conservation, release, reorganization, and exploitation. If these
four phases are formulated for communities and centered on disasters, they may be
considered as pre-event, event, event response, and event recovery, or the actions that a
community can take immediately before a disaster, the actions and responses during the
event, the immediate responses after the event, and the actions taken during recovery, but
before the onset of the next event. These event cycles might not be of the same for each
community and each disaster. If a community is a risk from typhoons and tsunamis, as is
the case for many communities in Japan, the initial event might be a tsunami. Yet when
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,000
Generating Capacity (kW)
Date
American Samoa Electrical Generation (kW)
Page 73
resilience is considered within the context of multiple hazards, the tsunami recovery
might be cut short by pre-event actions for a typhoon. Another example is Typhoon
Haiyan in the Philippines, where a large earthquake occurred a month before the typhoon.

Figure 5-3. PJM’s Electrical Service following Hurricane Sandy.
The main drop in service on October 29, 2012, was the result of Hurricane Sandy. The small drop
in customer connections on October 9, 2012 occurred due to an early snowstorm that was not
related to Hurricane Sandy, but caused an additional drop in function.

This idea of trend or pre-conditioning needs to be part of resilience, where a return to pre-
disaster function should not be considered to be resilience if the pre-disaster function was
not sustainable or the pre-disaster community did not have capacity to recover from
routine events. In other situations, the immediate losses or the time for recovery may be
so large that a return to pre-disaster function may not be possible. As an example, in the
mid-1970s, the port of Kobe, Japan was the busiest shipping container port in the world
(based on TEUs or twenty-foot equivalent containers) and remained one of the top ten
container ports in the world until the 1995 Great Hanshin earthquake caused extensive
damage to the port and the surrounding community. Shippers quickly moved their routes
to other ports, and even though the Port of Kobe was brought back into service, it has not
returned to its former prominence. Despite annual growth in container traffic, Kobe
dropped from being one of the top ten busiest container ports in the world prior to the
earthquake to being the 29
th
busiest container port in 2002, 39
th
busiest by 2005, and to
45
th
place by 2010
31
, as shown in Figures 5-4 and 5-5. Clearly, disasters can result in
quantum shifts in community function, sometimes for the better and sometimes not.

31
American Association of Port Authorities: World Port Rankings; http://www.aapa-
ports.org/Industry/content.cfm?ItemNumber=900; last visited 12January 2014
52,000
53,000
54,000
55,000
56,000
57,000
58,000
59,000
60,000
61,000
10/15/2012
10/22/2012
10/29/2012
11/5/2012
11/12/2012
11/19/2012
11/26/2012
Customers with Service -
Thoushands
Date
Page 74
While resilience is often considered within the context of disasters, the manner in which a
community addresses disasters will influence the overall function of the community
during times of disaster as well as the periods between disasters. Also, disasters tend to
accelerate community activities, both declines and improvements. Post disaster recovery
occurs in a more rapid and different fashion that would occur with routine maintenance
and replacement (Olshansky et al. 2012). Olshansky et al. (2012) refer to this
acceleration as ‘time compression’. Such time compression can greatly reduce the time
to rebuild damaged infrastructure or other structures; however this period of rapid growth
may often be followed by a drop in the normal replacement rate since so much of the
infrastructure is new. This time compression can be seen in the rapid recovery of the
Ports of Kobe (Figure 5-5) and New Orleans (Figure 2-2). The focus on rebuilding and
recover can also provide an opportunity to improve on capital facilities, especially those
that may be nearing the end of their useful lives. However, the opportunity for
improvement and change may be short-lived as residents, businesses, industry, and the
community all compete for the same scarce resources, like skilled labor, financing,
building supplies, and equipment (Olshansky et al. 2012).

Figure 5-4. Port of Kobe Container Traffic
Note that the Great Hanshin Earthquake occurred in 1995.
Source: AAPA World Port Statistics

Borrowing from the various examinations of resilience, the key elements of a resilient
community are that it can:
• adapt to changing conditions without losing function (Godschalk 2003)
• recover from random, unexpected events, often in creative ways (Walker and Salt
2006)
• rely upon local, and regional resources for much of the recovery (Holling 1973),
and,
• use learned experience to reduce vulnerability and improve future conditions
(Mayor Riley).
0
50
100
150
200
250
300
1975 1980 1985 1990 1995 2000 2005 2010 2015
Container Traffic (10,000 TEUs)
Year
Port of Kobe Container Traffic
TEUs (10,000)
Page 75

Figure 5-5. Port of Kobe World Ranking in Cargo Traffic
Note that the Great Hanshin Earthquake occurred in 1995.
Source: AAPA World Port Statistics

Despite the range of definitions of resilience, none, except the ecosystem presentation of
resilience, recognize that communities are dynamic systems that have some direction or
trend. Communities will always be in some phase of rebuilding, building removal,
recovery, or decline. Holling and Gunderson (2002) describe these ecological phases and
the flows between them as conservation, release, reorganization, and exploitation. If these
four phases are formulated for communities and centered on disasters, they may be
considered as pre-event, event, event response, and event recovery, or the actions that a
community can take immediately before a disaster, the actions and responses during the
event, the immediate responses after the event, and the actions taken during recovery, but
before the onset of the next event. These event cycles might not be of the same for each
community and each disaster. If a community is a risk from typhoons and tsunamis, as is
the case for many communities in Japan, the initial event might be a tsunami. Yet when
resilience is considered within the context of multiple hazards, the tsunami recovery
might be cut short by pre-event actions for a typhoon. Another example is Typhoon
Haiyan in the Philippines, where a large earthquake occurred a month before the typhoon.

In the context of coastal disasters to the built environment, a resilient community can be
represented by the following characteristics:
• Survival of the people living in the community (measured as population that is not
vulnerable to hazard through exposure or sensitivity)
• Ability of people to remain in the community during the event or return quickly
(measured as a percentage of residential building stock that is not vulnerable to
coastal events; cost of lost building stock; time to restore building stock)
0
20
40
60
80
100
1975 1980 1985 1990 1995 2000 2005 2010 2015
Ranking -- 100 is highest rank
Year
Port of Kobe World Ranking
Before and after 1995 Earthquake
Page 76
• Infrastructure remains functional or becomes functional soon after the event
(measured as percentage of each infrastructure system that is not vulnerable or
dependent on other vulnerable infrastructure; time to restore to full function)
• Maintenance or enhancement of community amenity values such as ecosystem
areas and recreational space (measured as the percentage of community beach and
land area available for open space and habitat)

5.3 Climate Change, Adaptation, and Resilience
Climate change has been one of the rallying points or stimuli for discussions about
resilience. The Rockefeller Foundation has begun a climate initiative for resilience,
focusing on ‘Five Dimensions of Resilience’ – Information, Infrastructure, Insurance,
Institutional Capacity and Integrated Systems (Rodin 2008). The Stern Review (2007)
discusses ‘climate resilience’ and notes that efforts to develop climate resilience extend to
decisions on technology transfer, human capital, infrastructure, social networks and
natural systems.

Coastal change from climate change is mostly tied to rising sea level, changes in fluvial
processes, and changes to meteorological events such as El Niños, hurricanes, and
tropical cyclones (for example, Dettinger 2011; Cai et al. 2014; Johnson 2014; Emmanuel
2007; Vecchi and Soden 2007; Knutson et al. 2010). Flooding is expected to cause the bulk of
the overall damage and result in the largest financial losses. Taking only direct losses into
account, flooding in coastal cities worldwide annually damages assets valued at $6 billion
US (Hallegatte et al. 2013). Damage costs from large events, including direct and indirect
losses, far exceed this annual direct loss average -- $125 billion US for damages from
Hurricane Katrina and US$70 billion for damages from Hurricane Sandy. However, such
extreme losses may become more routine with rising sea level and increased coastal
development, possibly exceeding $1 trillion US by 2050 (Hallegatte et al. 2013).
32
When
such losses are compared with the costs of adaptation or flood avoidance, protecting
coasts around the world with dikes might be several orders of magnitude less than the
damages, costing only $12 to $71 billion US annually by 2100, depending upon the
community assets in the coastal area and the amount of sea level rise (Hinkel et al. 2013).
These estimates for diking costs do not cover the social and environmental costs from
these flood control structures, and, in many situations, more nature focused responses
may be as protective with fewer accompanying impacts.

32
This projection is presented as an annual loss estimate with about half the losses from socio-
economic changes only. Physical damages also assume that community rebuilding occurs without
any improvements in flood protection so that the same community could be damaged repeatedly.
Details on assumptions from paper and comments provided by the author to Brian Kahn, as
reported in Kahn, B. 2013. “Floods may Cost Coastal Cities $60 Billion a Year by 2050” Climate
Central, www.climatecentral.org/news/, (last visited 11Feb2014).
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5.4 Managing for Resilience in Coastal Communities
The 21
st
century has already experienced several coastal disasters that had global
repercussions. The social, ecological and economic tolls exacted by these recent disasters,
combined with concerns about sea level rise and climate change, highlight the importance
of coastal resilience. Following the 2004 tsunami that devastated communities throughout
the Indian Ocean, the US Indian Ocean Tsunami Warning System Program (US
IOTWSP) highlighted eight components of community resilience -- risk knowledge, land
use and structural design, warning and evacuation, emergency response, coastal resource
management, society and economy, disaster recovery and governance (Courtney et al.
2008). Five aspects of resilience for tsunamis were identified (Jonientz-Trisler et al.
2005, pg. 123) as being equally useful for resilience to all coastal hazards:

• Understanding the nature of the hazard,
• Having the tools to mitigate the risk,
• Disseminating information about the hazard,
• Exchanging information with other at-risk areas, and
• Incorporating disaster concerns into normal planning activities.

With respect to coastal communities in particular, the US IOTWSP identified resilience
as the intersection of three components -- disaster management, coastal management, and
community development. This intersection of efforts is an important aspect of coastal
resilience. Disasters, if viewed as opportunities, can lead to a reexamination all the issues
related to hazard protection, disaster response, coastal management, and community
development.

Disaster management, the first component of US IOTWSP resilience, mainly considers
damage-causing events, emergency situations and recovery. The Red Cross and Red
Crescent Societies define disaster management as, “the organization and management of
resources and responsibilities for dealing with all humanitarian aspects of emergencies, in
particular preparedness, response and recovery in order to lessen the impact of
disasters.”
33
Disaster resilience describes limiting the losses that a community will face
both from the initial disaster, as well as during the post-disaster recovery. The aspects of
resilience outlined by Jonientz-Trisler et al. (2005) focus primarily upon disaster
management, including examination of the types of hazards to which a community may
be exposed, the assets that are at-risk from these hazards, the protective features of the
community, and the damages due to various levels of event.

A more resilient community should experience less immediate losses and more rapid and
better quality recovery than a less resilient community. Resilience depends on many
aspects of community, such as governance, risk knowledge, warning and evacuation,
emergency response, disaster recovery, society and technology, and land use and
structural design. For coastal communities, coastal zone management and coastal

33
International Federation of Red Cross and Red Crescent Societies,
http://www.ifrc.org/en/what-we-do/disaster-management/about-disaster-management/, (last
visited 1Feb2014).
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protection, both natural and built, are part of that resilience. Coastal management, the
second component of US IOTWSP resilience, in contrast to disaster management, takes a
broader and more comprehensive approach to resilience by including coastal resources.
As noted by NOAA’s Office of Ocean and Coastal Resource Management
34
, coastal
management often balances the “competing and occasionally conflicting demands of
coastal resource use, economic development, and conservation.” Some of the key
elements of coastal management identified by NOAA’s Office of Ocean and Coastal
Resource Mangement include:
• Protecting natural resources;
• Managing development in high hazard areas;
• Giving development priority to coastal-dependent uses;
• Providing public access for recreation; and
• Coordinating state and federal actions.

Community development, the final aspect of coastal resilience as identified by the US
IOTWSP, is a broad term that covers concerns for an involved citizenry, incorporation of
diverse interests and cultures, enhancing the voice and leadership capacity of community
members, and supporting the overall well-being of the community. Social justice issues,
affordable housing, job creation and anti-poverty programs are often identified as
community development activities. In the US, many community development activities
are funded through the Community Development Block Grant program. This funding can
cover the construction of and improvements to public infrastructure. In 2012,
expenditures for public improvements, including infrastructure and utilities, accounted
for approximately one-third of all community development funds
35
. So, the provision of
utilities and basic services also comes under the umbrella of resilience of a coastal
community.

The process for managing community resilience starts with identification of hazards.
Some hazards may only be identifiable through their presence or absence, such a
liquefiable soils or landslides. Other hazards may have a probabilistic impact level or
frequency of occurrence, such as a 100-year flood zone or an average annual bluff retreat
rate. The probability of an event will often be part of the examination of resilience;
however, probability or low probability should not be used to exclude hazards from
consideration, since a major advantage of resilient systems over resistant systems is their
ability to deal with unexpected events or, as defined by Hollnagel et al. (2006) in
Resilience Engineering, ‘to handle unanticipated perturbations’. Thus, low but probability
but high impact events need to be part of the analysis of resilience.

The second half of managing community resilience is related to the assets (in this
situation, infrastructure and life lines, as identified in Chapter Two) that are vulnerable to
the hazards due to exposure or sensitivity. Exposure normally relates to the location of an

34
NOAA’s Office of Ocean and Coastal Resource Management,
http://coastalmanagement.noaa.gov/, (last visited 1Feb2014).
35
Based on the 2012 National Expenditures for Community Block Grants,
http://portal.hud.gov/hudportal/HUD?src=/program_offices/comm_planning/communitydevelop
ment/budget/disbursementreports, (last visited 1Feb2014).
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asset, and sensitivity is a characteristic of the asset that indicates the likelihood that
damage or loss might occur if the asset is exposed to the hazard. For example, beaches
are regularly exposed to flooding, but are only sensitive to flooding, if there the currents
and wave energy are sufficient to cause large amounts of sediment transport. Adaptive
capacity is another aspect of vulnerability. For example, a generator may be exposed to
and sensitive to flooding, but a flood-proof casing may allow the motor to adapt to flood
conditions. Hazard resilience often addresses opportunities to reduce exposure to hazards,
reduce sensitivity to hazards, or increase adaptive capacity.

Community resilience is a balance between the amount of coastal hazard protection that
is available and the amount and significance of the community assets that are exposed to
and sensitive to coastal hazards. Community disasters occur when the hazards exceed the
level of protection and significant assets and resources are lost or destroyed. At one
extreme of resilience, there could be a coastal community that has all critical
development out of the coastal hazard zone. This provides resilience from coastal
hazards, but it comes at a cost. It would be likely that many of the assets that make
coastal communities so attractive would not been used, for example, not taking advantage
of harbor areas for transportation and commerce or accessing coastal waters for fish,
shellfish, kelp, or aquaculture. At the other extreme, a community could cluster its major
resources along the coast and construct multiple protective features to keep the assets
from harm. This type of resilience could damage or destroy the natural coastal resources,
sometimes with little consideration for the many community benefits from natural
systems. While engineered protection often has an ascribed level of protection that cannot
be provided for many natural systems, there remains a concern that the engineered
protection may fail due to age, poor maintenance, error, changes in hazard intensity,
extreme events, or some unanticipated event.

Cultural, social and technological changes may help increase resilience to coastal
disasters by helping move more facilities away from the coast. For example, an increased
use of renewable energy and less reliance on once-through cooling could reduce the
concentration of electric power generation along the coast. Wastewater treatment is
another community service that now concentrates along the coast to take advantage of
gravity flow to move sewage and wastewater from the source to the treatment location.
Future dedications of coastal land for wastewater treatment may decrease through a
combination of technological changes (often called green infrastructure) and
conservation, such as efforts to increase divert storm water from treatment through
increased ground water recharge, low-impact development (LID) or to reduce water use
and to treat more water in small batch plants.

In general, coastal community resilience will increase with either increased protection of
community assets from coastal hazards or reduced exposure and sensitivity of community
assets to coastal hazards. There is often a correlation between at-risk assets and
protection, such that, as significant community assets increase in coastal hazard zones,
the need for protection will increase. Also, as the provision of protection increases,
acceptance of putting more and more significant community assets in coastal hazard
zones increases. Using benefit cost analysis, the costs for coastal protection can be
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justified by increasing the benefits (protection of more and more community assets). So,
even though a secondary road may not warrant protection, if it is upgraded to a major
highway and rail corridor, the potential losses could increase such that future protection
will be cost effective. Alternatively, if a major transportation corridor is vulnerable to
coastal hazards, the resilience of the community transportation system could increase by
relocating the major facilities to a safer location and converting the vulnerable corridor to
one that provides more local service.

As noted in Chapter Two, communities place a high level of importance on physical
resilience (CERES et al. 2013). In coastal communities, physical resilience is strongly
tied to the long-term functionality and recovery of natural and built protection. The
resilience of coastal community protection depends upon interactions of these various
elements that make up the protection system. Quite often though, a community’s overall
coastal protection system is an amalgam of disparate features constructed at different
times, for a range of purposes, and different design levels. The communities that are
being protected have likely grown several-fold in land area, population and resources
since the time the protective features were installed. The structures that provide
community protection often have not kept pace with the community’s development. The
natural and constructed protective structures are often owned, managed, and maintained
by different parties. The original purpose for the protection may no longer exist, and the
structures may have been modified over time, thus changing the design conditions. These
structures are now often expected to work as a coherent system. Some structures may
overlap and augment the overall protective function of the system, while others may
diminish the protective function of other parts of the system or leave some areas under
protected. New Orleans was an example of these many problems with coastal protection
that became evident in the aftermath of Hurricane Katrina (IPET 2006; ASCE2007).

5.5 Elements of Community Resilience
Resilience is an on-going community condition, and it occurs at many temporal and
spatial scales. The community elements may provide resilience that is very important at
one scale and that is rather ineffective at other scales. For example, the geotube-dune
structures in Galveston protected the communities from small storm events and from
annual-level floods, and from annual over-wash that might have closed the main road
(Ewing et al. 2009). However, these geotube-dune structures were of limited benefit from
the large waves that accompanied Hurricane Ike.

All communities have some level of resilience and some existing resilience elements.
Therefore, any analysis of resilience must take into account these existing elements and
the condition they are in. Generally, the overall resilience of a community results from
multiple elements – some natural coastal assets, some designed specifically for
protection, and others that have many purposes besides hazard resilience. Some resilience
elements will reduce the initial damage from an event, other elements might improve
recovery time, and others might help reduce damage levels from future events and
improve resilience over time. Resilience elements, as identified in Ewing and Synolakis
(2012) can include:
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• Natural buffers and protective features, such as beaches, dunes, bluffs, reefs,
or wetlands,
• Traditional engineering approaches such as seawalls, revetments, breakwaters,
and levees,
• Design efforts such as building elevation or fortification, and building codes,
• Early warning and evacuation to remove people and key community elements
from harm’s way once a coastal hazard is imminent,
• Land use efforts that locate key aspects of the community function in areas
that are not subject to coastal hazards, or
• Some combination of all of these.

Community Resilience from Natural Features. Natural features such as beaches,
wetlands and reefs have many values in addition to the protection that they provide to
inland regions. They protect water quality, promote fisheries resources, support vital
ecosystems, provide recreation areas, and improve the overall quality of life for nearby
communities. Natural features also contribute to overall community resilience during
event recovery and on-going activities by providing recreational opportunities, open
space, protection from non-disaster events, and overall community well-being.

Only 25 to 30% of the coasts consist of beaches (based on coastal classifications of The
Americas, Dolan et al. 1972) yet, most people think of beaches when they think about the
coast. In those coastal communities that do have beaches, these areas are multi-functional
ecosystems, providing habitat for coastal species, providing social and recreational
amenities for residents and tourists, and providing protection of inland development
during storm events. Beaches are quite dynamic systems, being reshaped by wind and
wave energy and changing in width as sand moves into or away from the beach areas.
Communities can modify beach areas by removing sand (often called sand mining),
placing sand on the beach (termed beach nourishment), or blocking the alongshore or
cross-shore movement of sand (called sand retention). Often these actions are intentional,
as the long-term consequences of interfering with the volume of sand on beaches have
only recently been realized.

Many beach areas are no longer wide enough or have sufficient sediment to provide
storm protection. As a result, many shore protection efforts have focused on beach
enhancement or restoration, ranging from efforts to restore natural supplies of sediment
to the coast, to active placement of sand on the beach through beach nourishment. Some
options for beach enhancement can include removal of dams, by-passing sediment around
dams to increase fluvial sediment supplies, using sand dredged from harbors and
navigation channels for beach nourishment, conveying sand past submarine canyons so it
is not lost to an offshore sink, use sand from reservoirs and debris basins, taking sand
from offshore deposits, or even using crushed glass for beach material.

The second aspect of beach nourishment is ways that keep sand on the beach, either sand
that is there through natural processes or sand that has been added to the system through
beach nourishment or enhancement. Retention options can include back-passing of sand
to keep it within the same area for a longer period of time; putting it into berms so it will
Page 82
remain as protection for the storm season; using shore normal structures like groins,
jetties or artificial headlands to retain sand on the upcoast beach; using shore parallel
structures like perched beaches and breakwaters to reduce wave energy; providing a
protected area for beach build-up, offshore structures like deltas for shoreline accretion;
or using beach dewatering to hold and accrete sand in specific locations. These options
are discussed further in Chapter Six and in Tables A-1 through A-5.

Beach systems as shore protection have received a large amount of attention. Beach
restoration is used in many areas for storm reduction; for example, beach restoration was
the first community-scale protection efforts along the New Jersey coast following
Hurricane Sandy. But, many other coastal ecosystems are important for coastal
community resilience. These systems, such as wetlands, marshes, mangroves, grasses,
and reefs are valued for their ecosystem function; yet, they too can offer important shore
protection value. Too often the protective value of these ecosystems is only understood
after their removal, such as when a navigation channel is cut through a reef, when
marshes are drained to create fastland, when a deep channel is cut through wetlands, or
when mangroves are replaced with aquaculture structures. The wave energy dissipation,
and protection from flood and erosion values from natural systems are often not
appreciated until these natural features are modified or removed,
Unlike engineered structures, or even beach nourishment, the protection benefits from
coastal ecosystems are difficult to quantify. The protection value of a levee can be
reduced to comparison between levee height and water level; but there are no simple
ecosystem metrics that can quantify their protective value. Coastal ecosystems are
complex three-dimensional structures that interact in multiple ways with coastal waves
and wave energy. These systems have elevated bedforms, either through the reef
materials or by trapping sediment and organic matter within their root structure. The
elevated bedform will reduce wave energy and wave heights, with the reduction in energy
and wave height being roughly proportional to increased bedform elevation and increased
projection of the wave across the structure. Plant structure will also dissipate wave
energy, with increased density and extent of vegetative cover causing greater dissipation.
The effects on waves also depend on the wave conditions; shorter period waves are more
rapidly dissipated than longer period waves. These factors make it difficult to isolate a
few identifiable characteristics that can be correlated directly to protection value.
Some rules of thumb or ratios have been developed for wave reduction. One such “rule”
is that runup across a beach will be reduced by 1 foot for every 25 feet of beach that is
crossed. However, as stated in the Coastal Engineering Manual (Section D 4.5-32), “in
most situations, the amount of dissipation is small when compared to the effort required
to analyze the dissipation processes. In addition, the risk of overestimating wave
dissipation with available tools, resulting in an underestimation of flood risk, can be
significant.”

An article in Physics Today by Resio and Westerlink (2009) also debunks
the use of rules of thumb for surge dissipation, noting, “empirical rules of thumb based
on observations alone may be of dubious value. Along the US Gulf Coast, observations
have suggested that each 14.5 km of wetlands leads to a 1-m decrease in the maximum
surge level. If true, that is an extremely useful piece of information. The estimate could
be dangerous, however, if it is false and used to estimate risk reductions in coastal areas
Page 83
behind wetlands” (Resio and Westerlink 2009).

Unfortunately, wave-ecosystem dynamics
are difficult to model and some estimates and rules of thumb may be all that is available
until basic understanding and modeling improves.

Coastal ecologists separate coastal habitats into many different types – tropical versus
mid-latitude, saline versus brackish water, soft versus hard corals. These distinctions are
quite important when describing ecosystem function. However, there is not enough
known about the protective values of each different system to split out the protective
values for each separate habitat type. For purposes of resilience and protection, these
habitats have been lumped into major groups -- wetlands, marshes and mangroves, dunes,
reefs, open space, and living shorelines. These options are discussed further in Chapter 6
and in Tables A-1 through A-5.

Resilience from Traditional Engineered Structures. Engineered structures are the most
easily identified elements of resilience and shore protection. Densely developed coastal
communities and urban centers often rely upon some forms of engineered protection for
key infrastructure and utilities, or as part of port development. The general options for
engineered shore protection are levees, horizontal levees, fixed and dynamic revetments,
walls, sand bag structures, and surge barriers. These options are discussed further in
Chapter Six and in Tables A1 through A-5.

The protective values from traditional engineered structures come from their physical
resistance to incoming wave energy or water levels. Unlike natural systems, most
constructed structures have little inherent value beyond the assets which they were built
to protect. There are, however, some exceptions; breakwaters provide safe navigation
anchorage in addition to storm protection, jetties support routine navigation activities,
and levees can support elevated roadways, bike paths, or hiking trails.

Protection provided by engineering structures will depend primarily upon the initial
design conditions, and the maintenance they receive so that they can continue to function
at their design level. Structures do not maintain the same level of protection over time
due to changes to the hazards and changes to the structure itself. For example, stones or
armor units may move or become dislodged from the main revetment or breakwater
structure. Even if there is movement of only a few stones or armor units, movement can
reduce the three-point contacts within the structure and reduce its overall stability.
Concrete units may suffer from spalling or cracking following repeated exposure to wave
attack and salt spray, causing connections and joints to weaken. As a result, the stability
and protective level of most structures will diminish with time, if they are not inspected
and maintained (Ewing and Synolakis 2012).

Even without consideration of deterioration and poor maintenance, the protection level
provided by structures varies greatly. As noted by Ewing and Synolakis (2012), in the
United States, many structures use a 100-year design storm condition. The 100-year
design level also means that, for most structures, extreme events are anything with less
than a 1% probability of annual occurrence. However, for some hazards the 100-year
event may not be near the upper range of observed values for the hazard. As shown in
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Figures 5-6 and 5-7, the 100-year return period may approach the high end of the hazard
threat for some situations, yet be far from the high end for other events. Figures 5-6
shows only the 100-year representation of a hazard, while Figure 5-7 shows the 1,000-
year representation of the event, with the same conditions through the 1% annual
probability of occurrence. Event A represents events such as wind wave heights that will
be limited by water depth, or generation conditions. Event B represents events such as
storm flooding or storms combined with high tides; while Event C represents events such
as tsunamis, hurricanes or some combination of high local waves, high tides, and a
tropical cyclone or hurricane. If designs only consider the 100-year event, some extreme
“tails” or outlier conditions can be omitted from the design considerations.

Figures 5-6 and 5-7. Hypothetical events with 100-year and 1,000-year return periods.

Also, actual protection from events will decrease over time if the structure deteriorates or
if the event frequency worsens. Over time, a 1 in 100 year event could become a 1 in 90
year or 1 in 75 year event. Sea level rise and land subsidence are other factors that can
increase event frequency. A flood occurrence study for San Francisco Bay found that
flooding associated with what is now considered to be the 100-year flood will become a
10-year event or even an annual event with a rise in sea level of 1 to 1.4 meters (Knowles
2010). This rise in water level was assumed to result from rising water levels, but could
just as easily result from subsidence during a seismic event. During the Tohoku
earthquake the coastal city of Onagawa experienced close to 1.2 meters of subsidence
(ASCE-COPRI-PARI 2013). In addition to sea level rise and land subsidence, shifting
storm patterns is another reason for changing return periods. For locations with little
historical data on hazard event, improved event histories may result in changes to return
period calculations (Ewing and Synolakis 2012).

Project design conditions can also shift due to changes to community character or
expectations. As noted by Kamphuis (2010) land development patterns can push high-
value resources into high-risk areas where the existing protection does not match the new
development conditions. This has been seen in areas such as the Sacramento-San Joaquin
0 50 100
Recurrence, in years
Hypothetical Events
to 100 years
Event A
Event B
Event C
0 500 1000
Recurrence, in years
Hypothetical Events
to 1,000 years
Event A
Event B
Event C
Page 85
delta in San Francisco Bay and other parts of the world, where haphazardly built levees
or dikes often were adequate protection for low-lying agricultural lands, but are not
adequate for residential land uses. While the land was in agricultural use, overtopping or
breaches would have resulted in the loss of crops, and farmers would have had easy
access to the levees to do repairs, or to add more material to the embankments. Also,
levee expansion could have encroached into a small portion of the farmable land.

However, with conversion of this same area to homes and commercial buildings, the
losses from a breach grow astronomically; access for repairs or routine maintenance
would be hindered by the development; and landward expansion of the levee would
conflict with roadways, utility corridors, or private, developed land. A 1990 IPCC study
(Dronkers et al. 1990) found that these constraints on urban area levee upgrades resulted in
costs that were 20 times more than similar upgrades in rural areas. When protected
agricultural land is converted to residential or commercial development, it creates a
situation where the protection is no longer suited to the newer land uses and community
expectations, and efforts to maintain or upgrade the protection can be very costly.

In addition to changing project designs, design conditions can also change over time.
Urban flooding frequency has increased due to greater urbanization and expansion of
impermeable surfaces, often requiring a reassessment of flooding risk (Wheater 2006).
Over the past 10 to 15 years, it seems that the consequences of coastal events have been
worsening and that globally, extreme coastal events are becoming an almost annual
occurrence somewhere along the coast. Due to early warning systems, improved weather
tracking, and better building construction, fatalities associated with coastal events are
decreasing.

Despite better building practices, property losses continue or are growing (Pielke, Jr. and
Sarewitz 2005). Recovery efforts can take months or years and can monopolize large
amounts of financial capital and resources, reducing resources for other communities or
other important efforts. Efforts to recover from the last disaster can distract from the
routine repairs and maintenance in other locations, potentially laying the foundation for
another disaster. As identified by Borrero et al. (2005), in a study of possible tsunami
damages to the Ports of Los Angeles and Long Beach, CA, the indirect losses from
business interruptions and resources diverted to recovery can often exceed the direct
losses.

People often find comfort in recovery being a return to what used to be. However, in
shore protection especially, this can cause a return to vulnerability. Resilience recovery
should attempt to build what will be more effective for future conditions. As an example,
communities along the Galveston coast that were not protected by the Galveston Seawall
were relying upon coastal dunes with a geo-tube core for their primary shore protection.
Houses inland of the dunes were elevated for added flood protection; however, the dunes
were intended to protect the roadway and utilities. The dune systems provided only
marginal protection during Hurricane Ike (Ewing et al. 2009; Watson 2009), and many of
the geotube cores were damaged. Not only did these structures not provide protection
during the hurricane, they were too damaged to provide protection during the recovery
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efforts. In most locations, these geotubes became beach debris that needed to be removed
as part of the recovery process. These structures were not rebuilt; instead, the Texas Land
Office and local governments diverted resources to take care of these structures and by
2009, all the geotubes had been removed from the beach (Ewing and Synolakis 2012).
The low-lying communities on the west Texas coast are examining a number of options
for reducing hazard vulnerability, including building elevation, relocation, and removal.
Beach and dune restoration is part of the community resilience, but the communities are
now aware that the limitations of the previous geotube dune systems do not make them
suitable systems for extreme storm protection.

One of the lessons from Hurricane Katrina concerned the limitations of New Orleans’
previous storm protection system. New Orleans can flood from multiple directions since
it is surrounded by water on three sides, as seen in Figure 5-8. Prior to Katrina, the levees
were a disjointed group of structures, and many of the levees had been modified many
times to address changing conditions (Rogers 2008). Hurricane Katrina caused many of
these structures to fail, and as part of the post-event examination, the need for a
comprehensive flood protection system became apparent.

Figure 5-8. New Orleans, Louisiana
New Orleans is surrounded on three sides by water, with Lake Pouchetrain to the north,
Lake Borgne, to the east and the Gulf of Mexico to the south.
Source: Bing Maps; http://www.bing.com/maps/.

In New Orleans, rather than rebuilding the previous structures, a coordinated and
redundant flood system was developed. In addition to the levees that will provide
secondary protection, primary protection will come from a $15 billion US coordinated
system of flood gates, levees, pump stations, surge barriers, and habitat restoration. Major
elements of the city’s protection have been designed to provide full protection from a
100-year flood event. Yet, even though the surge barriers might be overtopped by a larger
event, they have been designed survive up to a 500-year storm event without collapse and
Page 87
to reduce flooding (DeSoto-Duncan 2011; USACE 2010; Blake et al. 2011). The protection
system for New Orleans addresses only a portion of the region that suffered damage;
however, the total cost for the surge barrier was about $1 billion US, which just a small
percentage of the approximately $110 billion US in damages from Hurricane Katrina
(Jonkman et al. 2013; Knabb et al. 2005).

Engineered protection has many limitations due to the need to set design conditions, the
need to provide for long-term maintenance and repair, the involvement of a multitude of
owners/operators, the need to function with many other structures, and the possibility that
the structures will be used for purposes that were never intended when they are first built.
But, these limitations can be minimized with careful design, maintenance, attention to
changing event conditions, and system demands. And, as long as development remains in
dynamic coastal areas that will be vulnerable to coastal hazards and extreme events,
engineered protection will remain part of the community’s protection.

Resilience at the Building or Asset Scale. Building and asset scale protection and
adaptation efforts have been used for centuries to accommodate changes in climate and
weather conditions. In many cases, they compare with community-scale responses, but at
a smaller scale. For example, sand bags can be used to protect a community from
flooding or wave overtopping or they can be used to protect a building. Some protection
efforts, such as setbacks from the edge of a bluff or river bank, or elevation above the
flood level need to be included in the initial building siting and design. Sound building
practices, such as codes, also are developed mainly in the initial design and construction
phase of development. Other protection efforts can be added as needed, such as storm
shutters, inflatable barriers, pumps, or water-proof vaults. Other protection efforts can be
installed and removed in response to hazard warnings, such as sand berms, sand bags, or
plywood coverings. These features are discussed in more detail in Chapter Six and in
Tables A-1 through A-5.

One benefit of developing protection at the building or asset scale is that the protection
can match the needs and characteristics of the structure or the location. Setbacks can be
based upon the erosion characteristics of the location and the expected life of the
development. Building elevation can keep important areas of the structure above the
flood zone while allowing uses that can survive floods to occur at lower elevations.
Further, building standards and building codes insure that all construction will meet a
minimum quality of construction to survive routine storms, wind and water forces.
Building design might also provide protect from extreme events. Prior to Hurricane Ike,
several “fortified” houses had been built on Galveston and Bolivar Islands. The structures
had been built to a stricter standard than building code; they had additional freeboard
above the base flood elevation, used waterproofing for the lower elevations, using
strapping and bolts to connect the house to the foundation, and embedded concrete
foundation columns at least 10 feet into the ground for scour protection. While most of
the buildings in the area were destroyed by floodwaters, these buildings remained
standing, suffering only surficial damage from the hurricane.

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Building and asset protective measures can be part of a larger, community scale resilience
and protection plan. For example, if a levee is overtopped, buildings at ground level have
no other protection, whereas buildings that are elevated or protected by sand bags might
have only slight damage. Sections of roadways may benefit from elevation, and roadways
could be placed on top of levees to provide an option for safe evacuation; but, elevation
might be impractical for all roadways within the community.

Resilient Land Use Planning Measures. Most of the resilience measures discussed in
previous sections have provided protection to communities or structures by reducing or
blocking the flooding, wave forces or erosion. Setbacks and elevation are options for
accommodating flooding and erosion. Another option for protecting important
community assets is to move them out of harms’ way or avoid putting them in a
hazardous location. Land use planning measures often address hazards through
avoidance. An added benefit from avoidance is that the undeveloped lands may be able to
serve as overflow areas during flood events, buffers during storms, and open space or
recreation areas during non-events periods.

Land use options can include land acquisition through a fee simple purchase, acquisition
of an easement or of the development rights, or a program of managed retreat. A fee
simple acquisition would enable the community to take the purchased land out of
development and insure that no future development would be exposed to the hazards that
could occur at this location. Such an acquisition would likely take the property off the tax
rolls so this option would cost the community not only the land value but the lost tax
revenues. The community would not be required to provide services to this area, and
these savings might offset some of the land costs for high risk locations. Conservation
easements would only transfer some of the development rights of a property to the
community, allowing development on one portion of the land while keeping the higher
risk portions as open space. In a transfer of development credit program, property owners
acquire the development rights for a high-risk parcel and apply these rights to a land
parcel with a lower risk. The end result is concentration of development in the lower risk
areas, and little, if any development in high risk areas. Finally, a managed retreat program
would reduce the amount of existing development in high risk areas over time. As the lots
narrowed due to erosion or rising sea level or storms, the at-risk portions of the
development would be removed or relocated – retreating from the hazard when the risk
becomes too great.

The various land use options for resilience can be used together or in combination with
community protection, natural features and individual building or asset protection. The
land use options also can focus on known high hazard areas, but can be modified to
address new hazard locations as these locations become apparent. The short-term costs
for some land use measures may seem high, but this will need to be weighed against the
long-term benefits from moving or keeping development from high hazard areas.

Other Elements. Two final resilience elements are insurance and early warning systems.
These are specialized aspects of community resilience that function in coordination with
many of the other protective measures. Insurance provides a financial safety net for those
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situations when damage does result from a hazardous event and the community needs
resources to rebuild. Early warning systems provide a life safety function, notifying
people of the need to take shelter or evacuation. As has been seen from many of the
recent disasters, notification of an approaching storm, hurricane or tsunami can save
lives. Also, many of the temporary protective measures from surge barriers to sand bags
and shutters are only effective if there is sufficient warning to close or deploy them.

Insurance does not reduce risks; however, it is a risk sharing mechanism that can help
lessen the impacts from a disaster. The Hyogo Framework for Disaster Risk Reduction
(UNISDR 2005) includes the need for options to share financial risk. Insurance is the best
known method for sharing financial risk; other methods include micro-insurance
(targeted, low coverage policies), reserve funds (normally set up by governments to cover
unexpected losses), risk pooling (to spread risks throughout a geographic region), or
insurance-linked securities (such as catastrophic bonds) (Warner et al. 2009). Each of
these methods can help provide financial resources for post-disaster recovery. Public
insurance can help restore community functions, and private insurance can enable
members of the community to rebuild while minimizing reliance upon public resources.

Information on the locations, intensity and frequency of hazard events is necessary for
insurance to work for both parties -- the insurer and the insured. Such information forms
the basis for the premiums and helps determine whether insurance will offer advantages
to both parties. Due to this need for hazard information, reinsurance groups such as
Munich Re and Swiss Re, maintain globally some of the most comprehensive
information on climate risk and natural disasters., Historically, insurance has been used
primarily in industrialize nations, possibly due to the more systematic collection of
disaster information and to a greater concentration of monetarily values assets. But use
of insurance and micro-insurance is growing in developing nations (Warner et al. 2009)
as more information of hazard events and disaster risk becomes available.

One concern about reliance upon insurance for disaster reduction is that insurance can
encourage riskier development than might otherwise occur (Kunreuther 1996). Risk
pricing (premiums that reflect the level of risk) can discourage new development in high
hazard areas, but can put an excessive burden on existing development. Insurance alone
cannot address all issues with disaster reduction. For resilience, communities need to
develop land use planning that supports avoidance of high hazard areas as a complement
to insurance (Kunreuther 1996; Warner et al. 2009) Chapter Six and Tables A-1 through
A-5 discuss insurance and other resilience measures in more detail.

Chapter 6
Index for Evaluating
Resilient Coastal Systems

The greatest glory in living lies not in never falling,
but in rising every time we fall.
Nelson Mandela

6.0 Introduction
Shoreline protection provides community resilience for many difference conditions,
ranging from the onset of a disaster to routine or non-disaster phases or time periods. The
value of shore protection during a disaster will be dependent upon the specific conditions
of the event and the protective features available to the community at the time of the
event. The risk reduction of shore protection can only be developed on a site- and event-
specific basis. However, the direct economic, environmental and social/cultural benefits
of shore protection features can be more directly developed for the protection, regardless
of site conditions. Additional site-specific benefits from shore protection, defined as
secondary benefits, are associated with the inland assets that are protected. These direct
and secondary benefits that can result from shore protection are incorporated here into a
Coastal Community Hazard Protection Index (CCHPR Index). The CCHPR Index is first
developed for general application to include the variety of shore protection features that
are typical of many communities, and is then applied to the Ocean Beach coast of San
Francisco, California to demonstrate the application and utility of the CCHPR Index for
evaluating coastal community resilience.

6.1 Determining Community Resilience from Protection Measures
As discussed in Chapter Five, community protection is provided by a number of different
protective features, ranging from land use and natural features, to engineered structures,
asset protection, early warning systems and insurance. Each of these provides different
types of protection and fits differently into the overall community character and fulfills
different needs. Many protective features provide more community value than protection
and these values are part of the features overall utility to the community. However, in
evaluating protective elements, the initial determination for utility must focus on
protection, and, this need for protection should correspond strongly with the assets at risk.
Thus, a large number of significant assets at-risk would indicate a high protection need;
whereas, a few small, replaceable at-risk assets would need far less protection. With this
correlation between protection and at-risk assets, overall community protection can be
improved by increasing protection of the at-risk assets, or reducing the number and
significance of assets at-risk. Some community assets may be of such importance that
dedicated protection is warranted to maintain protection and insure rapid recovery from
extreme events.

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An evaluation of protection needs to consider how different features provide protection,
the initial and maintenance costs for the protection, how it can interact with other
protective features, and the consequences of failure. The options discussed in Chapter
Five are all included in Tables A-1 and A-2, both provided as Appendices. Table A-1
provides general information about many protective options, including how the option is
typically used, how it provides protection, the general benefits and costs, the groups that
normally would implement the option and how long it will take to implement.

Creative uses for shore protection continue to be developed, and these options are not an
exhaustive list. The protection methods provide either hard or soft resistance which is not
to be confused with hard or soft protection. The type of resistance refers to the way the
feature provides protection. If the feature primarily blocks wave forces or erosion or
provides a physical barrier to flooding, then it is considered to be hard resistance. If the
feature dissipates wave energy, drops flood levels, or reduces erosion, it is considered to
be soft resistance. The column entitled ‘normal acting party’ lists the groups or
organizations that normally undertake these measures. These are not the only groups that
could undertake the actions, but large or very expensive protection methods may be
options for the bigger community groups while the smaller, more decentralized methods
may be more appropriate for property owners. Also, the list indicates that community
resilience is a broad community effort and that it is not limited to one or two groups.

Table A-2 provides details about the effectiveness of the options, such as the spatial area
that can be protected, the time period over which the protection will be effective, how the
protection might change with climate change, initial costs, maintenance needs, and how
the protection can fail. Some protection costs are given as a monetary range, wherever
there are enough reported costs to support these values. Often the costs are too specific to
the community, to the resource, or to the multiple benefits that might arise from the
action; and in those cases, the costs are only provided qualitatively. The failure mode of
protection is quite important. Options that can provide some level of protection, even
after failure, can be far more valuable during recovery than protection that loses all
protective value. In the worst case, protection that collapses adds to the damages during
the event, or adds to the debris that must be removed as part of the recovery.

Table A-3 provides details about the protection mode for each option, and the specific
values they have for the various phases of a disaster – pre-event, during the event,
recovery immediately after the event, and the period after the immediate recovery until
warning of the next event. Since many of the types of protection function in similar ways
or provide similar types of protection, there is a lot of redundancy in this table. To reduce
some redundancy, several options have been lumped together, where appropriate. For
example, the benefits from a wide beach are not dependent upon the source of the sand,
so the many sand source options in Tables A-1 and A-2 are combined in Table A-3 into
the general heading of beach enhancement. Likewise, the land use options for open space
have been combined in Table A-3.

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Each coastal community will have a unique mix of protection. Some may have offshore
protection, such as reefs or breakwaters. These features reduce incoming wave energy
and provide the first line of protection from hazards. However, it is important to identify
gaps in these features since wave energy and currents can intensify in the gaps. Closer to
shore, communities might be protected by marshes, sea grasses, or a beach that can
reduce and dissipate wave energy, as well as accommodate changing water levels and
shifts in sediment erosion and accretion. Immediately inland of the beach may be dunes
or coastal bluffs that provide protection by either resisting the wave energy that exceeded
the beach capacity, or augmenting and supplementing the beach volume and beach area
through erosion. Engineered structures may replace or augment the protection from bluffs
and dunes, and coastal assets may have been designed with their own protection, through
setbacks, elevation, flood-proofing, storm shutters, and such. Resilience is the combined
interactions of all these elements together.

An understanding of community resilience can be developed from an inventory of
protective features – man-made and natural -- and an assessment of their individual and
combined effectiveness in protecting from coastal hazards. Protective efforts provide
protection in different ways. Some, like walls and barriers, block wave forces and high
water levels and halt erosion; others, like breakwaters and marshes attenuate wave
energy, reduce water levels, and slow erosion. However, these protective features also
need to be evaluated relative to overall community values and benefits under both day-to-
day and episodic event conditions. Overall resilience of coastal protection has four
components or phases, the pre-event actions that can provide temporary or event-based
improvements, the protection and value during and immediately after the event, the
immediate recovery, and then the on-going use until the next event. The values and
benefits of various protection efforts change from phase to phase. For example, a tsunami
warning siren may provide some peace of mind on a day-to-day basis, but its highest
value is for pre-event life safety.

This type of evaluation is in line with the normal way that communities undertake a
vulnerability study: identifying existing protection and at-risk assets, and examining
possible changes over time. With the current focus on the increased vulnerability of
communities to climate change, sea level rise projections and scenario analyses are
normal components of coastal vulnerability studies. When sea level rise is included in the
analysis, both the protection and the assets at-risk will be modified with time and
changing hazard conditions. The timing for sea level rise needs to be considered if the
structural or ecosystem functions changes with time. Shoreline erosion provides another
element of temporal and spatial change that needs to be included. Non-engineered forms
of protection, such as beaches or wetlands, and the changes in protection value due to
deterioration of the feature are often not included in vulnerability assessments. These are
both important aspects of coastal protection and should be part of more analyses.

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Coastal protection is not static. Protection provided by natural systems can ebb and flow
with changes to the natural system. For beaches, this can occur from seasonal changes in
beach width, or from long-term erosion or accretion trends. For reefs, mangroves,
wetlands, and other living systems, protection can change with the health of the
ecosystem, or with the seasonal changes in vegetation growth. Over a number of years,
the protective value of these systems may also depend upon whether there is space to
migrate and adjust to coastal changes. Such adjustments will be critical for these systems
to remain effective with rising sea level.

Intact reefs, marshes, mangroves and wetlands tend to have a complex, overlapping
structure that minimizes wave focusing within the structure. Natural, intact ecosystem
protection rarely transfers coastal impacts to an adjacent area. Wave focusing may be a
problem at the ends of the structures if the ecosystem features stop abruptly, rather than
taper into the adjacent terrain. If gaps have been constructed through reefs or wetlands for
navigation or ship traffic, the gaps can focus energy and concentrate impacts on the
shoreline projection of the gap.

End or edge effects and energy focusing is a regular concern with built protection.
Designs often include tapered ends and edges to minimize the transition from the built
structure to the untreated or native material; however, these efforts cannot prevent all end
or edge effects. Further, as the native materials continue to erode or be modified by
coastal processes, the differences between the built and native areas will increase.

Built structures, while seemingly unchanged, can lose effectiveness if not maintained;
with regular maintenance, these systems can remain close to their original design
conditions for a number of years. However, with rising sea level the protection level will
decrease, even if the design level of protection is maintained. Major changes to the
structures might be necessary for the structures to provide an equivalent level of
protection with rising sea level. If the structure is neither modified nor maintained, its
effectiveness would drop due both to the expanding gap between the hazard conditions
used in the original design and the actual hazard levels in addition to the general drop in
effectiveness due to deterioration.

Land use protection options, such as setbacks, conservation easements, and land
acquisitions will remain effective over time, unless the area is experiencing erosion. In
locations where erosion is occurring, the effectiveness of these options will reduce with
time. Sea level rise may increase erosion, and further reduce the time period over which
these options provide utility. But, if these setbacks, easements or acquisitions can
continue to move inland with some identified shoreline feature, their utility can be
restored. Eventually, these easements are likely to meet an inflexible barrier, such as
major roadway, utility corridor or high density development. If the setbacks and
easements are used on non-erosive land to provide flood detention or overflow areas,

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their utility may last for many years and only decrease, if flood levels increase due to
climate change.

Ewing and Synolakis (2012) compared the protection that could result from various
maintenance efforts for a hypothetical system of engineered and natural protection
systems. The alternatives that were examined for a hypothetical community were:
• Do Nothing: community does nothing with any protective efforts; the
effectiveness of the structures deteriorates over time; hazard conditions remain
constant over time; if the structures are damaged, they are replaced or
maintained to their original design conditions.
• Modified Status Quo: community maintains protective efforts at current
effectiveness; hazard conditions remain constant over time; if the structures
are damaged, they are replaced or maintained to 100-year design conditions or
better
• Worsening Hazards plus Do Nothing: community does nothing with any
protective efforts; the effectiveness of the structures deteriorates over time;
hazard conditions worsen over time; if the structures are damaged, they are
replaced or maintained to their original design conditions.
• Worsening Hazards plus Modified Status Quo: community maintains
protective efforts at current effectiveness; hazard conditions worsen over time;
if the structures are damaged, they are replaced or maintained to 100-year
design conditions or better.

The protective resilience of the hypothetical community examined by Ewing and
Synolakis (2012) assumes that resilience from the various elements is additive. The
resilience benefits from an emergency warning program assume that the evacuation and
protection effects will be independent of the scenario. A short warning time would
provide the opportunity for evacuation and to shut off essential equipment, close flood
gates, and seal some critical tunnel openings. A somewhat longer warning time would
also enable ships to leave port and go to deeper water; property owners could place sand
bags around storm drains and building entrances and close storm shutters; and more
storm preparation steps could be undertaken throughout the community. The scenarios
assume that recovery and on-going restoration may take multiple years for the various
protection elements. The scenarios also assume that repairs will focus on the largest
engineered systems first so as to ensure their continued presence and that this could
initially draw some resources away from the more local or site-specific elements. With
this assumption, the more localized, usually smaller-scale systems would take longer to
recover after a large event than after a small event.

One clear observation from the comparison of the different maintenance scenarios was
that an early warning system will be a significant element of resilience in those
communities that do little, if anything, to maintain or improve existing protective
features. Also, natural systems provide the only improvement in resilience for the “do-

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nothing” approach. As would be expected, the only scenario to improve resilience over
time is the one in which the protective features are both maintained and modified for
rising sea level conditions. However, if structural protection is brought up to the 100-year
design level during structural upgrades, as depicted by the “modified status quo,”
resilience will improve gradually. Eventually, a large turnover in protective features to a
higher design level would only occur following an extreme event that damages or
destroys even structures built to and continuing to perform at the 100-year design level.

An examination of resilience only in terms of coastal protection overlooks many of the
important features and values of the coast. As discussed in Chapters One and Two, many
of the aspects of coastal communities that make them important, such as recreation,
tourism, fisheries, habitat, and water quality come from the coastal lands and not from the
engineered structures. As noted in Chapter Five, the multi-purpose benefits from coastal
protection elements cannot be overlooked. These benefits come from the economic,
environmental and social/cultural contributions that are provided by the protection. There
can be
• Economic value, excluding the project costs, such as fisheries, changes to tax base or
increased revenues
• Environmental value, such as improved air or water quality, and ecosystem
enhancement;
• Social/cultural values, such as recreation, open space, quality of life.

Each type of protection can provide both direct and secondary benefits. Direct benefits
are those benefits that have an immediate connection to the protection, as, for example
the environmental values that marshes might provide by improving water quality.
Secondary benefits are those improvements that can accompany the protection, often
associated with what is being protected. For example, shore protection would provide a
secondary environmental benefit, if it were to prevent toxic or hazardous material in a
land fill from getting into the marine environment. Table 6-1 summaries some of the key
benefits, or costs, associated with each value.

Table 6-1 Direct and Secondary Community Benefits from Coastal Protection
Direct Benefit from protection Secondary Benefit from what is protected
Economic
Value
Improve navigation
Tourism
Tax base
Revenues
Fisheries
Commercial Harbors
Fishing Harbors
Roads and Rail Corridors
Utilities
Business continuity
Jobs
Environmental
Value
Ecosystem habitat
Air Quality
Water Quality
Landfills
Chemical & Industrial Plants
Water treatment plants
Social/Cultural
Value
Coastal Access
Recreation
Recreational Boating and Fishing
Houses

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Quality of life Parks
Trails and Access
Schools
Hospitals

The economic, environmental and social/cultural values of the different protection
options are presented in Table A-4 for their values during the recovery phase, and in
Table A-5 for the period between recovery until the warning for the next event. The
benefits of these protection options for the pre-event and the event are also important, but
since these are the two phases of a disaster where protection is of key importance and, for
those phases, the non-protective values are assumed to be of little importance.

The economic, environmental and social/cultural benefits of coastal protection are most
apparent during the non-event periods, or the on-going phase. Also, for most coastal
communities, the non-event periods of time will be far longer than the pre-event and
event times. Figure 6-1 shows the temporal distribution of pre-event, event, recovery, and
on-going activities, for various return period events. The first three columns in Figure 6-1
show the annual distributions for small events with a frequent recurrence interval. The
last two columns of Figure 6-1 show the cumulative times over a 50-year period,
including either one 50-year event or one 50-year and one 100-year event that might
necessitate a multi-year recovery period. The time period for each phase are based upon
past events and professional judgment.

Figure 6-1. Temporal Distribution of Four Disaster Phases - Various Disaster Events
0%
20%
40%
60%
80%
100%
1-yr return period From 1-yr to 50-yr
return period
50-yr return
period
Cumulative over
50 years
Cumulative over
50 years, with a
100-year event
Temporal Distribution of the Four Phases
of a Disaster
Pre-
Event
Event
Recovery

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The temporal distributions in Figure 6-1 assume that a significant storm event will occur
2 weeks out of each year; recovery for any event with a 25-year return frequency or
greater will require two months for recovery and a 50-year event will require six months
for recovery. It may be overly conservation to assume that communities will spend one
week each year on pre-event preparations. Likewise, it may be overly conservative to
assume that any event with a return frequency over the 25-year event will require two
months for recovery. Thus, over an average 50-year period, a community will need two
months for storm recovery every other year. These high recovery times also assume that
the overall community protection is low and that small 25-year return period events can
disrupt the community for months and a time. Most developed coastal communities have
established protection that will be adequate for these moderate events. Yet, even
assuming these rather high amounts of time allocated to the pre-event and recovery, on-
going activities will still be the norm almost 90% of the time.

For small, regularly recurring events, such as the 5 to 10 year return period events, the
duration of the pre-event could be 5 or 7 days for a slow-moving storm or hurricane, or
only 15 or 20 minutes for a fast moving tsunami. The events themselves can persist in a
coastal community for perhaps half a day up to a week. Together, the pre-event and event
would last, at most, two weeks. Often, the time period would be much shorter, and the
transition from event to on-going activity phase would be rapid, with little, if any time for
recovery. For the small 5 or 10-year recurrence events, the non-event time would be all
but the week or two during which the event is being anticipated or is happening.
Protection from these small, frequent events is important; but, the time period over which
these protective features will function solely as protection is quite small. For the bulk of
the time that they are part of the community function, these protective elements will be
valued or evaluated for their other benefits, and their function within the larger
community environment will be important.

Larger events that have a 1% or less annual probability of occurrence (such as the 100-
year, 250-year, 500-year and 1,000-year events) are the events that can cause massive
community damage and require years for recovery. The time for the pre-event and the
event would be similar for the occurrence times for smaller events; however, these events
are likely to cause damage and require a longer interval of recovery time prior to
transitioning to on-going activities. This extended period for recovery increases the time
that the community is focused on the disaster, and highlights the benefits from intact
protection systems. If coastal protection has been destroyed or compromised, then the
recovery efforts will be vulnerable to small, but frequent events and will be delayed or
interrupted by these smaller storms.

As seen from recent large events, the recovery phase may take months or even years.
Based on field investigations immediately after Hurricane Ike and one year after then
event, the main part of Galveston that had been protected by the Galveston Seawall was

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functioning and recovered within a year after Hurricane Ike, but surrounding areas that
did not have effective protection, such as Bolivar Peninsula, were only starting to rebuild
about a year after the event. In Japan, some of the major commercial or resource-based
activities with economic or environmental value (see Table 6-1), like port facilities and
fishing operations, had been reestablished within one-year after the 2011 Tohoku
earthquake and tsunami; other activities were still being restored (ASCE-COPRI-PARI
2013). In these major but infrequent events, recovery can dominate the various phases of
the disaster and the role of protection in recovery may be as critical as its role in the main
event. And, recovery can greatly benefit if protective elements continue to function, even
with diminished capacity. Post-disaster protection can enable recovery efforts to continue
during small storm events and can be a foundation for future protection because features
that remain functioning and in place do not add additional burden to the clean-up efforts.

Observations of major disaster events, the analysis of the time a community will spend in
each of the different phases of a disaster, and the plots of event and recovery from
Chapter Five all show that recovery and on-going activities are temporally the dominant
phases of a community. There are many ways to achieve some specified level or
protection; the various options described in Tables A-1, can be used or combined for
protection. The dominance of the recovery period and time on-going activities highlights
the need for protection options that can function and provide utility or value during these
times. The value of coastal protection to community resilience should be based on their
combined value for all the phases of a disaster.

6.2 Coastal Community Hazard Protection Index
Community resilience from coastal hazards needs to combine multiple attributes of
protection. Focusing coastal protection on storm return frequency or a particular water
level may provide insight into the available protection level. However, this approach fails
to address the usefulness of the protection if it has been damaged during the storm or
wave event, or the economic, environmental or social/cultural values of the protective
feature through all the disaster phases of the community. The evaluation of coastal hazard
protection will occur at a number of different scales, from the micro, asset-specific scale
to determine when to implement maintenance, to the detailed, community-wide scale to
determine the benefits and costs of a billion dollar investment in a new engineered
protection structure.

As highlighted in some of Tables A-4 and A-5, a number of studies have attempted to
determine the costs for various types of protection and the benefits for the various non-
market values, such as environmental and social/cultural values, from various coastal
features (for example, Blankespoor et al. 2012; and deGroot et al 2012). These
quantifications can be very important for investment decisions. However, planning and
examination of resilience options could begin long before any detailed analysis of
individual additions or changes to overall coastal hazard protection for a community. The

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Coastal Community Hazard Protection Resilience Index (CCHPR Index) will assist
communities with their overall examination of resilience and help highlight the main
weaknesses or limitations in the current resilience efforts.

The CCHPR Index enables a community to undertake a general examination of the
existing protection, determine the major values that can be attributed to this protection
and compare this existing situation options for the future, such as the maintenance
options examined in Chapter Five, or to determine the overall change in benefits from
introducing changes to the coastal area. These changes can arise from changes to the
available protection, or to the community assets that are most at risk. The Index is
developed from the key elements of the existing protection using community-specific
values or those provided in Appendix A. Table 6-2, the basic framework for the CCHPR
Index, extracts six key attributes for the array of protection options covered in Tables A-1
through A-5. These main attributes are:

• The type hazard addressed by the protection element.
• Whether protection element relies upon soft or hard resilience.
• Value from protection element in failure mode (partial, null, negative).
• Economic values of the protection element, direct and secondary.
• Environmental values of the protection element, direct and secondary
• Social/cultural values of the protection element, direct and secondary.

These first three characteristics have already been discussed and the information provided
in Table 6-2 should be clear. The adjectives hard and soft characterize the type or
resistance; full, partial or negative failure mode identifies whether the protective feature
provides partial protection, no protection, if it in failure mode it contributes to damages.

The economic, environmental and social/cultural values summarize the information from
Table A-4 and A-5. In these tables, the direct economic, environmental and
social/cultural values have been evaluated as having either a positive or negative value
that is high, medium, low or no value. These qualitative values are assigned quantitative
values of 3 for high, 2 for medium, 1 for low and 0 for no value. The direct economic,
environmental and social cultural values in the CCHPR Index are the combined values
for each protection element derived from both recovery and on-going activity phases,
with the recovery phase weighted as 25% of the total value and on-going activities phase
weighted as 75%. These weightings are based upon the temporal distributions from
Figure 6-3.

Beaches are one of the primary types of protection for many communities. From Tables
A-4 and A-5, beaches generally have slight to moderate economic value during recovery
since tourism is not likely to be a strong community element during recovery. But,
beaches would have a moderate environmental value and provide a high social/cultural
value to the community members as they participate in recovery. Thus for the recovery

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phase, beaches are given values of 0 - 2 for economic value (average value of 1), 2 for
environmental value and 3 for social/cultural value. Under ongoing activities, beaches
would foster some tourism and the economic value would increase to 3; the
environmental and social/cultural values would remain the same as for recovery
conditions. Combining the recovery and on-going condition values by the 25% and 75%
weighting respectively, the index values for beaches are 2.6 for economic value, 2 for
environmental value and 3 for social/cultural value.

Revetments provide a second example of the index. During recovery, revetments would
have a low economic value of 1 since they might encourage more rapid recovery. These
structures can capture debris and trash so their environmental value would be neutral to
slightly negative (0 to -1) and they would have no social/cultural value. During routine or
on-going conditions, revetments would provide no economic value to the community;
their environmental value would be slightly to moderately negative (-1 to -2) since they
would displace beach habitat; and their social/cultural value moderately to highly
negative (-2 to -3) because they would interfere with along-shore beach access, recreation
and the overall beach experience. Based on these values and the same 25/75 weighting,
the index values for revetments are 0.3 for economic, -1.3 for environmental and -1.9 for
social/cultural.

The CCHRP Index also includes secondary values. The secondary values are community-
specific and derive from the types of development that is being protected, as discussed
previously and noted in Table 6-1. Like the direct values, these secondary values are
assigned a value of 3 for high, 2 for medium, 1 for low and 0 for no economic,
environmental or social/cultural value.

The merits of this quasi-qualitative index are that it allows flexibility in the evaluation
and development of a resilience index, while keeping economic, environmental and
social/cultural values on an equal basis. Communities could use more elaborate values if
they choose, assign different numerical values to the high, medium and low, or even add
other ratings such as very high or of irreplaceable value. The CCHPR Index does not
assign different levels of importance or weights to economic, environmental or
social/cultural values, although communities could also assign different weightings to
these if they were so inclined.

Neither an early warning system nor an insurance program readily fit into the CCHPR
Index, but they are very important to overall community resilience. In most situations,
communities may choose to evaluate these two elements separately from the more
traditional protection. An example for the San Francisco open ocean coast is provided to
demonstrate how this CCHPR Index would be applied.

Page 101
6.3 CCHPR Index Application to Ocean Beach, San Francisco, CA

Ocean Beach is San Francisco’s western border and the city’s open ocean coast. It is
approximately 5.8 km (3.6 miles) long, from Point Lobos in the north to bluffs in Fort
Funston in the south. Ocean Beach was once part of vast beach and dune system;
however today, many of the dunes have been covered by houses, roads, and parking;
some dunes have been vegetated to form part of the Golden Gate National Recreation
Area. Today, the dominant features along Ocean Beach are the Great Highway,
pedestrian paths, parking areas, and several large seawalls. Utility corridors for electrical
power, sewer and storm water run under the Great Highway. Immediately inland of the
Great Highway are restaurants, the SF zoo and other visitor serving facilities, homes, and
a wastewater treatment plant.

The Great Highway was built on top of the dunes, on land set aside by the city for a
public highway. But, this location placed the highway at risk from wave damage, and
soon after the City of San Francisco started building the roadway, the City also began
building a large, seawall to protect it. The first and northernmost seawall, the
O’Shaughnessy Seawall, is almost 1,310 m (4,300 ft) long. This seawall provides for
steps down to the beach, and it included a series of six platforms or bleachers that can be
used for seating. South of the O’Shaughnessy Seawall is the 200 meter-long (660 foot-
long) Taravel Seawall and the 885 meter long (2,900 foot-long) Great Highway Seawall.
These three walls together armor much of the Great Highway and demarcate the inland
boundary of the northern and central sections of Ocean Beach. No massive seawall has
been built along the southern section of Ocean Beach, however, several temporary
revetments and beach nourishment projects have been installed in this area (known as
South of Sloat) to protect the road and parking areas from erosion.

The Ocean Beach area was used as a test case for application of the CCHPR Index
because it is has a mixture or protection features and inland development. Further, the
City of San Francisco has spent several years studying this coastal section and developing
several options for addressing erosion while maintaining many of the important
economic, environmental and social/cultural features of this area, and it is an area with
which the author of this dissertation is familiar having written about this beach and
served on both the Ocean Beach Planning Committee and the Ocean Beach Technical
Advisory Committee for the City.

Page 102

Figure 6-2. Ocean Beach, San Francisco (2003) looking south. The O’Shaughnessy
Seawall is in the foreground, with the Great Highway and Taravel Seawalls farther south.

Tables 6-3 and 6-4 show the application of the CCHPR Index to Ocean Beach, the Pacific
Ocean shoreline of San Francisco, California. Table 6-3 shows the different protection
elements which are present along the shoreline. For many sections of the shoreline, there
are multiple protective features. When that is the case, the values from each protective
element are included in the table. The value is assigned to the section of coast where the
protection occurs, multiplying the protection value by the shore length. Similarly, the
secondary values for what is being protected are developed by multiplying the secondary
values by the shoreline length. The total value for the beach area is summed for the
individual sections and weighted by the total shoreline length.

The tabulation of economic, environmental and social/cultural values for Ocean Beach is
shown in Table 6-4. Table 6-5 shows just the summary of the direct and secondary
values weighted by length. The full strength of these weighted values will be clearer
once the index is developed for more communities. However, some aspects of the
shoreline and the community resilience are apparent without comparison to other
locations.

The shore protection features provide a mix of direct economic, environmental and
social/cultural values that have high economic and social/cultural value and slightly

Page 103
lower environmental value, assuming these are weighted equally. The secondary assets
have high economic and environmental value, but low social/cultural value.

Overall, the economic values from the beach and protection options are somewhat higher
than the features being protected (the direct economic value is 3.6 and secondary
economic value is 2.7). Much of the direct economic values derive from the beaches and
dunes, suggesting that the City would benefit economically from greater focus on these
natural protective assets. The difference between the direct to secondary values is even
more the case for the social/cultural values of the existing coastal features. The beach and
dune values far outweigh the social/cultural values of the inland assets.

The environmental values present a different situation than the economic and
social/cultural values. The environmental values from the shore protection features are
less than the environmental values of what is being protected. Since a sewer line and
wastewater treatment plant are both close to the shoreline, the high environmental
importance of protecting these assets is apparent. Damage to these backshore structures
might be more significant environmentally that damage or loss of the protection features.
The environmental value of these secondary assets derives from their water quality
benefits. Damage to the transport line or to the plant could have significant environmental
impacts. Efforts to improve protection of these assets would need to consider how the
protection steps might change the direct economic and social/cultural values that are
provided now by the beach and dunes. Options to reduce the environmental value of the
secondary assets could improve the relative importance of the direct environmental
values, without detrimental impacts to the direct economic and social cultural values
from the current protection elements.

The CCHPR Index can be used to explore aspects of community resilience, and also to
evaluate the significance of future changes to the coast. Following the Ocean Beach
example, options to reduce the secondary values that depend upon protection would
reduce the overall importance of the protection whereas options to increase the secondary
values would put greater emphasis on protection, or focus more attention on protection
that provides partial protection in the failure mode.
Table 6-2 Coastal Community Hazard Protection Resilience Index (CCHPR Index)
Protective Element Protection Failure
Mode
Economic
Value
Environmental
Value
Social/Cultural
Value
Type Shore
Length
Erosion
Hard/Soft
Waves
Hard/Soft
Flooding
Hard/Soft
Partial, Null,
Negative
Direct 2ndary
Site
specific
Direct 2ndary
Site
specific
Direct 2ndary
Site
specific
Beaches S S S Partial
2.6

2.0

3.0

Sand Back-
pass
S S S Partial
0.3

-1.0

2.0

Beach Berm S S S Null
1.0

-1.0

2.0

Groin S S S Partial
1.0

-1.0

0.0

Jetty S S S Partial
3.0

-0.8

1.5

Perched
Beach
H S S Null
0.0

0.5

1.3

Breakwater S S S Partial
3.0

2.0

2.0

Floating
Breakwater
- S - Negative
1.5

-1.5

0.0

Enhanced
Delta
S S S Partial
1.0

0.8

0.0

Headlands S S S Partial
1.0

0.8

0.0

Dewatering S S S Null/Negative
0.8

-0.1

0.0

Wetlands S S S Partial
1.0

3.0

1.0

Dunes S S S Partial
1.8

2.0

3.0

Reefs S S S Partial
1.0

3.0

2.0

Habitat
Buffers
S S S Null
-2.0

2.0

2.0

Living
Shores
H S S Partial
1.0

2.0

2.0

Levee H H H Null/Negative
0.3

-1.1

0.0

Horizontal
Levee
S S/H S/H Partial
0.3

1.4

0.0

Revetment H H H Partial
0.3

-1.3

-1.9

Dynamic
Revetment
H H H Partial
0.0

-0.5

-1.1

Seawalls H H H Null
0.3

-0.8

-1.1

Page 105
Table 6-2 Coastal Community Hazard Protection Resilience Index (CCHPR Index) (Continued)
Protective Element Protection Failure
Mode
Economic
Value
Environmental
Value
Social/Cultural
Value
Type Shore
Length
Erosion
Hard/Soft
Waves
Hard/Soft
Flooding
Hard/Soft
Partial, Null,
Negative
Direct
2ndary
Site
Specific Direct
2ndary
Site
Specific Direct
2dary
Site
Specific
Sand Bags H H H Null/Negative
-0.3

-1.4

-1.9

Surge
Barrier
H H H Negative
0.3

0.0

0.0

Building
Protection
H H H Null/Negative
1.5

0.3

0.6

Land
Acquisition
S S S Null
-2.0

2.5

1.6

Insurance - - - Negative
0.0

-0.3

0.5

Warning
System
- - - Negative
0.6

0.3

0.3

Page 106
Table 6-3. CCHPR Index – Elements for Ocean Beach, San Francisco, CA
Protective Element Protection Failure
Mode
Economic
Value
Environmental
Value
Social/Cultural
Value
Type Shore
Length
(m)
Erosion
Hard/Soft
Waves
Hard/Soft
Flooding
Hard/Soft
Partial,
Null,
Neg.
Direct 2ndary
Site
specific
Direct 2ndary
Site
specific
Direct 2ndary
Site
specific
Beaches 500 S S S Partial
2.6
road
2.0

3.0
parking
Seawalls 500 H H H Null
0.3

-0.8

-1.1

Beaches 400 S S S Partial
2.6
road
2.0
Sewer line
3.0
parking
Seawalls 400 H H H Null
0.3

-0.8

-1.1

Beaches 450 S S S Partial
2.6
road
2.0
Sewer line
3.0

Seawalls 450 H H H Null
0.3

-0.8

-1.1

Dunes 1,250 S S S Partial
1.8
road
2.0
Sewer line
3.0

Beaches 1,400 S S S Partial
2.6
road
2.0
Sewer line
3.0

Seawalls 1,400 H H H Null
0.3

-0.8

-1.1

Beaches 940 S S S Partial
2.6
road
2.0
Sewer line
3.0

Dunes 900 S S S Partial
1.8
Road
2.0
Sewer Line
3.0

Dunes 20 S S S Partial
1.8
Road
2.0
Sewer Line
3.0
Bath
room
Dunes 120 S S S Partial
1.8
Road
2.0
Sewer Line
3.0

Beaches 235 S S S Partial
2.6
Road
2.0
Sewer Line
3.0

Dynamic
Revetment
235 H H H Partial
0.0

-0.5

-1.1

Sand
Back-pass
235 S S S Partial
0.3

-1.0

2.0

Page 107
Protective Element Protection Failure
Mode
Economic
Value
Environmental
Value
Social/Cultural
Value
Type Shore
Length
(m)
Erosion
Hard/Soft
Waves
Hard/Soft
Flooding
Hard/Soft
Partial,
Null,
Neg.
Direct 2ndary
Site
specific
Direct 2ndary
Site
specific
Direct 2ndary
Site
specific

Beaches 240 S S S Partial
2.6
Road
2.0
Sewer Line
Wastewater 3.0

Beaches 250 S S S Partial
2.6
road
2.0
Sewer Line
Wastewater 3.0

Revetment 250 H H H Partial
0.3

-1.3

-1.9

Warning
System
5600 - - - Negative
0.6

0.3

0.3

Total
Length
5,600

Page 108
Table 6-4. CCHPR Index – Application to Ocean Beach, San Francisco, CA
Ocean Beach, CA
Protection
Economic Values Environmental Values Social/Cultural Values
Type Length
(m)
Direct
Value
# 2ndar
y Site
Value
Val
.
# Direct
Value
# 2ndary
Site
Value
Val
.
# Direct
Value
# 2ndary
Site
Value
Val. #
Beaches 500 2.6 1300 road 2 1000 2 1000 0 3
150
0 parking 1 500
Seawalls 500 0.3 150 0 -0.8 -400 0 -1.1 -550 0
Beaches 400 2.6 1040 road 2 800 2 800
Sewer
line 3 1200 3
120
0 parking 1 400
Seawalls 400 0.3 120 0 -0.8 -320 0 -1.1 -440 0
Beaches 450 2.6 1170 road 2 900 2 900
Sewer
line 3 1350 3
135
0 0
Seawalls 450 0.3 135 0 -0.8 -360 0 -1.1 -495 0
Dunes 1,250 1.8 2250 road 2 2500 2 2500
Sewer
line 3 3750 3
375
0 0
Beaches 1,400 2.6 3640 road 2 2800 2 2800
Sewer
line 3 4200 3
420
0 0
Seawalls 1,400 0.3 420 0 -0.8
-
1120 0 -1.1
-
154
0 0
Beaches 940 2.6 2444 road 2 1880 2 1880
Sewer
line 3 2820 3
282
0 0
Dunes 900 1.8 1620 Road 2 1800 2 1800
Sewer
Line 3 2700 3
270
0 0
Dunes 20 1.8 36 Road 2 40 2 40
Sewer
Line 3 60 3 60
Bath
room 1 20
Dunes 120 1.8 216 Road 2 240 2 240
Sewer
Line 3 360 3 360 0
Beaches 235 2.6 611 Road 2 470 2 470
Sewer
Line 3 705 3 705 0

Page 109
Ocean Beach, CA
Protection
Economic Values Environmental Values Social/Cultural Values
Type Length
(m)
Direct
Value
# 2ndar
y Site
Value
Val
.
# Direct
Value
# 2ndary
Site
Value
Val
.
# Direct
Value
# 2ndary
Site
Value
Val. #
Dynamic
Revetment 235 0 0 Road 2 470 -0.5
-
117.5 0 -1.1
-
258.
5 0
Sand Back-
pass 235 0.3 70.5 Road 2 470 -1 -235 0 2 470 0
Beaches 240 2.6 624 Road 2 480 2 480
Sewer
Line
Waste
water 6 1440 3 720 0
Beaches 250 2.6 650 road 2 500 2 500
Sewer
Line
Waste
water 6 1500 3 750 0
Revetment 250 0.3 75 Road 2 500 -1.3 -325 0 -1.9 -475 0
Warning
System 5600 0.6 3360 0.3 1680 0 0.3
168
0 0

Total Length 5600
1993
2
1485
0
1221
3
2008
5
185
07 920
Weighed by
length 3.6 2.7 2.2 3.6 3.3 0.2

Table 6-5 Normalized Values for Shore Protection from Ocean Beach, San Francisco, CA
Economic Values Environmental Values Social/Cultural Values
Direct Values 3.6 2.2 3.3
Indirect Values
2.7 3.6 0.2

Page 110
Conclusions

Even castles made from sand fall to the sea, eventually.
Jimi Hendrix

We are tied to the ocean. And when we go back to the sea, whether it is to sail or to
watch – we are going back from whence we came…
John F. Kennedy

Coastal areas have been centers of population growth and economic development for
centuries if not millennia. Coastal areas are exposed to a number of hazards, such as
erosion, flooding and wave attack, that can make coastal communities especially
vulnerable to disasters. With climate change and rising sea level, these hazards are
expected to worsen in the future. Hazard events such as storms, hurricanes or tsunamis
cannot be prevented, and communities are not likely to abandon all use of the coast.
Therefore ways to increase community resilience are needed.

Essential community infrastructure is often located in hazardous areas, and this is
especially true along the coast. Power plants, wastewater treatment plants, fuel supplies
and transportation facilities are four important elements of community infrastructure that
have high or moderate levels of interdependencies with other infrastructure, such that
they are important to the functioning of other infrastructure. These four elements of
community infrastructure also have important roles during post-disaster recovery. If a
coastal disaster were to interrupt these services, the loss can cause other services to also
go off-line and greatly delay the time for community recovery. However, in many coastal
communities, these facilities are located quite close to the coast and their losses during a
disaster can greatly reduce overall community resilience.

Over time, changes can be made to coastal infrastructure to reduce its vulnerability
through replacement or development redundant systems in less hazardous areas. The size
and exposure of some critical facilities can be reduced over time as new facilities replace
older ones and can be placed in a less hazardous location or as new technologies allow
for greater disaggregation of services. But, for the short to mid-term, communities will
need to develop or maintain protection programs that will ensure that these services can
be available throughout a disaster or restored quickly if there are interruptions due to the
hazard event.

Community resilience is important for all phases of a disaster, from the pre-disaster
preparations and the disaster through to the recovery and times of on-going activities.
Coastal protection features can be important for community resilience during the four
phases of a disaster. During the pre-disaster and disaster phases, the protection features
are important for protecting life and property from the event. During recovery and even

Page 111
times of on-going activities, functioning protective features will allow these activities to
proceed with some amount of protection from future hazard event; thus, it is important
that protective features survive an event or are able provide some protection even after
being damaged.

Past disasters can provide useful information about how various structures perform under
extreme or high load conditions. Field investigations can provide information on the
characteristics of an event that are most damaging, and the engineering aspects of
protective features that are most likely to remain functional or most likely to be damaged.
For example, scour and high water due to surge and waves were both observed to cause
damage during several recent coastal disasters, resulting in damage to structures that were
either not founded deeply enough to resist the scour or elevated high enough to avoid
wave impacts or overtopping.

Information from past disasters can help with refinement of extreme event modeling,
model validation, the development of codes and standards for safe design, and heightened
awareness of the range of events that are possible along the coast. Information from past
disasters can also provide general information on what works and what does not work
and the various types of resilience that can be provided by various protective features.
Information from past events has also helped develop and implement early warning
systems. Early warning systems during the pre-event phase can greatly reduce disaster
fatalities by providing people with time to either evacuate the community or go to a safer
location. In addition, flood sensitive equipment can be shut-down or put into safety
mode; property owners can protect buildings and tunnels from flooding with shutters,
sand bags, or flood barriers; and communities with surge or tsunami gates can activate
these structures. All these temporary protection measures are useful for resilience, but
they only work if there is information about an approaching event and sufficient time to
act upon this information.

Past disasters, however, cannot identify fully the risks and vulnerabilities of individual
communities. Such analysis, often undertaken as part of a study of community
vulnerability, requires detailed characteristics of local hazards, bathymetry and
topography and careful evaluation of the protective functions of all existing or proposed
natural and constructed protective features, and has not been the focus of this research.
Nevertheless, the disaster responses of protective features can provide guidance and
insight for community-scale vulnerability and risk analyses and many of the lessons
learned can be of benefit to all coastal communities.

The pre-disaster and disaster phases tend to dominate much of the discussion of
resilience; but, over years or even decades, communities spend the majority of time in
phases of recovery and on-going activities. Some of the characteristics of protective
features that make they useful during a disaster, such as height or deep embedment, may
be of little use during recovery and times of on-going activities. For the pre-disaster and

Page 112
disaster phase, useful information on resilience covers whether the protection provides
hard or soft resistance, whether it addresses flooding, erosion or wave impacts, what
protection might be possible if the structure fails, and what maintenance is needed to
sustain the protective function. During the recovery and on-going activities phases, useful
information on resilience covers the impacts and benefits from the protective features to
the community, and what are the economic, environmental and social/cultural
characteristics of the protective features.

Community resilience and protection comes from a large range of features. The major
features can be characterized as being natural elements, engineering structures, Building
protection, land use planning and miscellaneous protection. Natural elements include
such features as beaches and sand retention, wetlands, marshes and reefs. Engineered
structures include such features as seawalls, groins, jetties, revetments, large sand bags,
geotubes, and surge barriers. Building/structure-scale protection can include shutters,
storm barriers, small sand bags, inflatable barriers, pumps and flood-proof vaults. Land
use options can include setbacks, easements, lot acquisition, transfer of development
credit, and building codes. Finally, early warning systems for pre-event alerts and
insurance to fund post-disaster recovery are two other features that do not fit into any of
the other categories but that are important for community resilience.

A condensed list of key protective options has been reduced into the Coastal Community
Hazard Protection Resilience Index (CCHPR Index). The condensed list covers most of
the options that a community would consider for protection, without going into the
different techniques for achieving the protection. For example, there are many options for
developing and retaining a beach and these details are covered in the appendices for the
protection options. However,, the value to a community from the beach does not depend
upon how the beach was developed, so the condensed list of protection options discussed
beaches, regardless of sand source. Thus, the condensed list covers the key protective
features, enabling communities to compare them without concern for the implementation
details that will be more of a site-specific analysis.

The CCHRP Index provides information on how each protective feature functions for
disaster protection and the economic, environmental and social/cultural values that are
provided. Vastly different features are included in the CCHPR Index, providing broad
options for communities. The CCHPR Index provides a means to compare coastal
protection elements across several important community aspects that rarely have
intercomparable metrics – economical, environmental and social/cultural aspects. The
CCHPR Index does not depend upon scale, nor does it require a detailed assessment of
community vulnerability or evaluation of the condition of existing shore protection. The
assignment of high, medium and low ratings to the economic, environmental and
social/cultural benefits (or costs) of each type of protection provides a non-monetary

Page 113
comparison of options and a means to assess the current protective options that are
already in use by a community.

The CCHPR Index separates the values that derive from the protective features
themselves, from the secondary values of the community assets that are being protected.
While a community may decide that certain assets require different levels of protection
than other assets, due to their cost, environmental importance or social value, the features
provide protection and exhibits economic, environmental and social/cultural values
without regard for the inland assets.

The CCHRP Index enables communities to develop a first cut evaluation of the resilience
and values of their existing protective features. It will also enable communities to
evaluation of how the addition or deletion of various protective features will change the
various community values. The Ocean Beach shoreline of San Francisco, California, was
used as a test case to provide an example of how the CCHRP Index can be applied by a
coastal community. The existing conditions are evaluated, identifying the economic,
environmental, and social/cultural values for the shoreline protective features and the
inland assets that are being protected.

The application of the CCHRP Index to Ocean Beach shows that the different economic,
environmental, and social/cultural values capture different aspect of both the shore
protective features and the inland assets. It also shows the differences in direct values
from the protective feature and the secondary values from the inland assets. At this time,
Ocean Beach is the only community that has been evaluated with the CCHRP Index. As
more communities are evaluated, or as scenarios for the future of Ocean Beach evaluated,
there will be opportunities to develop a range of economic, environmental and
social/cultural values for multiple communities, compare communities to each other, and
evaluate the significance of the different values. As the CCHRP Index is applied to more
areas and as more values are developed, additional utility of the Index will become
apparent.

Page 114
Appendix A.

Table A-1 Coastal Protection Options – Technical Details 116 - 132
Table A-2 Coastal Protection Options – Effectiveness, Costs and
Failure Modes 133 - 150
Table A-3 Coastal Protection Options – Disaster Protection Values 151 - 159
Table A-4 Coastal Protection Options – Values During Recovery 160 - 163
Table A-5 Coastal Protection Options – Values During On-going
Activities 164 - 167

These Tables have been described in Chapter Five. They provide the foundation for the
CCHPR Index discussed in Chapter Six. Due to the length of each table, they have been
placed into this Appendix, rather than disrupt the continuity of the text.

Information in Tables A-1 through A-5 is based upon professional judgment, field
observations and a number of published reports, including:

Blankespoor, B., S. Dasgupta, and B. Laplante. 2012. Sea-Level Rise and Coastal
Wetlands: Impacts and Costs. The World Bank: Policy Research Working Paper 6277.

de Groot, R., L Brander, S. van der Ploeg, R. Costanza, F. Bernard, L. Braat,. M.
Christie, N. Crossman, A. Ghermendi, L Hein, S. Hueeain, P. Kumar, A. McVittie, R.
Portela, L.C. Rodriguez, P. ten Brink, and P. van Beukering. 2012. “Global estimates
of the value of ecosystems and their services in monetary units” Ecosystem Services
1(2012): 50 – 61.

Dijkman, J. (ed.). 2007. A Dutch Perspective on Coastal Louisiana Flood Risk
Reduction and Landscape Stabilization: Final Report. Neatherlands Water Partnership.
(ESA Monterey Bay 2012)

ESA PWA, 2012. Evaluation of Erosion Mitigation Alternatives for Southern
Monterey Bay, prepared for Monterey Bay Sanctuary Foundation and the Southern
Monterey Bay Coastal Erosion Work Group, 216 p.

ESA PWA, 2013. Analysis of the Costs and Benefits of Using Tidal Marsh
Restoration as a Sea Level Rise Adaptation Strategy in San Francisco Bay, prepared
for the Bay Institute,
http://thebayinstitute.blob.core.windows.net/assets/FINAL%20D211228.00%20Cost%
20and%20Benefits%20of%20Marshes%20022813.pdf; 67 pgs.

Fulton-Bennett, K, and G.B. Griggs, 1986. Coastal Protection Structures and Their
Effectiveness, joint publication of State of California Department of Boating and

Page 115
Waterways, and the Marine Science Institute of the University of California at Santa
Cruz, 50 p.

Hinkel, J. D. Lincke, A.T. Vafeidis, M. Perrette, R.J. Nicolls, R.S.J. Tol, B. Marzeion,
X. Fettweis, C. Ionescu, and A. Levermann. 2013. “Coastal flood damage and
adaptation costs under 21
st
century sea level rise” PNAS, Online Publication, doi:
10.1073/pnas.1222469111.

Hoozemans, Marchand, and Pennekamp.1993. A Global Vulnerability Assessment:
Vulnerability assessments for population, coastal wetlands and rice production on a
global scale. Second Revised Edition. Delft Hydraulics, The Netherlands.

Jonkman, S.N., M.M. Hillen, R.J. Nicholls, W. Kanning, and M. van Ledden. 2013.
“Costs of Adapting Coastal Defences to Sea-Level Rise – New Estimates and Their
Implications” Journal of Coastal Research 29(5): 1212 – 1226.

Personal Communication from Walt Crampton, PE, concerning California
construction costs.

Table A-1. Coastal Protection Options – Technical Details
Page 116

Table A-1. Coastal Protection Options – Technical Details
Technique
Details/
Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time
Beach Enhancement (Individual projects or part of a Regional Sediment Management Program)

Remove dams
to restore
sediment
transport by
river
Restore riverine
sediment supplies
Adds sediment to coast;
widens local beaches;
helps dissipate wave
energy -- Soft Resistance
Natural delivery of
sediment to the coast,
restoration of flood
variability and peak
flows
Dam removal is
expensive; can
result in lost water
storage and flood
reduction
Government,
Water agency,
NGO
Dam removal
can take several
years and may
need
environmental
review.

By-pass
sediment
around
reservoir and
dam
Restore riverine
sediment supplies
Adds sediment to coast;
widens local beaches;
helps dissipate wave
energy -- Soft Resistance
Return sediment into
downstream channel
By-passing may
require mechanical
transport if
downstream flows
are not sufficient to
carry sediment
Government,
Water agency,
NGO
Sediment
movement could
begin within
months of
initiation.

Harbor
dredging and
by-passing
Restore coastal
sediment supplies
Relocated littoral sand to
widens local beaches;
helps dissipate wave
energy -- Soft Resistance
Moves sediment from
harbors/ navigation
channels where it is a
hazard to where it can
enhance beach
shorelines
Dredging costs are
covered through
harbor
maintenance;
beach/nearshore
placement is a
small added cost
Government,
Harbor district
Harbor dredging
and by-passing
could take a
year or more to
initiate; once
started it could
continue at
regular intervals

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Technique
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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Canyon
interruptions
Prevent sand
losses into
submarine canyons
Hard structures are likely;
prevent loss of sediment to
offshore; widens local
beaches; helps dissipate
wave energy -- Soft
Resistance
Provides a source of
beach-compatible
sediment for
nourishment in back-
passing or by-passing
Untested
technology. Back-
passing requires
mechanical
transport. Canyon
head-cutting may
impact diversion
structures Government
Likely to take
several years for
first project;
possibly starting
as a pilot project

Nourish with
sand from
reservoirs or
debris basins
Adds sand to
beaches or littoral
cells to widen the
beach
Adds sediment to coast;
widens local beaches;
helps dissipate wave
energy -- Soft Resistance
Provides recreational
beach area, enlarges
beach habitat and
backshore protection.
Benefits generally
proportional to sand
volume
Reservoirs and
debris basins
benefit from clean-
out; nourishment
costs associated
with sediment
screening and
transport. Only
advantageous if
large % of
sediment is sand.
Government,
Water agency
Several months
to find sand
sources, test for
beach quality
and initiate
transport.

Nourishment
with offshore
sand
Adds sand to
beaches or littoral
cells to widen the
beach
Adds sediment to coast;
widens local beaches;
helps dissipate wave
energy -- Soft Resistance
Provides recreational
beach area, enlarges
beach habitat and
backshore protection.
Benefits generally
proportional to sand
volume
Dredging costs
included in beach
nourishment.
Mobilization and
demobilization
costs ~$1 million
US in addition to
sand costs.
Government,
private groups
A year or more
for permitting
and to complete
project plans

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Structure
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Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Nourish with
coarser than
native sand
Adds sand to
beaches or littoral
cells to widen the
beach
Adds sand to coast;
widens local beaches;
helps dissipate wave
energy; coarser grains
more resistant to erosion --
Soft Resistance
Provides recreational
beach area, enlarge
beach habitat and
backshore protection.
Coarser sand will remain
longer on the beach.
Benefits generally
proportional to sand
volume
Costs based on
sand sources.
Dredging or inland
quarry sites.
Coarser sand may
be no more costly
than native sand.
Government,
private groups
Timing would
depend upon
sand source.
Inland sources
might be faster
than offshore
sand.

Nourish with
crushed glass
Add rounded glass
particles to the
beach or littoral cell
to widen the beach
Adds sand to coast;
widens local beaches;
helps dissipate wave
energy; possibly more
resistant to erosion if
grains are coarser than
native sand -- Soft
Resistance
Increases sand volume
to widen the beach area.
Glass can be an
expensive but
durable source of
sand.
Government,
private groups
A month or two
to initiate.

Retain Sand Material

Sand
Backpassing
Move sand from a
downcoast section
of beach to an
upcoast section
Relocates sand to widen
targeted beach sections;
helps dissipate wave
energy -- Soft Resistance
Keeps sand in littoral cell
longer than it would stay
normally
Needs trucks or
pumps to move
sand upcoast.
Reduces
downcoast
transport of sand
Government,
private groups
A month or two
to initiate, but
timing might be
seasonal to be
most effective.

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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time
Beach berms
Move sand from
lower beach into
backshore berms
for back shore flood
and erosion
protection
Relocates beach sand;
heightens back beach
elevation to reduce inland
wave run-up -- Soft
resistance
Reduces early season
cross-shore losses of
sand; provides
backshore elevation to
block waves and
flooding
Small impacts due
to disturbances
from redistribution
of sand; impacts
occur each time the
berms are built or
rebuilt
Government,
local property
associations
or districts
Rapid; can be
installed in a few
days or a week.
Maintenance
can take a day
or two.
Groins
Structures
perpendicular to
longshore transport
to prevent or
reduce sand loss;
projects often
include pre-fill to
reduce downcoast
impacts
Hard Structures; can be
used to retain beach sand
on upcoast beach; can
augment or enhance
beach nourishment -- Soft
Resistance
Holds sand and widen
beach area upcoast of
groin to reduce erosion
and inland flooding
Groin structures
compartmentalize
the beach; can
interfere with beach
access. Downcoast
erosion can be
reduced by pre-
filling cells.
Government,
port districts,
local property
associations
or districts;
occasionally
single land
owners
Normally multi-
year for studies
and permits.
Construction
can take several
months
Jetties
Inlet stabilization;
placed up and/or
downcoast of a
river, estuary,
navigation channel
or harbor to
maintain tidal
action; usually
perpendicular to
shoreline
Hard Structures; prevents
beach erosion from
migration of river thalweg;
Can retain beach sand on
upcoast beach.
Navigational aid or
habitat aid for estuaries
that close intermittently.
Can also function like a
groin to hold sand
upcoast of inlet.
Jetty can interrupt
longshore sediment
transport.
Downcoast erosion
may result; pre-
filling the ebb tidal
delta may reduce
erosion.
Government,
port districts,
Conservation
agencies
Estuary
restoration
proponents
Normally multi-
year for studies
and permits.
Construction
can take one to
two years.

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Structure
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Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Perched
beach
Install a sill to
maintain a beach
area inland of the
sill without
nourishing the full
profile
Hard Structures; retain
sand inland of sill; helps
dissipate wave energy --
Soft Resistance
Provides beach area
without the volumes of
sand needed for full
profile nourishment; can
protect offshore hard
bottom resources
Step-off from sill
can be dangerous;
perched beach
sand will not be
cleaned by tidal
and wave flushing Government
Normally multi-
year for studies
and permits.

Breakwaters-
submerged
Submerged
breakwaters reduce
wave energy inland
of the breakwater.
Need to be wider
than emergent
breakwaters to be
effective. They can
be used to enhance
beach build-up,
provide safe area
for boat anchorage
or navigation.
Hard Structures; cause
waves to break away from
beach and inland areas;
reduce wave energy --
Soft Resistance
Reduces wave energy in
the lee of the structure
will cause sediment
deposition and beach
widening behind and
upcoast of the structure.
Can provide hard rock
habitat and possible surf
recreation.
Covers existing
offshore habitat
with rocks or
caissons.
Breakwater can
interrupt longshore
sediment transport.
Downcoast erosion
may result.
Pre-filling may
reduce erosion
effects.
Government,
port or harbor
district,
conservation
agency to
create habitat
Normally multi-
year for studies
and permits.

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Structure
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Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Breakwaters -
emergent
Emergent or visible
breakwaters reduce
or block wave
energy inland of the
breakwater. They
can be used to
enhance beach
build-up, provide
safe area for boat
anchorage or
navigation.
Hard Structures; cause
waves to break away from
beach and inland areas;
reduce wave energy --
Soft Resistance
Reduces wave energy in
the lee of the structure
will cause sediment
deposition and beach
widening behind and
upcoast of the structure.
Need less space than
submerged breakwaters.
Can provide hard rock
habitat.
Covers existing
offshore habitat
with rocks or
caissons.
Breakwater can
interrupt longshore
sediment transport.
Downcoast erosion
may result. If
placed too close to
the shoreline, a
tombolo may
develop that will be
a full barrier to
sediment transport.
Government,
port or harbor
district.
Normally multi-
year for studies
and permits.

Breakwaters -
floating
Floating
breakwaters are
used to provide a
temporary safe
area for boat
anchorage or
navigation.
Rigid structures; dampen
short period waves;
reduce wave energy --
Soft Resistance
Reduces short-period
waves to provide calmer
water.
Limited changes to
sediment transport.
Impacts to offshore
bottom from
anchors.
Government,
port or harbor
district
Several months,
depending upon
anchorage
needs.

Delta
augmentation
Experimental
method to enhance
the shore
protection provided
by offshore deltas
at river mouths and
headlands.
Augment with cobble or
rocks; cause waves to
break away from beach
and inland areas; reduce
wave energy -- Soft
resistance
Works with an existing
delta; causes more
waves to shoal on the
delta, reducing inland
wave energy
May disturb
existing delta
habitat
Government,
conservation
agency
Normally multi-
year for studies
and permits.

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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Artificial
headland
Experimental
method to enhance
the sediment
retention upcoast of
a headland barrier.
Hard Structures; can be
used to retain beach sand
on upcoast beach; can
augment or enhance
beach nourishment -- Soft
Resistance
Works with an existing
headland to hold sand
and widen beach area
upcoast of headland to
reduce erosion and
inland flooding
May increase
downcoast erosion
if headland allows a
large volume of
sediment to pass.
Government,
conservation
agency
Normally multi-
year for studies
and permits.

Beach
dewatering -
active
Modify beach
permeability to hold
more sand on the
beach through
direct pumping and
draw down of
beach water.
Passive method is
experimental to
modify beach
permeability to hold
more sand on the
beach with
drainage pipes
Buried Structures; can be
used to retain beach sand;
can augment or enhance
beach nourishment -- Soft
Resistance
Holds more sand on the
beach, increases beach
width. Has limited beach
expansion value. Likely
to be a side benefit or
shallow beach wells.
Passive system has
shown short-term
benefits, but no long-
term beach changes.
Disturbance of the
beach to install
wells; energy costs
to maintain
pumping; some
energy costs may
be attributed to
water extraction;
passive system can
result in debris on
beach if drainage is
scoured by wave
energy.
Government,
water agency,
local property
owners
Normally multi-
year for studies
and permits.

Habitat protection

Wetland,
marsh or
mangrove
protection and
enhancement
Expands wetland,
marsh or mangrove
areas or improves
existing ecosystem
function
Wetlands, marshes and
mangroves maintain
elevated bedforms that
cause shoaling; root
structure and vegetation
provides roughness that
dissipates wave energy --
Soft Resistance
Provides high
environmental value by
enhancing fisheries
habitat, maintaining
water quality; and
reducing erosion.
Supports recreational
fishing
Space for wetland,
marsh or
mangrove;
equipment for
grading; plants for
habitat structure
Government;
conservation
agency, port
and harbor
districts, NGO
Normally multi-
year for studies
and permits;
maintenance of
existing habitat
can be
immediate

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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Dune
enhancement
Expands dune
areas or improves
existing dune
function; possible
internal core of rock
for added
protection
Heightened back beach
elevation reduces inland
wave run-up; vegetation
retains sand and provides
roughness to dissipate
wave energy -- Soft
resistance
Improves ecosystem
value; increases vertical
structure on the beach
Needs beach
space for dune
development;
requires sand to
build up dune area
and possibly rock
for interior core.
Government,
property
owner groups,
conservation
agency A few months

Multi-purpose
Reef
Add or enhance
offshore rocky
habitat; enhance
surfing
Hard Structures; cause
waves to break away from
beach and inland areas;
reduce wave energy --
Soft Resistance
Habitat improvements
for fisheries; increase
vertical structure in the
nearshore; significant
environmental and
social/cultural value
Will convert ocean
bottom to
alternative use;
rocks for reef
structure
Government,
wildlife agency
Normally multi-
year for studies
and permits;
maintenance of
existing habitat
can be
immediate
Habitat buffers
Provide space for
habitat to migrate;
keeps a buffer
between habitat
and development
Provide area for habitat to
adjust to sea level rise;
dissipates wave energy --
Soft Resistance
Habitat improvements;
value based on habitat
being protected
Removes
development
potential from land;
loss of tax base
Government,
conservation
agency,
wildlife group Immediate

Living
shorelines
Expands vegetation
areas along the
shore or improves
existing vegetation
function
Hazard avoidance;
increase wave dissipation
to protect inland
properties; accommodate
erosion -- Soft Resistance Habitat improvements
Land for shoreline
expansion, rocks
for protective sill,
plantings
Government,
property
owner group,
conservation
agency,
wildlife group Months to a year

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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time
Engineered Protection
Levees
Sloped or vertical
walls to block wave
impacts or flood
waters
Hard Structures; block
wave energy and flood
levels to height of levee --
Hard Resistance
Provides protection from
waves and flooding up to
levee height
Structure will
encroach onto
beach or floodplain;
can encourage
development in
hazardous
locations
Government,
property
owner group,
flood control
district
Multi-year for
studies and
construction

Horizontal
Levees
Broad vegetated
strip next to a levee
to reduce water
velocity and waves;
vegetation reduces
levee height
Hard Structures; dissipate
wave energy so vertical
structure blocks less wave
energy; blocks flood levels
to height of vertical wall –
Soft & Hard Resistance
Enhances habitat as part
of storm protection
Structure will
encroach onto
beach or floodplain;
can cause end
effects to untreated
shoreline;
can encourage
development in
hazardous
locations; costs for
land, rock for
protective sill,
plantings, levee
material
Government,
property
owner group,
flood control
district
Multi-year for
studies and
construction

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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time
Revetments
Rock slopes on a
beach or against a
bluff to protect from
waves and erosion
Hard Structures; dissipate
wave energy; block
erosion; rely upon rock
density, interlocking and
gravity for stability --Hard
Resistance
Provides protection from
erosion and storm
damage
Structure will
encroach onto
beach or floodplain;
cause end effects
to untreated
shoreline; beach or
wetland in front of
beach will continue
to narrow and
erode; can
encourage
development in
hazardous
locations
Property
owner, owner
group
One to two
years

Dynamic
Revetment
Add or enhance
rock, cobble, or
woody debris on
shoreline to reduce
backshore erosion
Hard Structures; increase
wave dissipation to protect
inland properties;
accommodate erosion --
Soft Resistance
Reduces erosion with a
flexible structure;
incorporates native
materials
Rocks, cobble or
large woody debris
for structure
Government,
property
owner groups,
conservation
agency
One year or
more for studies
and permits

Vertical tie-
back walls
Walls immediately
in front of coastal
bluffs to protect
from waves and
erosion
Hard Structures; block
wave energy and erosion;
relies upon back bluff for
stability -- Hard Resistance
Provides protection from
erosion
Structure will
encroach onto
beach; cause end
effects to untreated
shoreline; can
encourage
development in
hazardous location;
beach or wetland in
front of beach will
continue to narrow
and erode
Property
owner, owner
group
One to two
years

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Details/
Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time
Gravity walls
Walls on beaches
or in front of coastal
bluffs to protect
from waves and
erosion
Walls rely upon
massive foundation
and gravity to stay
in place.
Hard Structures; rely upon
structural bulk and gravity
for stability; can be built
incrementally, in segments
-- Hard Resistance
Provides protection from
erosion and storm
damage
Structure has a
large footprint that
will encroach onto
beach; beach or
wetland in front of
beach will continue
to narrow and
erode; cause end
effects to untreated
shoreline; can
encourage
development in
hazardous
locations
Property
owner, owner
group
One to two
years

Cantilever
walls
Walls on beaches
or that front coastal
bluffs for waves
and erosion.
Foundation is
cantilevered into
the ground for wall
stability.
Hard Structures; rely upon
embedment depth for
stability -- Hard Resistance
Provides protection from
erosion
Structure will
encroach onto
beach or floodplain;
beach or wetland in
front of wall will
continue to narrow
and erode; can
cause end effects
to untreated
shoreline
Property
owner, owner
group
One to two
years

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Details/
Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time
Sand Bags
Bags can be
installed
permanently or
deployed for
specific events;
stacks of sand
bags on beaches or
in front of coastal
bluffs to protect
from waves and
erosion
Reduce erosion, block
wave energy; structures
rely upon bag weigh,
interlocking and gravity for
stability -- Hard Resistance
Provides protection from
erosion and storm
damage
Structure will
encroach onto
beach or floodplain;
may cause end
effects to untreated
shoreline
Property
owner group,
flood control
district Days to weeks
Surge Barriers
Large gates across
a river mouth or
other flow
restrictions that
normally allow ship
passage and tidal
flows; close to
protect from waves
and inland flooding
Hard Structures, barriers
shut to provide protection;
rely upon structural bulk
and interconnections for
stability -- Hard resistance
Provides protection from
waves and flooding up to
height of barrier
May divert waves
and energy to
adjacent,
unprotected areas;
cause end effects
to untreated
shoreline; one-off
designs require
detailed design and
engineering; can
encourage
development in
hazardous
locations
Government,
flood control
district
Multi-year for
studies and
construction

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Details/
Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time
Building Protection
Setbacks
Locates
development inland
of some feature,
such as an eroding
bluff or floodplain,
to protect the
development
Hazard Avoidance;
accommodates erosion;
effectiveness declines as
site erodes -- Soft
Resistance
Provides erosion
protection without hard
structures; does not
encourage additional
development in
hazardous locations
Protection
decreases as site
erodes
Property
owner, owner
group
As part of new
development
projects
Elevation
Puts development
higher than
expected flood
level to protect from
water damage
Hazard Avoidance;
accommodates flooding;
effectiveness reduces as
sea level rises -- Soft
Resistance
Flood protection, up to
height of building
elevation
Change visual
character of area;
can encourage
development in
hazardous
locations
Property
owner, owner
group
As part of new
development
projects
Sand Bags
Provide flood
barriers on a
temporary basis for
buildings, or for a
few years, if used
to elevate existing
flood protection or
reduce erosion
Block wave energy and
flood waters; structures
rely upon bag weigh,
interlocking and gravity for
stability -- Hard Resistance
Protection from erosion
and flooding; can be
removed or stored off
site when not needed
Change visual
character of area;
need to be
maintained or
replaced if intended
for use over several
years; often not
fully removed once
they are no longer
needed
Property
owner, owner
group, flood
district
Hours to days to
deploy

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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Storm
Shutters
Cover windows,
doors, vents and
other entrances to
buildings to keep
floodwaters from
entering
Block wave energy and
flood waters; rely upon
attachment to structure for
stability -- Hard Resistance
Protection from waves
and flooding;
internalized costs
Usually requires
action on the part
of the property
owner to deploy the
storm shutters
Property
owner, owner
group
As part of new
development
projects; several
weeks to retrofit
buildings; hours
to deploy

Floodproof
Vaults
Keep equipment or
other items that can
be damaged by
water from
exposure to
floodwater
Surround item and block
flood water from entering -
- Hard Resistance
Protection from waves
and flooding;
internalized costs;
hastens recovery, if
equipment can return to
service without needing
repairs
May inconvenience
day-to-day
activities if vault
needs to be
opened regularly to
access equipment
Property
owner, owner
group
Days to months,
depending on
vault size
Pumps
Remove water
inland of barriers or
from lands below
water level, such as
basements Remove flood waters
Removes water before it
can reach a critical
threshold; hastens
recovery by removing
flood waters
Need to be kept in
working order so
they will function
when deployed
Government,
property
owner, owner
group
Days to months,
depending on
pump size;
minutes to
deploy
Storm Barriers
Close off opening
to tunnels,
subways, and other
underground items
Block wave energy and
flood waters; rely upon
attachment to structure for
stability -- Hard Resistance
Prevent or reduce flood
waters from entering
structures or facilities
Need to be kept in
working order so
they will function
when deployed;
may inconvenience
day-to-day
activities, if not
well-integrated into
overall design
Property
owner, owner
group
Months to a year
to install,
minutes to hours
to deploy

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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Building
Codes
Provide minimum
requirements for
new or renovated
buildings to
address life and
safety concerns.
Hazard Avoidance and
Resistance
Establishes design and
safe standards for new
development or
substantial
improvements; possible
small increase to tax
base
Add costs to
development;
codes include
economic criteria in
setting safety
levels; may
encourage
development in
hazardous
locations Government
Project-by-
project; Routine
with building
permits
Land Use/land acquisition options

Fee simple
purchase of
land
Takes private land
off the market
through purchase
of property
Hazard Avoidance; keep
development away from
high hazard areas
Removes development
from risk; does not
encourage additional
development in
hazardous locations;
land can be used for
open space or
conservation
High financial cost
for land; removes
development
potential from land;
loss of tax base
Government,
NGOs,
Conservation
Agencies
Fairly quickly, if
funds are
available and
there is a willing
seller

Conservation
Easements
Puts land into
conservation use
Hazard Avoidance; move
development away from
high hazard areas
Provides land for
conservation
management; does not
encourage additional
development in
hazardous locations
Can be required as
part of approval for
development; loss
of tax base
Government,
Conservation
Agencies,
NGOs
Quickly, once
program is
established

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Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time

Transfer of
Development
Credits
Moves
development
potential from
hazard areas to
safer locations
Hazard Avoidance; keep
development away from
high hazard areas
Retires development
potential for hazardous
sites; transfers it to safer
sites; land can be used
for open space; loss of
tax base can be off-set
by tax on transfer land
Requires a
program to identify
sites for changes to
development level;
removes
development
potential from land
Government,
land trusts,
NGOs
Quickly, once
program is
established

Managed
Retreat
Moves or relocates
development out of
harms' way.
Hazard Avoidance; move
development away from
high hazard areas
Removes portions of
development as they
become at risk; useful
for risk from erosion;
accommodates
development; does not
encourage additional
development in
hazardous locations
Property owner is
responsible for
removal of
development as it
is threatened;
gradual reduction in
tax base
Government,
Land Trust,
NGOs
Quickly, once
program is
established

Rolling
Easements
Moves public or
conservation
easements inland
with some land
change
Hazard Avoidance; move
development away from
high hazard areas
Removes portions of
development as
resources or resource
triggers encroach on
development area; does
not encourage additional
development in
hazardous locations
Property owner is
responsible for
removal of
development as
resource trigger
encroaches;
gradual reduction in
tax base
Government,
land trusts,
NGOs
Quickly, once
program is
established

Table A-1. Coastal Protection Options – Technical Details
Page 132
Technique
Details/
Structure
Details
Options for use Protection Method Benefits Impacts Acting Party
(Normal)
Implementation
Time
Miscellaneous
Insurance
Provide money to
repair or replace
damaged
structures Financial compensation
Hastens opportunity for
recovery; may indirectly
reduce damages if
insurance is tied to
building improvements
Costs depend upon
value of insured
property; insurance
may promote
development in
high hazard areas
that might
otherwise not
occur.
Insurance and
reinsurance
companies,
government,
communities,
and property
owners
Quickly, once
program is
established; can
take months for
payment.

Early Warning
Systems
Alert communities
to potential or
imminent hazards
Provide time to evacuate
high hazard areas;
possibly time to secure
property and equipment
Saves lives; hastens
recovery if equipment
and property can be
protected prior to event
Systems need to
include detection,
tracking and
projections or
modeling of
landfall; costs can
be high; involves
multiple
communities to
cover costs; may
promote
development in
high hazard areas
that might
otherwise not
occur.
Government,
NGOs
Several years to
establish a fully
implemented
system; minutes
to deploy.

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 133
Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes
Beach Enhancement (Individual projects or part of a Regional Sediment Management Program)

Remove Dams
to restore
sediment
transport by
river
Benefits to the
watershed and
beach area near
river mouth and
littoral cell
Effective as long
as sediment
transport
continues,
depends upon
volume of sand
placed on beach
Decrease over
time, unless
sediment volume
conveyed to the
river increases
High -- some costs could be
attributable to dam safety or
habitat restoration Low
Riverine flooding
due to dam
removal; excess
streambed
sedimentation.
Failure mode at
beach is erosion

By-pass
sediment
around
reservoir and
dam
Benefits to beach
area near river
mouth or
placement site
and littoral cell
Effective as long
as sediment
transport
continues,
depends upon
volume of sand
placed on beach
Decrease over
time, unless
sediment volume
conveyed to the
river increases
High -- some costs could be
attributable to dam safety or
reservoir maintenance Moderate to high
Excess streambed
sedimentation.
Failure mode at
beach is erosion

Harbor
dredging and
by-passing
Benefits to beach
area near
placement site
and littoral cell
Effective as long
as sediment
transport
continues,
depends upon
volume of sand
placed on beach
Decrease over
time, unless
sediment volume
in the harbor
increases
Moderate to high -- some
costs could be attributed to
harbor maintenance
Moderate to high --
maintenance is the
continued dredging
and by-pass effort
Failure mode at
beach is erosion

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 134
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Canyon
interruptions
Beaches
downcoast of
canyon or at
within littoral cell
Effective as long
as sediment
transport
continues,
depends upon
volume of sand
placed on beach
Decrease over
time, unless
volume increases
High -- untested technology;
all costs attributable to
beach nourishment effort
Possibly high -- but
uncertain
Collapse of
interrupter;
sediment goes into
canyon

Nourish with
sand from
reservoirs or
debris basins
Beach area at
placement site,
and littoral cell.
Effective as long
as sediment
transport
continues,
depends upon
volume of sand
placed on beach
Decrease over
time, unless
volume increases
Moderate -- debris basin
and reservoir clean up
would be needed separately
from the placement of sand
on the beach
Low to Moderate --
similar to initial
costs
Failure mode at
beach is erosion

Nourishment
with offshore
sand
Beach area at
placement site,
and littoral cell
Temporal
effectiveness
depends upon
volume;
normally
projects
designed to be
effective for
several years
Decrease over
time, unless
volume increases
High -- all costs attributable
to beach nourishment effort;
dredge mobilization about
$1 - 1.5 M per project;
without dredging costs,
sand costs about $5 to
10.50/ cu m, in the US. Low to none
Failure mode at
beach is erosion

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 135
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Nourish with
coarser than
native sand
Beach area at
placement site,
and littoral cell
Temporal
effectiveness
depends upon
volume;
normally
projects
designed to be
effective for
several years
Decrease over
time, unless
volume increases
High -- all costs attributable
to beach nourishment effort;
dredge mobilization about
$1 - 1.5 M per project
without dredging costs,
sand costs about $5 to
10.50/ cu m, in the US. Low to none
Failure mode at
beach is erosion

Nourish with
crushed glass
Beach area at
placement site,
and littoral cell
Temporal
effectiveness
depends upon
volume;
normally
projects
designed to be
effective for
several years
Decrease over
time, unless
volume increases
Moderate -- all costs
attributable to beach
nourishment effort; high
costs for sand and trucking
but no dredging costs. Low to none
Failure mode at
beach is erosion

Retain Sand Material

Sand
Backpassing
Beach area at
placement site,
and littoral cell
One or two
years unless
additional sand
in brought into
the system
Decreases over
time unless
volume increases
Moderate -- some costs
may be covered for
reservoir maintenance
Low to Moderate --
if backpassing is
on-going
Failure mode at
beach is erosion

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 136
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes
Beach berms
Limited to length
of berm
Time that the
berm is in place;
often used for
seasonal
protection, and
rebuilt annually
Berm height and
foundation may
need to increase
as sea level rises
Low -- often berms can be
built by public works
department with existing
equipment
Possible additions
of more sand
throughout the
season. Post-storm
redistribution of
sand can be by
waves or
mechanized
equipment
Erosion, slumping,
or breaching of the
berms leading to
greater
overtopping or
inland flooding
through gaps in
the berm if
drainage is not
part of design,
berms can cause
inland flooding
Groins
Sand retention
can extend far
upcoast; depends
upon shoreline
orientation, groin
length, groin
spacing, and
transport. Many years
Reduced
effectiveness with
rising sea level;
will vary with initial
groin height; groins
may need to be
rebuilt or
foundation
enlarged to match
changing water
levels
High -- costs about $14 to
$22 M/km of protection;
$17 to $26 M/km including
sand placement
Moderate to high --
possible need to
restack rocks or
armor units is
structure is
damaged by storm
waves; costs about
2 to 5% initial
costs, plus $2 to 3
M/km every 5 to 10
years for sand
Loss of elevation,
scattering of rock,
unraveling at the
head leading to
diminished
effectiveness and
beach erosion

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 137
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes
Jetties
Sand retention
can extend far
upcoast; depends
upon shoreline
orientation, jetty
length and
transport. Many years
Changes in
effectiveness will
depend upon
changes to
shoreline position
and changes to
inland flows.
Jetties may need
to be rebuilt or
enlarged to match
changes in water
level; foundation
may need to be
widened
High -- depend upon length
and wave climate
Channel dredging
and possible need
to restack rocks or
armor units if
structure is
damaged by storm
waves
Loss of elevation,
unraveling at the
head, scattering of
rock along the
trunk leading to
increased porosity,
sedimentation and
higher currents in
the channel
Perched beach
Limited to length
of sill and perched
beach area
A few years to a
decade; will
need periodic
sand cleaning
and
renourishment
Effectiveness will
lessen with rising
water levels unless
sill is heightened
and widened to
match changes in
water level
Moderate to high -- $4 to
4.6 M/km, assuming sill
costs 25% of revetment cost
and beach is 20 sq m/m at
$5 to 6/cu.m.
Will need periodic
sand cleaning and
nourishment. Sill
may be damaged
by storm waves
Scattering of
rocks, loss of sill
elevation; removal
of sand inland of
sill; reduced beach
and water quality,
since beach is not
flushed by wave
action

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 138
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Breakwaters-
submerged
Sand retention
can extend far
upcoast; depends
upon shoreline
orientation,
breakwater length,
distance from
shore, spacing
between
structures, and
transport. Many years
Reduced
effectiveness with
rising sea level;
will vary with initial
breakwater
dimensions;
breakwater height
and foundation
width may need to
be enlarged to
remain effective
with changing
water level
High -- $26 to 42 M/km of
shore protection for
structure;
$31 to 47 M/km with
structure and sand
placement; based on costs
for emergent breakwater
with 25% increase in
structure costs due to
increased material needed
Small -- may need
increased elevation
to match rising
water levels
Loss of elevation,
unraveling at
ends, scattering of
rock along the
trunk leading to
less reduction in
wave heights or
wave energy
inland of structure;
less beach
retention

Breakwaters -
emergent
Sand retention
can extend far
upcoast; depends
upon shoreline
orientation,
breakwater length,
distance from
shore, spacing
between
structures, and
transport Many years
Reduced
effectiveness with
rising sea level;
will vary with initial
breakwater width
and height;
breakwater height
and foundation
width may need to
be enlarged to
remain effective
with changing
water level
High -- $21 to 34 M/km of
shore protection for
structure;
$26 to 39 M/km with
structure and sand
placement
Moderate -- can be
5 to 10% of initial
cost; added cost to
elevate structure to
match rising water
levels
Loss of elevation
and eventual
submersion,
unraveling at
ends, scattering of
rock along the
trunk leading to
less reduction in
wave heights or
wave energy
inland of structure;
less beach
retention

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 139
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Breakwaters -
floating
At the immediate
area of the
structure
A few years to a
decade; not
intended for
long-term use
Effectiveness will
not change with
rising sea level
Moderate -- actual costs not
available
Moderate to High --
likely to be 10 to
15% of initial cost
Break away from
anchors; tear or
breach in floating
cells; complete
loss of wave
protection

Delta
augmentation
Sand retention
can extend inland
of delta as well as
upcoast
Many years, or
until delta
deteriorates
Reduced
effectiveness with
rising sea level;
will vary with initial
delta size; delta
may need to be
enlarged to remain
effective with
changing water
level
Assumed to be moderate --
but there have not been any
projects to determine actual
costs
Small to Moderate
-- possible to add
more material to
delta every 10 to
15 years
Loss of delta
elevation,
scattering of rocks
throughout
offshore area;
reduced sand
retention

Artificial
headland
Sand retention
can extend
upcoast of
headland
Many years, or
until delta
deteriorates
Reduced
effectiveness with
rising sea level;
will vary with initial
height. Headland
may need to be
rebuilt or enlarged
to match changing
water levels
Assumed to be Moderate --
costs likely to compare with
those of a single groin -- $1
to 5 M.
Small to Moderate
-- 5 to 10% of initial
cost
Loss of headland,
reduced or total
loss of sand
retention

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 140
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Beach
dewatering -
active or
passive
Immediate area of
dewatering;
possible upcoast
retention if
accreted beach
reduces longshore
transport; overall
effectiveness from
passive system is
unproven
As long as the
dewatering is
active; long-term
effectiveness of
passive system
is unproven
Effectiveness will
not change with
rising sea level if
pumping structures
can be elevated to
match water level
Assumed to be moderate to
low -- system costs not
available
Moderate to High --
continued demand
for energy for
active system;
long-term viability
of passive system
is unproven
Erosion of beach,
loss of pumping
structures to
erosion

Habitat protection

Wetland, marsh
or mangrove
protection and
enhancement
Area inland of
wetland, marsh or
mangrove area.
Some benefits
may extend
slightly beyond
inland projection
of habitat area
As long as the
wetland, marsh
or mangrove
remains in place
Effectiveness may
not change with
rising sea level if
there is sufficient
sediment and time
for vertical
structure to
aggrade High -- up to $40,500/ha $18,900/ha
Die-off of
vegetation, loss of
elevation so
vegetation drowns

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 141
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Dune
enhancement
Area inland of
dunes
As long as the
dune remains in
place
Effectiveness likely
to drop, unless
dune height is
supported by
inland sand
accretion, possibly
through profile shift
and the Bruun rule High -- about $6.8 M/km
Regular additions
of sand if dune is
not nourished
naturally be the
fronting beach
Erosion, slumping,
or breaching of the
dunes leading to
greater
overtopping or
inland flooding
through gaps in
the dune. An
armored core may
protect against
major dune
collapse

Multi-purpose
Reef
Area inland of
reef. Some
benefits may
extend slightly
beyond inland
projection of the
reef
As long as the
reef remains in
place
Effectiveness likely
to drop unless reef
height grows due
to additional
marine growth
Very high -- $21 to 34 M/km
of shore protection for
structure;
$26 to 39 M/km with
structure and sand
placement
Some addition of
hard material may
be needed to
maintain reef
profile or provide
additional height to
keep pace with sea
level rise
Loss of elevation,
unraveling at ends
and scattering of
rock along the
reef; larger wave
heights and higher
wave energy
inland of structure;
and less beach
retention
Habitat buffers Area of the buffer
As long as the
buffer remains
Effectiveness likely
to drop with
climate change as
habitat moves into
buffer Depends on land costs
Small -- keep area
open for habitat
migration
Loss of land to
development

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 142
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Living
shorelines
Vegetated banks
inland of
shoreline. Some
benefits may
extend slightly
beyond inland
projection of the
living shoreline, if
shoreline end is
tapered into
untreated
shoreline
As long as living
shoreline
remains in place
Effectiveness likely
to drop with
climate change, as
living shoreline
erodes, or is
inundated
Moderate to high -- $4.2 to 5
M/km, assumes sill costs
25% of revetment cost and
vegetation is 10 meters
wide at $4/sq. m.
Low to Moderate --
maintain sill and
plantings following
high velocity
events that might
disturb plant
stability
Collapse of sill,
loss or inundation
of vegetation

Engineered Protection
Levees
Area enclosed by
levee
No temporal
constraint, as
long as levees
are maintained
Will decrease with
rising sea level rise
and increased
storminess; levee
height and
foundation width
may need to be
increased to match
water level
High to very high -- depends
upon height, material and
land costs;
T-walls about $6.5 to 16
M/km;
clay covered about $5
M/km;
stone covered about $9 to
17 $M/km, including
maintenance
Moderate --
average annual
costs estimated to
be 1% of initial
costs; r
aising and
strengthening
costs similar to
initial construction
Collapse, breach,
loss of elevation,
slumping of side
walls

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 143
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Horizontal
Levees
Area inland of the
revetment.
Possible end
erosion unless
revetment is
carefully tapered
into untreated
shoreline
No temporal
constraint, as
long as levees
are maintained
Will decrease with
rising sea level rise
and increased
storminess; levee
height and
foundation width
may need to be
increased to match
water level
High -- $4 to 4.2 M/km,
Including tidal or brackish
marsh creation
Moderate -- likely
comparable to
revetment costs;
average annual
costs about 5% of
initial costs
Collapse, breach,
loss of elevation,
slumping of side
walls, loss of
vegetation and
resulting wave
dissipation
Revetments
Area inland of the
revetment.
Possible end
erosion unless
vegetation is
carefully tapered
into untreated
shoreline or
unmodified levee
No temporal
constraint, as
long as
revetment is
maintained
Will decrease with
rising sea level rise
and increased
storminess;
revetment height
and foundation
width may need to
be increased to
match water level Very high -- $15 to 18 M.km
Moderate -- annual
costs about 5 to
10% of initial costs
Loss of elevation
and scattering of
rock along the
shoreline, leading
to greater
overtopping,
erosion and
flooding

Dynamic
Revetment
Area inland of the
revetment.
Possible end
erosion unless
revetment is
carefully tapered
into untreated
shoreline
No temporal
constraint, as
long as
revetments are
maintained
Will decrease with
rising sea level rise
and increased
storminess;
revetment height
and foundation
width may need to
be increased to
match water level
High -- $7 to 10 M/km,
based on revetment costs;
assumes revetment can use
some native materials
Moderate -- slightly
more than a
conventional
revetment; average
annual costs about
10 to 15% of initial
costs
Loss of elevation,
scattering of rock
along the
shoreline, leading
to greater
overtopping, and
inland erosion and
possible flooding

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 144
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Vertical tie-back
walls
Area inland of the
vertical wall.
Possible end
erosion unless
wall is carefully
tapered into
untreated
shoreline
Tie-backs will
slowly lose
tension over
time; may
require tieback
replacements
after about 30 to
40 years
Effectiveness likely
to drop with
climate change;
wall height and
foundation width
may need to
increase to keep
pace with water
level.
High -- $16 to 33 M/km;
costs can vary by wall
height and bluff materials;
visual treatment can add
about 3% additional cost
Tie-back
replacement within
30 to 40 years;
average annual
costs about 5 to
10% of initial costs
Loss of tie-back
tensioning, loss of
material behind
wall; potential wall
collapse
Gravity walls
Area inland of the
wall. Due to bulk
of wall, end
erosion is likely
even if wall is
carefully tapered
into untreated
shoreline
No temporal
constraint, as
long as walls are
maintained
Effectiveness likely
to drop with
climate change;
wall height and
foundation width
may need to
increase to keep
pace with water
level.
High -- $16 to 33 M/km;
costs can vary by wall
height and foundation
stability; visual treatment, if
possible, can add about 3%
additional cost
Low -- annual
costs about 3 to
5% of initial costs
Loss of foundation
support due to
scour; wall
displacement; loss
of material behind
the wall; potential
collapse of wall
segments or total

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 145
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes
Cantilever walls
Area inland of the
wall. Possible end
erosion unless
wall is carefully
tapered into
untreated
shoreline
No temporal
constraint, as
long as walls are
maintained
Effectiveness likely
to drop with
climate change;
wall height and
foundation width
may need to
increase to keep
pace with water
level.
High -- $10 to 25 M/km; wall
height limited by foundation
depth and stability of
materials; visual treatment
can add about 3%
additional cost
Moderate to Low --
average annual
costs about 5 to
10% of initial costs
Loss of bearing
material due to
scour, loss of
material behind
the wall; potential
collapse of wall
Sand Bags
Area inland of the
sand bag
structure. Possible
end erosion
unless sand bags
are tapered into
untreated
shoreline
Bags deteriorate
fairly rapidly due
to exposure and
abrasion; bags
will need to be
repaired and
replaced
regularly
Effectiveness likely
to drop with
climate change;
bag structure
height and
foundation width
may need to
increase to keep
pace with water
level.
Low -- large bags -- 1 cy (2-
ton) sand bags about $50 to
$75/filled bag; 15 to 20
bags/ 10 linear feet for 10'
high structure
Structures need to
be rebuilt every 5
to 10 years;
maintenance cost
is about 10 to 20%
of initial cost
Individual bags
can tear, deflate,
or lose sand;
structure can
slump or lose
elevation due to
individual bag
failure or
scattering of bags
along shoreline

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 146
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes
Surge Barriers
Protects low areas
that are
hydraulically
connected to
ocean; can
exacerbate
flooding or erosion
of areas outside
surge barriers
Only when
deployed; total
replacement
likely within 50
to 75 years
Effectiveness will
drop with rising
sea level and
increased
storminess;
barriers may need
to be enlarged or
replaced to keep
pace with water
levels
Very high -- $0.67 to 3.7
M/m width.
New Orleans, Louisiana
system was about $15 B,
and about $1 B for surge
barrier elements;
St. Petersburg, Russia -
about $6 B;
Thames Barrier $2.35 B;
Venice, Italy, about $7.3 B
Moderate -- annual
costs about 5 to
10% of initial costs
Mechanical failure,
loss of power,
corrosion, marine
growth; barrier
may fail to deploy
or fail to return to
normal mode

Building Protection
Setbacks
Effective for the
building or
development
being set back
Will decrease on
an eroding coast
Effectiveness will
decrease, if
climate change
increases erosion
Low -- decrease in potential
building size due to
limitations against
development in setback None
Setback will erode
over time; risks to
development will
increase with time;
possible loss of
development to
erosion
Elevation
Effective for the
building or
development
being elevated
No temporal
constraints
Effectiveness will
decrease, if sea
level rise increases
flood levels
Low to Moderate -- $30,000
to $100,000 per residential
structure
Low -- maintain
pile support
Flooding if
elevation is not
sufficient; loss of
structure if pile
stability is lost due
to scour

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 147
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes
Sand Bags
Effective for
building or
development
being protected
No temporal
constraints
Effectiveness will
decrease, if sea
level rise increases
flood levels
Low to Moderate -- small
bags -- 1.5 cf bags (50 lbs) -
- $2 to $5 per bag or $1,000
per home, for about 3 feet
high barrier; 4.5 cu. yd bags
(5 T) ~$450 to $650 per
bag.

Low to Moderate --
for temporary
protection, removal
costs can exceed
placement costs;
replace bags every
5 to 10 years
Individual bags
can tear, deflate,
or lose sand;
structure can
slump or lose
elevation due to
individual bag
failure or
scattering of bags
along shoreline
Storm Shutters
No spatial
constraints
Only for events
with some
warning prior to
the event
No change in
effectiveness due
to climate change Low -- $30 to $50/sq ft.
Storage; need to
be replaced every
20 to 25 years
Failure to shut;
leaks, failure to
reopen

Floodproof
Vaults
No spatial
constraints
No temporal
constraints
No change due to
climate change Moderate Replace seals Leaks
Pumps
Pumping volume
needs to be
matched to
confined flood
area
During and after
events; no other
temporal
constraints
Pumping
effectiveness may
decrease with
climate change,
unless pumping
volume increases
to match potential
flood volume
Major community scale
facilities range up to $600 M
(New Orleans pump
station);
$1,000 to $5,000 per
residential size unit
Fuel Costs;
equipment
replacement every
25 to 30 years
Mechanical failure,
battery failure or
no fuel; flood
waters will rise or
remain

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 148
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes
Storm Barriers
No spatial
constraints
Only for events
with some
warning prior to
the event
Effectiveness will
decrease if sea
level rise increases
flood levels
Facility specific; cost not
available Not available
Barriers fail to
seal, leaks, and
interior flooding
Building Codes
Community-wide
program;
Property-by-
property
application
Lifetime of
development;
until substantial
improvements
Climate
change/SLR can
increase erosion,
inundation and
flooding,
decreasing
effectiveness over
time
Low -- normally 1 to 5% of
building costs
Property owner
needs to maintain
building
Building damage/
collapse

Land Use/land acquisition options

Fee simple
purchase of
land
Community-wide
program;
Property-by-
property
application
Lifetime of the
lot
Sea level rise can
increase erosion
and water levels,
decreasing
effectiveness time
period
Low to Moderate -- based
on land costs and number of
properties purchased; takes
property off tax rolls Minimal Erosion of lot

Conservation
Easements
Community-wide
program;
Property-by-
property
application
Lifetime of the
lot
Sea level rise can
increase erosion
and water levels,
decreasing
effectiveness time
period.
Low to moderate -- reduces
property values for taxes Minimal
Erosion of
easement

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 149
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes

Transfer of
Development
Credits
Community-wide
program;
Property-by-
property
application
Lifetime of the
lot
Sea level rise can
increase erosion
and water levels,
decreasing
effectiveness time
period
Low -- costs covered by
builders; no change to taxes Minimal Erosion of lot

Managed
Retreat
Community-wide
program;
Property-by-
property
application
Lifetime of the
lot
Sea level rise can
increase erosion
and water levels,
decreasing
effectiveness time
period
Low -- taxes might adjust as
building size is reduced
Periodic removal of
development Erosion of lot

Rolling
Easements
Community-wide
program;
Property-by-
property
application
Lifetime of the
lot
Sea level rise can
increase erosion
and water levels,
decreasing
effectiveness time
period
Low -- taxes might adjust as
building size is reduced
Periodic removal of
development Erosion of lot

Table A-2. Coastal Protection Options – Effectiveness, Costs and Failure Modes
Page 150
Technique
Details/
Structure
Details
Spatial
Effectiveness
Temporal
Effectiveness
Effectiveness
with Climate
Change
Initial Project Costs
Very high; > $10 US M/km
or $1B US per project;
High: $5 - 10 US M/km;
Moderate: $1 – 5 US
M/km; Low: < $1 USM/km
Maintenance
Requirements
Failure Modes
Miscellaneous
Insurance
No spatial
constraints
No temporal
limits
No constraints;
premiums may
increase
Low to moderate -- costs
depend upon hazard
exposure
Continued
payments
Useful, only if
there is building
damage; if claims
far exceed
available funds,
program could
declare
bankruptcy.

Early Warning
Systems
No spatial
constraints
Only for events
with possible
warning prior to
the event
No change due to
rising sea level
Very high to moderate --
costs to set-up initial system
are very high; costs to
individual communities once
system is available is
moderate
5 to 10% of initial
costs
Buoys or satellites
fail to record
events; warning
not conveyed or
not conveyed in a
timely manner,
warning does not
trigger evacuation.
Or, overly
conservative
warnings cause
future warnings
not to be taken
seriously

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 151

Table A-3. Coastal Protection Options – Disaster Protection Values
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value
Beach Enhancement (Individual projects or part of a Regional Sediment Management Program; enhancement methods discussed in previous tables)

Beach
Enhancement
Soft Resistance
through
maintenance of
beach width;
protection will
depend upon
volume of beach
sand and width of
dry beach
Protect from early
storm conditions
A wide beach can reduce
erosion and wave impacts;
protection likely to
decrease during event due
to erosion; beach width
alone cannot reduce
flooding
Beach widths between
100 to 300 feet can
protect inland
development from small
and moderate storm and
erosion events
subsequent to disaster
Persistent beach widths
between 100 to 300 feet
can protect inland
development from small
and moderate storm and
erosion events

Retain Sand Material

Sand
Backpassing
Soft Resistance
through
maintenance of
beach width;
protection will
depend upon
volume of beach
sand and width of
dry beach
Protect from early
storm conditions
A wide beach can reduce
erosion and wave impacts;
protection likely to
decrease during event due
to erosion; beach width
alone cannot reduce
flooding
Restored beach widths
between 100 to 300 feet
can protect inland
development and
recovery efforts from
small and moderate
storm and erosion
events subsequent to
disaster
Persistent beach widths
between 100 to 300 feet
can protect inland
development from small
and moderate storm and
erosion events

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 152
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value
Beach berms
Soft Resistance
through
maintenance of back
beach elevation
Protect from early
storm conditions
A wide beach and high
berm can reduce erosion
and wave impacts;
protection likely to
decrease during event due
to erosion; berm can
reduce flooding more than
beach alone
Restoring berms can
protect inland
development and
recovery efforts from
small and moderate
storm and erosion
events subsequent to
disaster
Persistent beach widths
between 100 to 300 feet
with elevated back shore
berms can protect inland
development from small
and moderate storm and
erosion events
Groins
Soft Resistance
though maintenance
of beach width;
protection will
depend upon
volume of beach
sand and width of
dry beach
Protect from early
storm conditions
A wide beach can reduce
erosion and wave impacts;
protection likely to
decrease during event due
to erosion; beach width
alone cannot reduce
flooding
Segments of beach
between groins can be
selectively renourished
for targeted protection of
key recovery areas
Persistent beach widths
between 100 to 300 feet
can protect inland
development from small
and moderate storm, and
from erosion events
Jetties
Soft Resistance
though maintenance
of beach width;
protection will
depend upon
volume of beach
sand and width of
dry beach
Protect navigation
channel; allow boats
to safely leave harbor
for deep water
A wide beach can reduce
erosion and wave impacts;
protection likely to
decrease during event due
to erosion; beach width
alone cannot reduce
flooding
If sediment has not
made channels unsafe,
ships can use navigation
channel to bring in
goods and supplies for
search and rescue, and
recovery
Persistent beach widths
between 100 to 300 feet
can protect inland
development from small
and moderate storm, and
erosion events

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 153
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value
Perched beach
Soft Resistance
through
maintenance of
beach width;
protection will
depend upon
volume of beach
sand and width of
dry beach
Protect from early
storm conditions
Perched beach can reduce
erosion and wave impacts;
sill can reduce wave
impacts; protection likely to
decrease during event due
to erosion
Beach restoration not
likely to occur without
nourishment; isolated
beach segments with
sills can be selectively
renourished for targeted
protection of key
recovery areas
Persistent beach width
with sill can protect inland
development from small to
moderate storm and
erosion events

Breakwaters-
submerged
Reduce onshore
wave energy and
wave impacts by
causing waves to
break on structure
Calm water area
inland of breakwater;
protect from early
storm conditions
Reduce storm waves and
onshore wave energy;
inland beach can also
reduce wave impacts,
erosion and flooding;
protection will decrease,
but not as slowly as
unprotected beach
Calm water inland of
breakwater can hasten
beach recovery; restored
beach widths and
reduced wave energy
can protect inland
development and
recovery efforts from
small and moderate
storm and erosion
Persistent beach width and
reduced wave energy can
protect inland development
from small and moderate
storm and erosion events

Breakwaters -
emergent
Reduce onshore
wave energy and
wave impacts by
causing waves to
break on structure
Calm water area
inland of breakwater;
protect from early
storm conditions
Reduce storm waves and
onshore wave energy;
inland beach can also
reduce wave impacts,
erosion and flooding;
protection will decrease,
but not as slowly as
unprotected beach
Calm water inland of
breakwater can hasten
beach recovery; restored
beach widths and
reduced wave energy
can protect inland
development and
recovery efforts from
small and moderate
storm and erosion
Persistent beach width and
reduced wave energy can
protect inland development
from small and moderate
storm and erosion events

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 154
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value

Breakwaters -
floating
Block wave impacts
at isolated offshore
region; small inland
benefits
Little benefit; not likely
to be used prior to
disaster
Little benefit; anchors likely
to be dislodged during high
wave events
Provide safe anchorage,
and enable ships to
bring in goods and
supplies for search and
rescue and recovery
Little benefit; floating
breakwaters normally
temporary structures

Delta
augmentation
Reduce onshore
wave energy and
wave impacts by
causing waves to
break on structure
Calm water area
inland of breakwater;
protect from early
storm conditions
Reduce storm waves and
onshore wave energy;
inland beach can also
reduce wave impacts,
erosion and flooding;
protection will decrease,
but not as slowly as
unprotected beach
Calm water inland of
delta can hasten beach
recovery; restored beach
widths and reduced
wave energy can protect
inland development and
recovery efforts from
small and moderate
storm and erosion
Persistent beach width and
reduced wave energy can
protect inland development
from small and moderate
storm and erosion events

Artificial
headland
Soft Resistance
though maintenance
of beach width;
protection will
depend upon
volume of beach
sand and width of
dry beach
Protect from early
storm conditions
A wide beach can reduce
erosion and wave impacts;
protection likely to
decrease during event due
to erosion; beach width
alone cannot reduce
flooding
Segments of beach
between upcoast of
headlands can be
selectively renourished
for targeted protection of
key recovery areas
Persistent beach widths
between 100 to 300 feet
can protect inland
development from small
and moderate storm and
erosion events

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 155
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value

Beach
dewatering -
active or
passive
Soft Resistance
through
maintenance of
beach width;
protection will
depend upon
volume of beach
sand and width of
dry beach
Protect from early
storm conditions
A wide beach can reduce
erosion and wave impacts;
protection likely to
decrease during event due
to erosion; beach width
alone cannot reduce
flooding
Restored beach widths
between 100 to 300 feet
can protect inland
development and
recovery efforts from
small and moderate
storm and erosion
Persistent beach widths
between 100 to 300 feet
can protect inland
development from small
and moderate storm and
erosion events

Habitat protection

Wetland,
marsh or
mangrove
protection and
enhancement
Reduce wave height
and wave energy
Protect from early
storm conditions
A broad, stabilized
wetland, marsh or
mangrove can cause a
significant reduction in
wave height, wave energy
and surge. Assumed
benefits for New Orleans
were 1 to 2 meter surge
reduction and 0.6 meter
reduction in wave height
Protection provided by
wetlands, marshes and
mangroves may diminish
after a major storm event
and might need several
growing seasons to
return to full protection
Protection from small and
medium storm events

Dune
enhancement
Soft Resistance
through
maintenance of back
beach elevation and
roughness from
vegetation; solid
core can reduce
wave energy even
with sand erosion
Protect from early
storm conditions
A beach and high, broad
dune can reduce erosion
and wave impacts;
protection likely to
decrease during event due
to erosion; protection from
solid core will not decrease
during event
Restoring dunes can
protect inland
development and
recovery efforts from
small and moderate
storm and erosion
events subsequent to
disaster
Persistent beach and
elevated back shore dunes
can protect inland
development from small
and moderate storm and
erosion events

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 156
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value

Multi-purpose
Reef
Reduce onshore
wave energy and
wave impacts by
causing waves to
break on structure
Calm water area
inland of breakwater;
protect from early
storm conditions
Reduces storm waves and
onshore wave energy;
inland beach can also
reduce wave impacts,
erosion and flooding;
protection will decrease,
but not as slowly as
unprotected beach
Calm water inland of
breakwater can hasten
beach recovery; restored
beach widths and
reduced wave energy
can protect inland
development and
recovery efforts from
small and moderate
storm and erosion
Persistent beach width and
reduced wave energy can
protect inland development
from small and moderate
storm and erosion events
Habitat buffers
Provides space for
habitat expansion NA
Alleviates flooding by
providing overflow area
Buffer area can reduce
post-event disturbance
and promote new growth
Buffer area can help
promote on-going habitat
growth and stability

Living
shorelines
Reduce wave height
and wave energy
Protect from early
storm conditions
Reduces wave height,
wave energy and surge;
diminishes protection
during the disaster; sill will
provide more protection,
for width, than wetlands,
marshes and mangroves
Living shorelines likely to
need to be rebuilt after a
large event; some
regrowth will occur
naturally, if sill remains
and can provide erosion
control and a stable
substrate
Protection from small and
medium storm events

Engineered Protection
Levees
Protection from
wave energy and
flooding
Opportunity to secure
site and for safe
evacuation if needed
Blocks wave energy and
prevents flooding;
overtopping a stable levee
can cause some flooding;
breach can result in
flooding to full surge depth
Surviving structures
protect recovery efforts
and help hasten
community recovery
Protection from small and
medium events

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 157
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value

Horizontal
Levees
Protection from
wave energy and
flooding
Opportunity to secure
site and for safe
evacuation if needed
Blocks wave energy and
prevents flooding;
overtopping a stable levee
can cause some flooding;
breach can result in
flooding to full surge depth
Surviving structures
protect recovery efforts
and help hasten
community recovery
Protection from small and
medium events
Revetments
Protection from
wave energy and
flooding
Protection from early
storm conditions
Blocks wave energy and
prevents erosion;
overtopping a stable
revetment can cause some
flooding; breach can result
in erosion and flooding to
full surge depth
Surviving structures
protect recovery efforts
and help hasten
community recovery
Protection from small and
medium events

Dynamic
Revetment
Protection from
wave energy and
flooding
Protection from early
storm conditions
Blocks wave energy and
prevents erosion;
overtopping a stable
revetment can cause some
flooding; breach can result
in erosion and flooding to
full surge depth
Surviving structures
protect recovery efforts
and help hasten
community recovery
Protection from small and
medium storm events

Seawalls (tied-
back, gravity or
cantilever)
Protection from
erosion and flooding
Protection from early
storm conditions
Blocks wave energy and
prevents erosion;
overtopping a seawall can
cause erosion and
possible structural collapse
Surviving structures
protect recovery efforts
and help hasten
community recovery
Protection from small and
medium storm events
Sand Bags
Protection from
erosion and flooding
Deployed before the
event
Reduces flooding; can add
1 to 3 meters of additional
height on levees and
revetments
Temporary protection for
recovery efforts and help
community recovery
Temporary protection from
small and medium storm
events

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 158
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value
Surge Barriers
Protection from
wave energy and
flooding
Opportunity to secure
site and for safe
evacuation if needed
Barrier to waves, currents
and flooding; overtopping
can cause flooding and
overtax pumps
Surviving structures can
protect recovery efforts
and help hasten
community recovery
Protection from major
events; can respond to
multiple events without
need for recovery
Building Protection
Setbacks
Protection from
erosion
Protects from early
storm conditions
Allows some erosion
without damage to
development
Setbacks, like open
space, can be used for
recovery efforts
On-going accommodation
of erosion
Elevation
Protection from
flooding
Protects from early
storm conditions
Protects from flooding up
to elevation of
development; reduce
damage even if flooded None None
Sand Bags
Protection from
scour and flooding
Must be deployed
prior to event
Reduces flood up to the
elevation of the bags;
reduce scour of
foundations
None; may need to be
part of recovery since
sand bags will need to
be removed None
Storm Shutters
Protection from
flooding
Must be deployed
prior to event
Prevents water from
entering into buildings
Protection for future
events
Protection for small and
moderate events

Floodproof
Vaults
Protection from
flooding
Protects from early
storm conditions
Prevents water exposure
to items within the vault
Protection for future
events Protection for future events
Pumps
Protection from
flooding damage
Protects from early
storm conditions
Removes water from
flooded areas, basements,
or the inland side of surge
barriers
Protection for future
events Protection for future events
Storm Barriers
Protection from
flooding
Must be deployed
prior to event
Prevents water from
entering into tunnels, and
other subterranean areas
Protection for future
events Protection for future events

Table A-3. Coastal Protection Options – Disaster Protection Values
Page 159
Technique
Details/
Structure
Details
Coastal Hazard
Protection
Disaster Protection
Pre-Event Value
Disaster Protection
Event Value
Disaster Protection
Recovery Value
Disaster Protection On-
going Value
Building Codes
Specifications for
foundations that
resist scour and
resist or dampen
wave energy;
structures that
accommodate
flooding N/A
Avoids or minimizes
damage to building and
loss of property
Surviving building stock
can greatly increase
recovery efforts by
providing a foundation
for community rebuilding
On-going protection for
small and moderate storm
events
Land Use/land acquisition options

Land
acquisitions,
Easements,
and Retreat
Options
Accommodate
erosion;
Buffer/reduce wave
energy;
Buffer/reduce
flooding N/A
Open space and
easements can alleviate
flooding by providing
overflow area
Easements and open
space can be used for
recovery efforts
On-going accommodation
of erosion; can help
promote on-going habitat
growth and stability

Miscellaneous
Insurance N/A N/A N/A
Funding for recovery
efforts N/A

Early Warning
Systems N/A
Saves lives by
providing opportunity
for evacuation;
provide time to protect
equipment that can be
shut down or put on
safety model and to
activate surge barriers Similar to pre-event value
Peace of mind for
recovery efforts, knowing
there will be some
warning time N/A

Table A-4. Coastal Protection Options – Values During Recovery
Page 160

Table A-4. Coastal Protection Options – Values During Recovery
Technique Details/
Structure Details
Economic Value to
Community During
Recovery
Rec’ry
Econ.
Value (#)
Environmental Value
to Community During
Recovery
Rec’vy
Env.
Value (#)
Social/ Cultural Value to
Community During
Recovery
Rec’vy
Social Cult.
Value (#)
Beach Enhancement (Individual projects or part of a Regional Sediment Management Program; enhancement methods described in previous
tables)
Beach Enhancement Null to Moderate 0 to 2 Moderate 2 High 3

Retain Sand Material
Sand Backpassing
Low -- may encourage
more rapid recovery 1
Negative, Low -- Sand
movement can disturb
habitat & air quality -1 Moderate 2
Beach berms
Low -- may encourage
more rapid recovery 1
Negative, Low -- Sand
movement can disturb
habitat & air quality -1 Moderate 2
Groins
Low - may encourage
more rapid recovery 1
Negative, Low --
Structures are likely
locations for debris -1 Null 0
Jetties
High -- may support
shipping and delivery
of recovery supplies 3 Null 0 Null 0
Perched beach
Null -- sand likely to
be removed so no
value till restored 0
Negative, Null to Low --
stagnant water can
collect inland of sill -1
Negative, Null to Low --
reduces coastal access
areas until beach is
restored -1

Breakwaters-
submerged and
emergent
High -- may provide
safe area for
anchorage or
improved navigation 3
Moderate -- provides
habitat 2 Moderate 2

Table A-4. Coastal Protection Options – Values During Recovery
Page 161
Technique Details/
Structure Details
Economic Value to
Community During
Recovery
Rec’ry
Econ.
Value (#)
Environmental Value
to Community During
Recovery
Rec’vy
Env.
Value (#)
Social/ Cultural Value to
Community During
Recovery
Rec’vy
Social Cult.
Value (#)
Breakwaters - floating
High -- may provide
safe area for
anchorage or
improved navigation 3
Negative, Low to
Moderate -- disturbs
nearshore area for
anchoring, possible
water quality problems -1 to -2 Null 0
Delta augmentation
Low -- may encourage
more rapid recovery 1 Null 0 Null 0
Artificial headland
Low -- may encourage
more rapid recovery 1 Null 0 Null 0

Beach dewatering -
active or passive
Null -- sand likely to
be removed so no
value till restored 0
Negative, Null to Low --
dewatering system may
become beach debris 0 to -1 Null 0

Habitat protection

Wetland, marsh or
mangrove protection
and enhancement
Low -- based on
summary study of
ecosystem function 1
High -- based on
summary study of
ecosystem function 3
Low -- based on
summary study of
ecosystem function 1
Dune enhancement Null to Moderate 0 - 2 Moderate 2 High 3
Multi-purpose Reef
Low based on
summary study of
ecosystem function 1
High -- based on
summary study of
ecosystem function
Moderate -- based on
summary study of
ecosystem function
Habitat buffers
Negative -- Low to
moderate; less land
on tax rolls to support
new services -2 Moderate 2 Moderate 2
Living shorelines
Low -- comparable to
wetlands 1
Moderate -- less value
than wetlands 2
Low -- comparable to
wetlands 2

Table A-4. Coastal Protection Options – Values During Recovery
Page 162
Technique Details/
Structure Details
Economic Value to
Community During
Recovery
Rec’ry
Econ.
Value (#)
Environmental Value
to Community During
Recovery
Rec’vy
Env.
Value (#)
Social/ Cultural Value to
Community During
Recovery
Rec’vy
Social Cult.
Value (#)
Engineered Protection
Levees
Low -- may encourage
more rapid recovery 1 Null 0 Null 0
Horizontal Levees
Low -- may encourage
more rapid recovery 1 Low 1 Null 0
Revetments
Low -- may encourage
more rapid recovery 1
Negative, Null to Low --
may trap debris 0 to -1 Null 0
Dynamic Revetment
Low -- may encourage
more rapid recovery 1 Low 1 Null 0

Seawalls (tied-back,
gravity or cantilever)
Low -- may encourage
more rapid recovery 1 Null 0 Null 0
Sand Bags
Negative, Low -- must
be removed -1
Negative, Low -- may
add to beach debris -1 Null 0
Surge Barriers
Low -- may
encourage more rapid
recovery 1 Null 0 Null 0
Building and Asset Protection

Building Protection &
Building Codes
Moderate to high --
more properties may
return to service and
support tax base 3
Low -- potentially less
debris and need for
clean-up due to better
building design and pre-
disaster protection 1 Null 0

Table A-4. Coastal Protection Options – Values During Recovery
Page 163
Technique Details/
Structure Details
Economic Value to
Community During
Recovery
Rec’ry
Econ.
Value (#)
Environmental Value
to Community During
Recovery
Rec’vy
Env.
Value (#)
Social/ Cultural Value to
Community During
Recovery
Rec’vy
Social Cult.
Value (#)
Land Use/land acquisition options

Land acquisitions,
easements, and retreat
options
Negative, Low -- to
moderate; less
properties on tax rolls
to support new
services -2 Moderate to High 2 to 3 Moderate to High 2 to 3
Miscellaneous
Insurance
High -- fund new
building to support tax
base 3
Negative, Low -- Can
support rapid rebuilding
that can put a strain on
environmental resources -1
Negative, Low -- Reduce
access during
construction -1
Early Warning Systems
Moderate to high --
more services may be
available due to pre-
disaster preparation 2 to 3
Low -- less debris and
need for clean-up due to
pre-disaster preparation 1
Moderate -- more people
might participate in
recovery 2

Table A-5. Coastal Protection Options – Values During On-going Activities
Page 164

Table A-5. Coastal Protection Options – Values During On-going Activities
Technique Details/
Structure Details
On-going Economic
Value to Community
On-going
Econ. Value
(#)
On-going
Environmental Value
to Community
On-going
Env.
Value (#)
On-going Social/
Cultural Value to
Community
On-going
Social Cult.
Value (#)
Beach Enhancement (Individual projects or part of a Regional Sediment Management Program)

Beach Enhancement --
enhancement methods
covered in previous
tables
High -- important
tourist attraction 3 Moderate 2 High 3

Retain Sand Material
Sand Backpassing
Null -- backpassing
costs probably
balance benefits 0
Negative, Low -- Sand
movement can disturb
habitat & air quality -1 Moderate 2
Beach berms Low 1
Negative, Low -- Sand
movement can disturb
habitat & air quality -1 Moderate 2
Groins Null 1
Negative, Low --
Structures are likely
locations for debris and
vermin -1 Null 0
Jetties
High -- may support
shipping and
navigation 3
Negative, Low --
Structures are likely
locations for debris and
vermin -1 Null 0
Perched beach
Null -- sand likely to
be removed so no
value till restored 0
Low -- provides some
intertidal habitat 1 Moderate 2

Breakwaters-
submerged and
emergent
High -- may provide
safe area for
anchorage or
improved navigation 3
Moderate -- provides
submerged habitat 2 Moderate 2

Table A-5. Coastal Protection Options – Values During On-going Activities
Page 165
Technique Details/
Structure Details
On-going Economic
Value to Community
On-going
Econ. Value
(#)
On-going
Environmental Value
to Community
On-going
Env.
Value (#)
On-going Social/
Cultural Value to
Community
On-going
Social Cult.
Value (#)
Breakwaters - floating Low 1
Negative, Low to
Moderate -- disturbs
nearshore area for
anchoring, possible
water quality problems -1 to -2 Null 0
Delta augmentation
Low -- some tourist
value 1
Low -- provides some
submerged habitat 1 Null 0
Artificial headland
Low -- some tourist
value 1
Low -- provides some
intertidal habitat 1 Null 0

Beach dewatering -
active or passive
Low -- some tourist
value 1 Null 0 Null 0
Habitat protection

Wetland, marsh or
mangrove protection
and enhancement
Low -- based on
summary study of
ecosystem function 1
High -- based on
summary study of
ecosystem function 3
Low -- based on
summary study of
ecosystem function 1
Dune enhancement Moderate 2 High 3 High 3
Multi-purpose Reef
Low -- based on
summary study of
ecosystem function 1
High -- based on
summary study of
ecosystem function
Moderate -- based on
summary study of
ecosystem function
Habitat buffers
Negative, Low to
moderate -- less land
on tax rolls to support
new services -2 Moderate 2 Moderate 2
Living shorelines
Low -- comparable to
wetlands 1
Moderate -- less value
than wetlands 2
Low -- comparable to
wetlands 2
Engineered Protection
Levees Null 0
Negative, low to
moderate -- blocks
natural ecosystem -1 to -2 Null 0

Table A-5. Coastal Protection Options – Values During On-going Activities
Page 166
Technique Details/
Structure Details
On-going Economic
Value to Community
On-going
Econ. Value
(#)
On-going
Environmental Value
to Community
On-going
Env.
Value (#)
On-going Social/
Cultural Value to
Community
On-going
Social Cult.
Value (#)
Horizontal Levees Null 0 Low to moderate 1 to 2 Null 0
Revetments Null 0
Negative, low to
moderate -- encroaches
on beach ecosystem -1 to -2
Negative, moderate to
high -- reduces access
and beach experience -2 to -3
Dynamic Revetment Null 0
Negative, low --
encroaches on beach
ecosystem -1
Negative, low to
moderate -- reduces
access and beach
experience -1 to -2

Seawalls (tied-back,
gravity or cantilever) Null 0
Negative, low --
encroaches on beach
ecosystem -1
Negative, low to
moderate -- reduces
access and beach
experience -1 to -2
Sand Bags Null 0
Negative, Low to
moderate -- if left on
beach -1 to -2
Negative, moderate to
high -- reduces access
and beach quality -2 to -3
Surge Barriers 0 Null 0 Null 0
Building and Asset Protection

Building Protection &
Building Codes
Low -- may increase
property values and
taxes 1 Null 0 Null 0

Land Use/land acquisition options

Land acquisitions,
easements, and retreat
options
Negative, Low to
moderate -- less
properties on tax rolls
to support new
services -2 Moderate to High 2 to 3 Moderate to High 2 to 3

Table A-5. Coastal Protection Options – Values During On-going Activities
Page 167
Technique Details/
Structure Details
On-going Economic
Value to Community
On-going
Econ. Value
(#)
On-going
Environmental Value
to Community
On-going
Env.
Value (#)
On-going Social/
Cultural Value to
Community
On-going
Social Cult.
Value (#)
Miscellaneous
Insurance
Negative, Low --
expense for
community -1 Null 0 Null 0
Early Warning Systems Null 0 Null 0 Null 0

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Abstract (if available)

Abstract Coastal communities are some of the major economic centers in both the US and the world

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Creator Ewing, Lesley Carol (author)

Core Title Community resilience to coastal disasters

School Viterbi School of Engineering

Degree Doctor of Philosophy

Degree Program Civil Engineering (Environmental Engineering)

Publication Date 08/06/2014

Defense Date 03/14/2014

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag coastal disasters,hazards,OAI-PMH Harvest,resilience,sea level rise,Shore protection,Storms,tsunamis,vulnerability

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Language English

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Advisor Synolakis, Costas (committee chair), Flick, Reinhard (committee member), Lynett, Patrick J. (committee member), Mazmanian, Daniel A. (committee member)

Creator Email lewing@coastal.ca.gov

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c3-454096

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Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA