University of Southern California Dissertations and Theses

Synoptic Surf Zone Sedimentation Patterns

(USC Thesis Other)

Synoptic Surf Zone Sedimentation Patterns

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content SYNOPTIC SURF ZONE SEDIMENTATION PATTERNS by Benno Max Brenninkmeyer, S.J. A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (Geological Sciences) June 1973 INFORMATION TO USERS This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication th at the photographer suspected th at the copy may have moved during exposure and thus cause a blurred image. You will find a good image of the page in the adjacent frame. 3. When a map, drawing or chart, etc., was part of the material being photographed the photographer • followed a definite method in "sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large sheet and to continue photoing from left to right in equal sections with a small overlap. If necessary, sectioning is continued again — beginning below die first row and continuing on until complete. 4. The majority of users indicate that the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding of the dissertation. Silver prints of "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced. 5. PLEASE NOTE: Some pages may have indistinct print. Filmed as received. Xerox University Microfilms 300 North Zeeb Road Ann Arbor, Michigan 48103 H l 73-31,633 ERENNJNKMEYER, S. J., Benno Max, 1940- SYNOPTIC SURF ZONE SEDIMENTATION PATTERNS. University of Southern California, Ph.D., 1973 Geology University Microfilms, A X ERO X Company, Ann Arbor, Michigan Q ) Copyright by Benno Max Brenninkmeyer, S.J. 1973 THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED. U N IV ER SITY O F S O U T H E R N C A L IFO R N IA THE GRADUATE SCHOO L UNIVERSITY PARK LO S ANGELES, CA LIFO R N IA 8 0 0 0 7 This dissertation, written by Benno Max Brenninkmeyer under the direction of h.ds... Dissertation Com mittee, and approved by all its members, has been presented to and accepted by The Graduate School, in partial fulfillment of requirements of the degree of D O C T O R OF P H I L O S O P H Y D ate... DISSERTATION COMMITTEE Chairman CONTENTS Page ABSTRACT ................................... INTRODUCTION ............................... 1 General statement ........................ 1 Terminology .............................. 2 Measurement units ........................ 6 Sediment movement ........................ 7 List of symbols.......................... 8 Data storage............................ 11 Acknowledgments .......................... 11 SEDIMENT MOVEMENT............................ 13 State of the a r t ..................... . 13 Suspended sediment ...................... 16 Sand movement normal to the Coast......... 18 Depth of water for sediment movement ... 23 Depth of sand movement.................. 24 Suspended sediment ...................... 24 THE ALMOMETER............................... 29 General statement ........................ 29 The almometer........................... 29 Calibration............................. 39 11 Page POINT MUGU, CALIFORNIA ..................... 54 General statement ....................... 54 Description of the area................. 57 Atmospheric and sea conditions ...... 60 Winds............................... 60 Tides............................... 64 Sea state........................... 64 Waves and swell..................... 65 Littoral processes ..................... 73 Sediment distribution ................... 75 Profile development ..................... 87 ALMOMETER MEASUREMENTS OF SEDIMENT MOVEMENT . . 92 General statement ....................... 92 Computer techniques ..................... 95 Limitations............................. 97 Tidal cycle sand movement.................... 108 Demise of a b e r m ............................ 119 SAND FOUNTAINS................................. 128 General statement ............................ 128 Extent and location of sand fountains . . . 128 Shape of the suspension clouds.............. 145 Quantity of sand moved by suspension . . . 152 Causes of sand suspension In the surf zone 156 ill Page SAND MOVEMENT ACROSS THE SURE ZONE........... 164 Spectral analysis ...................... 177 CONCLUSIONS............................... 208 REFERENCES................................. 215 APPENDICES................................. 255 Appendix I ............................. 236 Appendix I I ............................ 247 Appendix III ...................... 258 Appendix I V ............................ 267 Appendix V .............................. 269 Appendix V I ............................ 273 iv ILLUSTRATIONS Figure Page 1. Coastal geomorphologlcal terminology and principal dynamic zones .............. 4 2. The almometer and its electrical com ponents .............................. 30 3. Disposition of the almometers in the surf zone at Point M u g u .............. 34 4. Rotating the steel pipes out of the sand for the lower "beach face almometer; the almometer and a wave height measurement device on top of the berm crest .... 37 5. The Pacific Missile Range Special Measurements Van and living quarters . . 41 6. Setup for the calibration of the photo electric cells.................. 46 7. Calibration curve of photoelectric cell C1905HL....................... 48 8. Vicinity map of Arnold Road Beach at Point Mugu, California ................ 55 9. U. S. Army Corps of Engineers conducting RIST test at Point Mugu, California . . 58 10. Annual and monthly wind rose at Point Mugu........................... 61 11. Sea state at Point Mugu September 29 to October 8, 1 9 7 1 ................ 66 12. Diagrammatic illustration of waves ap proaching Point Mugu............ 68 13. Swell and sea height and period in the Santa Barbara Basin............ 71 v Figure Page 14. Mean sediment size in the middle swash zone on the beach and shore face at Arnold Road Beach, Point Mugu, Cali fornia ................................ 77 15* Mean sediment size in the middle swash zone on the beach and shore face at Arnold Road Beach, Point Mugu, separated into differences by tidal phase ........................ 80 16. Tidal curves at Rincon Point, California and fluctuations in the skewness of the sediment distribution of the middle swash zone at Arnold Road Beach with the tide from September 28 to October 8, 1971 . . 84 17. Profiles of the beach at Point Mugu from the U. S. Army Corps of Engineers base line to the breaker zone.............. 88 18. Measurements of sediment concentration changes with increasing height above the bottom on the upper beach face......... 93 19. Bata for three almometer smoothed by computer for September 30, 1972 from 9200-0800 98 20. Data from three almometers smoothed by computer for September 30, 1972 from 1900 hours to October 1, 1972 at 0100 hours..................................... 100 21. Data from three almometers smoothed by computer for October 1, 1972 from 0200 to 0800 hours............................. 102 22. Localized scour around the almometer cylinder................................... 105 23. Smoothed record of the maximum short term changes in bottom elevation in the surf z o n e ................................. 116 vi Figure Page 24. Changes in the summer berm elevation with the advent of spring tides October 3 to 8, 1 9 7 1 ................................ 122 25. Sand fountain on upper beachface Sep tember 30 22:40 Ebb Tide 2.7 f t ........ 129 26. Sand fountain on upper beachface Sep tember 30 22:53 Ebb Tide 2.1 f t ........ 131 27. Sand fountain on shore face October 2, 1433, flood tide 0.7 f t ................ 133 28. Height versus duration of sand fountains on the shoreface and lower beachface and upper beachface with changes in tidal elevation.............................. 141 29. Frequency of occurrence of sand fountains on the upper beachface.................. 143 30. Frequency of occurrence of sand fountains on the upper beachface.................. 147 31. Quantity of sand transported in suspension per strip 1 foot wide per tide.......... 154 32. Changes in horizontal water velocity across the inshore and foreshore ........ 159 33. Two minute record of elevation changes across the foreshore (I), lower beach face (II), and upper beach face (III) of the 135 gm/l concentration during the seaward traverse of a backwash.................. 165 34. Two minute record of elevation changes across the foreshore (I), lower beach face (II) and upper beach face (III) of the 135 gm/l concentration Bhowing an Increase in suspension as a backwash moves seaward I67 vil Figure 35. Two minute record of elevation changes across the lower beach face (II) and upper beach face (III) of the 135 gm/l concentration showing sediment sus pension and redistribution in an in coming b o r e ........................... 36. Two minute record of elevation changes across the foreshore (I), the lower beach face (II), and upper beach face (III) of the 135 gm/l concentration under an in coming bore ..... ................. 37* Sand fluctuations throughout the beach . . 38. Two minute record of elevation changes across the foreshore (I), lower beach face (II) and upper beach face (III) of three sediment concentrations 375 gm/l (l)> 75 gm/l (2), and 40 gm/l at high tide................................... 39. Two minute record of elevation changes across the foreshore (I), lower beach face (II), and upper beach face (III) of three sediment concentrations 375 gm/l (1), 75 gm/l (2), and 40 gm/l at low tide................................... 40. Power spectrum of the 70 gm/l sand con centration In the inner surf zone . . . . 41. Power spectrum of the 40 gm/l sand con centration in the offshore zone 42. Power Bpectrum of the 375 gm/l sand con centration In the outer surf zone . . . . 43. Power spectrum of the 40 gm/l concentra tion In the inner surf zone 44. Power spectrum of the 375 gm/l sand con centration in the inner surf zone . . . . 45. Wave and 40 and 375 gm/l spectra for the outer and Inner surf and swash zones . . . Page 170 172 176 179 182 188 191 193 195 197 200 viii Figure Page 46. Wave and 40 and 375 gm/l spectra for the breaker, middle surf and still water level zones............................ 202 47. Wave and 40 and 375 gm/l spectra for the offshore and outer and inner surf zones . 204 ix Table Page 1. Response time versus light Intensity of photoelectric cell CL905HL............. 36 2. Fluctuations In the amount of sand and water inspired during the calibration of the photoelectric cells ................. 51 3. Monthly averages and extremes of surface winds at Point Mugu..................... 63 4. Summary of the maximum erosion and deposition and the time of their occurrence in relation to high tide across the surf z o n e ...................................... 109 5. Summary of topographic changes in the destruction of a summer berm by spring tides...................................... 125 6. Distribution of sand fountains across the surf zone with changes in tidal elevation . 135 7. Classification and occurrence of sand fountain types ............................ 149 x INTRODUCTION General Statement A major endeavor in marine geology is the study of erosion, transportation and deposition of sediment on the sea floor. Nowhere in the marine environment do these pro cesses operate more efficaciously than in the nearshore zone. All the detritus eroded from the continent must pass through this belt of wave action. Models of sedi ment transport in this zone supported by extensive labora tory tests In wave tanks and Lagranglan field methods and solutions based on wave mechanics have been constructed. Yet, in many examples, the observations made under natural conditions show little correlation either with the model studies or with theoretical solutions based on fluid dynamic considerations. Problems inherent in scaling sedi ment parameters and hydrodynamic attributes impose limita tions to wave tank experiments (Powell, 1955)* The fluid dynamic solutions approach reality only if the secondary effects are taken into account (Wells, 1967). Even the field measurements, since many of them are baBed on track ing tracers, are limited by problems of depletion and variable dispersion due to apparent mass transport effects 1 (Price, 1969)- This study was undertaken to determine "by Eularian means the behavior of shoreface and beachface sediments under the influence of breaker, surf and swash regimes. A new device, the almometer, measures instantaneously the changes in topography, the thickness of the bedload and changes in concentration with depth of suspended load as sociated with individual waves. The primary objective of this study was the determination of factors affecting synoptic surf zone sedimentation patterns. Terminology The nomenclature of beach geomorphology used throughout this report is culled primarily from Wiegel (1953), King (1959, p. 48-50), Beach Erosion Board (1933), Coastal Engineering Research Center (1966), Shepard (1963, p. 168-170) and Ingle (1966, p. 11-13). However, diverse usage among coastal workers requires standardization of terms. Therefore the basic terms will be defined here. The backshore is the area of the beach above the limits of the ordinary swash and is only acted upon by waveB during severe storms (= back beach; Wiegel, 1953)* The foreshore is that part of the beach lying between the seaward berm and the mean lower low water mark (= beach face; Ingle, 1966). It Is the area traversed by the up- rush and backwash as the tide rises and falls. The Inshore 3 ie the beach area lying between mean lower low water and that area alwaye covered by water (= shoreface). The off shore zone extends from the uppermost point always covered by water to a depth where "substantial" movement of sand ceases (King, 1959). The nearshore is the indefinite zone extending seaward from the shoreline to where the waves transform from primarily sinusoidal or trochoidal form to a basically solitary form at some distance from the breaker zone (OERC, 1966; Cook, 1970). The main topographic features of the coastal environment are shown in Figure 1. The terms bar, either by itself or preceded by sub marine . longshore or offshore and ball, full, ridge beside, riff, bank, nehrung. schwellen. aangroellngrug as well as slllon prelltteraux and barre. and their opposites trough. rifftalen. mulden. zwlnn and crete prelltteraux have had a long and complicated history (e.g., Hagen, 1863; Lehman, 1884; Gilbert, 1885» 1890; Cornish, 1889; de Martonne, 1926; Timmermans, 1935; Evans, 1942; Shepard, 1942; and Guilcher, 1954). Part of the difficulty stems from dif ferences in environments examined by the various investi gators; some worked in lakes, others on the seashore. In order to obviate these diverse usages the term bar will be used to denote a positive topographic feature never ex posed above the water level while ridges are those which are, for part of the time at least, above the still water level. Figure 1 Coastal geomorphological terminology and principal dynamic zones. 4 > B R E A K E R t S U R F I S W A S H I P R I N C I P A L D Y N A M I C Z O N E S ------------------- HE A R S H O R E - ----------------------------- B E A C H OR S H O R E -------------- - I C O A S T O F F S H O R E — I N S H O R E ► U F O R E S H O R E ---------- ► ! - . — B A C K S H O R E — - M H H W - M H W dunes berms MLW - M L L W - trough S H O R E F A C E bar ridge B E A C H FACE BACK BE A CH T R A N S I T I O N still water level plunge point C O A S T A L A R E A G E O M O R P H O L O G Y The principal dynamic zones (Pig. 1) of the coastal water system are the breaker, surf, transition, and swash zones. The breaker zone is that area where the swell and wind waves become unstable and the wave form collapses resulting in surf. The water motion in this area changes from essentially oscillatory to transillatory. The surf zone extends from the seaward limit of the backwash to the breaker zone (Ingle, 1966). This zone includes the secondary and tertiary breakers and 1b usually covered in part with foam. The presence and especially the width of the surf zone is primarily a function of tidal phase and beach slope. The surf zone is regarded by many (CERC, 1966) to Include the whole coastal zone from the beginning of wave Instability to the limit of the uprush. The transition zone is the very narrow zone of high turbulence where the leading edge of the surf plows into the backwash (Schiffman, 1965). fhe swash zone is the area of the beach alternately under water during the wave uprush and dry after the backwash. Measurement Units Within the scientific community measurements are usually reported in the metric system. Engineers and the American public use the English system. Comparison be tween these systems is possible if burdensome. Yet pre sentation in one system or another is not always desirable. Thus, tidal elevations in this country are always reported in feet whereas grain diameters are seldom shown in inches hut rather their decimal equivalent or the derived ^ intervals or sieve mesh openings. Therefore, in this re port, fully cognizant of the Internal inconsistency, both the English and the metric systems will be used in juxta position. Whenever parts of the almometer, tides or larger distances are mentioned they will be in Inches, feet or miles. Smaller distances such as height of sand movement and sand sizes will be in metric units. Sediment Movement Sediment moves either along the bottom and in fre quent contact with it or through the water with only Intermittent contact with the substrate. The former is the bedload, the latter the suspended load or suspended sedi ment. Einstein's (1950) definition of bedload averaging only 2 grain diameters is too restrictive for field usage. It is almost Impossible to attain such precision of measurement. An accepted definition of suspended sediment is sediment which remains in suspension for a considerable period of time (Univ. of Iowa Hydraulic Lab., 1940). If and when the entire motion of sand particles is such that they are surrounded by water, they are said to move in suspension. One criterion for suspension is that the settling tendency of the solid particles due to their weight is counterbalanced by the water's turbulent veloc ity. In true suspension there is no slip between the fluid and the grains. The sediment moves wherever the fluid flows. The upper limit where suspension ceases is the water surface; its lower limit Is extremely poorly de fined. Close to the bed it becomes difficult to fulfill the requirements for suspension. The transition between suspended and bedload is gradual and continuous. Sand be ing part of the suspended load at one time may a short while later be a part of the bedload and vice versa. Therefore, by operational definition, in this re port any observed sediment movement rising above the bottom more than 10 cm or remaining in suspension for more than 3 sec will be called suspended sediment. At this height above the bottom there is a break between frequent and only intermittent sediment movement. All other sediment move ment closer to the substrate is assumed to be by rolling, creeping or saltation. In this inertia movement (Bagnold, 1954, 1956; SanderB, 1965) sediment moves differentially within the water and follows, as seen from above, linear paths. List of Symbols A cross-sectional area A* constant arbitrary distance from the bottom constant concentration by volume wave celerity depth of flow particle diameter efficiency of bedload transport efficiency of suspended load transport bedload rate in weight per unit time and unit width suspended rate in weight per unit time and unit width wave height breaker height water depth integral values dynamic transport rate of sediment fraction of bedload in a given grain size fraction of suspended load in a given grain size von Kantian's constant Nikuradse sand roughness k^ constants wave length mean particle diameter probability of a grain being eroded hydraulic radius due to sediment particle energy gradient due to slope time flow velocity fluctuation in flow velocity friction of shear velocity, measure of intensity of turbulent fluctuation shear velocity due to grains only settling velocity of grains weight of sediment vertical distance from a reference level exponent in suspension distribution = ^ss fc u* angle between wave orthogonal and normal to the coast relative wave height H/h, specific weight corrective value diffusion coefficient variability factor of lift wavelength of bedform single step of bedload measured in grain diameter units density effective density of sediment grains fluid shear stress exerted at bed boundary intensity of bedload transport intensity of transport of individual grain size V . to Data Storage For this report five data curves were gathered every 1/5 of a second for 10 days (three almometers, staircase and clock). Wind direction and velocity were recorded continuously. Sea state (breaker height and period, direction of wave approach limit of swash uprush and swash temperature) and sediment samples were collected every two hours. The over 22 x 10® pieces of information gathered is too bulky to be physically incorporated in this report. Therefore, only the salient facts will be summarized. The analogue magnetic tapes and computer printouts of all the data are on file in the Department of Geological Sciences at the University of Southern Cali fornia. Acknowledgments Any investigation requiring the construction of new equipment and its continuous monitoring requires the sup port of many individuals. Mr. Craig Todd was indispensable in fabricating the electronic parts and accouterments. Mr. John Wilson made the waterproof housing and underwater connectors. Some of the underwater cable was obtained 11 P — p intensity of shear = ^ S — —r—r e available power attributable to unit boundary area 12 ; through the courtesy of Mr. Edwin C. Buffington of the U. S. Navy Underwater Warfare Center and Mr. Steven Warnee of the U. S. Army Coastal Engineering Research Center and Mr. Frank Agapoff of the U. S. Navy. Dr. James W. Vernon of General Oceanographies, Inc. provided generous use of his facilities. The U. S. Navy through its Pacific Missile Range at Point Mugu, California provided trailers, record ing facilities for the field tests and almost unlimited computer time. The work of Messrs. Frank Agapoff, Lee Dis- brow, Del Pierce, and Clifford LeMieux is appreciated. Dr. Bonn Gorsline, Chairman of the writer's commit tee, gave freely of his time and made many helpful sug gestions during the progress of this study. The Guidance Committee consisting of Drs. Donn Gorsline, Robert Os borne and Richard Tibby as well as Dr. Ronald Kolpack critically reviewed the manuscript. The writer is indebted to the many students, academi cians and friends who assisted during this study. To Michael Carruth, Robert Clover, Leon Hooper, Donald Mathews, John Paris, Robert Young, Ronald Zakrzewski, Alfred Zukor and especially Terrence Koch, grateful thanks. The project was generously supported by grants from the National Science Foundation, GA22842 and GB6319, the Office of Naval Research, NONR(6)-00013-72 and N00014-67-A- 0269-00090, and the Geological Society of America, 1480- 71. SEDIMENT MOVEMENT State of the Art No comprehensive theory has been developed on the mechanics of sand movement within the breaker, surf and swash zones except for transport parallel to shore (see among others, Putnam, Munk and Traylor, 194-9; Savage, 1962; Brebner and Kamphuis, 1963; Galvin, 1967; Sonu, McCloy and McArthur, 1967; Komar, 1969; and Thornton, 1971). Much work, however, has been done on stream sedi ment transport. This has been summarized by Graf (1971). There are three slightly different approaches to the formulation of a bedload equation. The first con siders the shear stress relationships based on the work by DuBoys (1879) and amplified by O'Brien and Rindlaub (1934), Shields (1936) and Kalinske (194-7). The second following the work of Schoklitsh (1930) considers dis charge relationships. Meyer-Peter1 s and others' (1934-, 1948) equations have much the same form. The last and most commonly used formulations are those of Einstein (1942, 1950, 1964) who considers the statistical operation of lift forces. Bagnold (1941, 1946) and Colby (1964) follow in the same vein. Einstein's work should be 13 14; directly applicable to the surf zone for he states that bedload transport Is related to fluctuations In velocity rather than the average velocity and the definition that a critical value for initiation of sediment motion is Impos sible, therefore should be avoided. Geologists are familiar with H^ulstrom's (1939) threshold criterion diagram, those of Postma (1967) and the ones summarized by Stone and Summers (1972). These must be used gingerly especially in the surf zone. The diagrams are based on the logarithmic velocity profile expressed by the dimensionless parameter u = 8.5 + 2.3 log a . It has u# “k S' been shown (Briggs and Middleton, 1965) that it is not the average velocity but the shear velocity that 1b the criti cal factor and that they are not directly proportional to each other even for constant bottom roughness. Furthermore the ratio u depends on the height at which u was measured, u# Hence if the surface current velocities are measured, the depth of the water column is crucial. Also, as will be seen, the k value does not stay constant as the sediment concentration increases. To avoid a threshold criterion Einstein develops his bedload equation in another way. If there is deposi tion a particle of diameter d will be deposited a distance A-^d away (see list of symbols for definition of terms). If g^ is the bedload rate of movement per unit time and 3 l|j is a particular size fraction and ifykgd "^e weight !5 of a single grain, the total deposited per unit width and time is _ * _ (M ) (et **&-*) C A u W * eb If there is erosion and if i^ is a fraction of bedload of a given grain size, then the number of grains d in a unit area is ^b . If p is the probability of removal per 2 kxd e I, p unit time and area is b ; tQ should be dependent on kid2te the settling velocity ^ f l A0 . If there is N f ' ^ c c L - e ) equilibrium and deposition is balanced by erosion, the bedload formula is A l Kz ^ V r, K, m < ce Einstein concludes that p may be used to calculate the distance traveled (A,d). If p Is small the travel i t distance is a virtual constant (A-^d = ^pd). If p Is large only (1-p) grains have a chance to be deposited in x^d distance while p grains stay in motion. Of these, p(l-p) grains are deposited after going 2X^ 6. distance but p2 grains are still not deposited. And so forth. Thus a series can approximate the total distance traveled: A l4 -- £ 0-?)?" O't+i) Introducing this in the previous equation and separating p slves! If i - j b e W N i 16 «J . . and A.t s VCiK-j then e ^ - e The probability of erosion also depends on hydrodynamic lift and effective grain weight. If ^ is the effective weight which is a function of the hydraulic radius with respect to grains and if is the lift function deter mined experimentally on a scale of then the probability for motion becomes according to the normal error law: S j j f C e‘ i - t 4 - H Suspended Sediment Rouse (1937» 1964) worked out a derivation for the vertical suspended load distribution based on the dif fusion dispersion process such that =. ( ? =: This equation can be used to calculate the concentration of a given grain size at any distance y from the bed if a reference concentration C at a distance a a above the bed is known. This equation can be integrated over the region where suspended load occurs, from a to P so that g0 = T where 0 and u are functions of y and g0. Thls^ls the suspended load rate in weight per unit time and width. This equation is limited for it can predict the relative concentration in the vertical but not its absolute value (Einstein and Abel-Aal, 1972). Further IT work by Vanonl (194-1, 1946, 1963) shows, moreover, that in the presence of sediment the k constant used to calculate z decreases rapidly. This prompted Einstein (1950) and Einstein and Ohien (1954) to express the velocity with the 11 ‘ 68 = gration indicated is impossible but numerical itteration for various a/d and z values gives two graphical values The ultimate goal of the equations is to be used to predict the amount of sediment moved in natural conditions. This is extremely difficult, for each of the equations relies on the experimental determination of its coef ficients. These are usually obtained in laboratory flumes with uniform grain sizes. Therefore, application to field studies pose many unsolved problems. Theoretically the addition of suspension and bedload formula should give the total sediment load. Unfortunately, using the different equations for bedload and Einstein's suspended sediment equation give discrepancies for the same data of over 100 percent (Graf, 1971). BagnoId (1963» 1966) has approached the sediment transport problem somewhat differently. He argues ef fectively that it is the existence of lifting forces equal to the immersed weight of the sand that is paramount in Cr? sediment transport studies. The immersed weight m'g The inte- and I2 so that 18 , therefore the total load transported per unit width 1 is jL-xt+is ^ Vk Us This dynamic transport rate can be converted to a work rate if the bedload fraction is multiplied by the coef ficient of solid friction* tancC , and the suspended load by U^/us . This yields ife+ls - ™ The available energy in the water to transport sediment is . This assumes any energy losses are due solely to fluid drag on the bottom. If the power expended in transporting bedload is e^ the remaining power (1-e^) is available to maintain the suspended load. If e_ Is the suspension efficiency, the s 1 • total transport rate can be written as J L = = 00 F £i p e& C) ' From flume studies es(i-e^) = 0.01 and us = u for true suspensions. There- fore, i= CO 3 The total load can be obtained if these four parameters are known. Sand Movement Normal to the Coast Three theories have been proposed to explain sand movement normal to the coast. One theory is based on the neutral line (null point) concept proposed by Cornaglia (1881, 1891; Beach Erosion Board, 1950; or Vollbrecht1s, 1954 exposition is more readily available). The theory states that there are two opposing forces acting on sedi ment in shallow water: (l) the onshore wave drift and (2) the offshore gravitational force produced by the "bottom slope. For each grain of given density, size and shape there exists a line of equilibrium between these forces for on and offshore motion. The larger or denser the particle, the closer to shore is its null point. Shoreward of this line the particle will move onshore, offshore of It seawards. It must be remembered, however, that this theory applies only to bedload movement on a constant slope in relatively deep water (see Vernon, 1966). Cornaglia (1881) suggested that this line, with the conditions existing in Italy, is at a depth of 33 ft. Timmermans (1935) suggested the depth to be 2.5 times greater than the wave height. Experimental work by Ippen and Eagleson (1955), Eagleson, Dean and Peralta (1957) and Eagleson, Glenne and Dracup (1961) has concentrated on this theory. Ippen and Eagleson (1955) give the relations determining the position of the null point as (H/h2) (L/H) (c/w) = 11.6 for a model beach (slope = 1:15; (H/L = 0.01-0.08). Yet they conclude that "in general the net transport . . . due to the type of sediment motion under discussion must be in the shoreward direction" (p. 78). This is precisely the view of those who believe that the inequality of onshore over offshore orbital velocities of waves causes all the sand to be transported toward the beach. Only the different wave parameters are Important in determining the quantity of sand transported. Shepard, Emery and LaFond (194-1) and Grant (194-3) believe that this shoreward sediment movement is balanced by sediment-laden rip currents and to a minor extent undertow. On the other hand, Keulegan (1948) and Munk (1949) suggest that rip currents are not essential to the seaward motion of grains. Miller and Zeigler (1958, 1964) tested this concept in the field and found fair agreement between observed and movement predicted by the velocity profile suggested by Longuet-Higgens (1953) and Ippen and Eagleson (1955); namely, a shoreward movement of all grains along the bot tom, entralnment of fine grains in the breaker and their seaward transport at middepth in the return flow. More recently, investigators (Murray, 1966, 1967, 1970; Inman and others, 1971) have become aware of the great importance of diffusion of suspended sand in the distribution of sediment. Nagata (1961, 1964) reports that the onshore transport of suspended sediment is only a third of the offshore transport on a Bteeply sloping beach whereas they are equal if the beach slopes gently. Many laboratory studies have been conducted to determine the effect of wave, tide and sand character istics on the rate of sand transport and the establishment of equilibrium beaches. As early as 1928 Kressner found that the steepness of a foreshore and offshore slope pro duced by waves of given parameters increases with the Bize of the sand but decreases as the size of the waves in 21 creases. Varying the wave period over different sand sizes seems to lead to lesser amounts of sand being trans ported compared with constant period tests while leaving the slope virtually unchanged (Watts, 1954). Many authors (Saville, 1950; Johnson and Shay, 1950; Scott, 1954) have confirmed Meyer*s (1936) observa tion that wave steepness is perhaps the most important variable in determining the submarine slope. The steeper the waves, of the same energy, the more gentle the whole slope. Saville (1950) working with sand of 0.03 mm diameter, divided beach profiles into two categories; storm profiles are caused by waves with a steepness greater than 0.03 and ordinary profiles are formed by waves less than 0.025 steep, with a transition zone in between. On a storm beach sand is moved from the beach face to form a bar. With waves less steep the bar gradually moves on shore and the sand is spread out over the beach. Johnson (194-9) gives the transition zone from 0.06 to 0.02, But Gugnyaev (1954) found that waves Bteeper than 0.005 formed a bar. He notes that the bar aggrandizes from both the offshore and onshore directions. The many tests carried out in Cambridge (King and Williams, 1949; King, 1959) show the differences of sand displacement on both sides of the breaker zone. Offshore the sand moves shoreward no matter what the wave condi tions. This movement is intensified the greater the wave 22 height and period but is little effected by changes in steepness. On the foreshore wave steepness is considered to be of the greatest importance. When the wave steepness increases, the shoreward movement of sand decreases and even reverses. Rector (1954-) provides an empirical limit ing relationship between the sand Bize and wave steepness: Md/L = 0.0146 H/Ii^*2^. When the ratio of diameter to wave length is greater than the steepness side of the equation, sand moves from the offshore to the foreshore. When the ratio is small, the reverse is true. Sonu and van Beek (1971) recently determined that a period of growing waves has more pronounced effects in determining accretion than the actual steepness. Whereas a period of wave decay leads to erosion. Harrison (1969) using data from a time series, of 26 days, on a Virginia beach response to 27 variables (Harrison and others, 1968) found the beBt-flve predictor equation for the amount of sand moved on the lower foreshore measured at low tide to be: Q = 5.80 - 113.15 (Hb/gT2)1//2 - 52.11(hh/r)^0 -7.27 W 6mQ + 2.72(d/£6<0 - 35 (f f l )x2.0 hh = hydraulic head, the vertical distance between water table outcrop and wave trough r = runup or distance to breaker z = average trough to bottom distance in front of break ing wave 23 m = mean slope of foreshore subscripts = time in hours when the maximum influence on the amount of sand movement is felt Note that the correlation of hydraulic head/distance to the breaker zone to the amount of sediment moved is nega tive and its influence is strongest at mid-ebb tide. Its correlation coefficient is only slightly less than that for the wave parameter. Depth of Water for Sediment Movement The depth of water where sediment movement becomes appreciable is difficult to ascertain. In Airy's wave theory waves first feel bottom when the depth Is equal to half the wave height. Yet, Arthur (in Shepard, 1963) has shown that down to depths equal to 1/4 the wave height the change In bottom phase velocity is only 0.37 percent, so only at much shallower depths does any appreciable amount of sand transportation take place. Inman and Rusnak (1956) in detailed surveys of the La Jolla shelf found a maximum change of 0.15 ft in topography over a 40-month period. Trask (1955) divides the sea floor off southern California promontories into five regions; below 60 ft is a passive zone of little or no movement, from 60-30 ft an inter mediate zone in which sand moves at Intervals, an active zone extends from 30 ft to the surf zone and lastly the surf and beach zones. Vernon (1966) using fluorescent tracers off many southern California beaches found that with 1.5 ft waves essential movement of 0.25 mm sand stops below 40 ft and of 0.42 mm below 30 ft. If the waves are 2.5 ft these depths are increased by approximately 10 ft. Even more stringent conditions are imposed by Inose and Shiraiskl (1956). They report that sand with median diameter of 0.13 mm begins to move at 18 ft only when the wave height exceeds 5-8 ft. Depth of Sand Movement The depth to which sediment is moved in the fore shore and nearshore zones is discussed by King (1951)- She found erosion depths to be 3-4 percent of the breaker height. For every foot increase in breaker height, the depth of sand disturbed increases by a cm. This holds for the whole inshore and foreshore zones with no Increase noted under the breaker zone. Otvos (1965) working in Connecticut found values of 20-40 percent and frequently higher, up to 200 percent. Williams (1971) working in Hong Kong concurs with the values of Otvos. Suspended Sediment Accurately measuring the amount of sediment in suspension is difficult indeed. Until recently few direct methods existed whereby the instantaneous suspended sedi ment load of the water column could be determined. Most of 25 the numerous types of samplers are for use only in a uni directional stream flow (U. S. Interagency Committee on Water Resources, 1963; Univ. of Iowa, 1970) or average the concentration over a number of wave cycles or units of time (Inman, 194-9; Watts, 1953; Nagata, 1961; Cook, 1970) or integrate the volume over depth (Federal Interagency Sedimentation Project, 1970). One of the most Interesting experiments in measur ing suspended sediments in the laboratory was conducted at the University of Tokyo (Homma, Horikawa and Kajima, 1965). They used photo-transistors to measure concentration at different heights above ripple crests and troughs. Close to the bottom the concentration of suspended material in creases dramatically not only under the crests of waves but peaks at least three other times during the wave period. This correlation of suspended load with wave phase decreases gradually as the distance from the bottom Increases. Hattori (1969)* however, by recording the change in resistance between electrodes as sediment passes between them found that the vertical distribution at the nodes of standing waves is independent of wave characteristics. The results of the many field studies are difficult to compare due to diverse sampling methods, varied wave conditions, bottom configurations, sediment sizes and variance in reporting results. Tests by the Beach Erosion Board (1933) at Long Branch, New Jersey using brass can- nisters show that only near the breaking point of the waves does the amount of sand moved in suspension reach 17 gm/l or 5 percent of the total load. Twenty-six feet seaward of the breakpoint this had fallen to only 4 gm/l. On the shoreward side the decrease was even more rapid. Marlette (1954), Curtis (1963) and Rudolfo (1964) used 500 ml bottles to take samples in the foreshore at the water's surface, mid-depth and 30 cm above the bottom. The results show that the weight of 4 replicates taken over 3 hours increases from 0.05 to 40 gms in the swash zone. Little (1968) using mason Jars shows the highest concentra tion reported anywhere in the literature of 79.5 gm/l in the transition zone. The average values he reports are 1:2:4 for the plunge surf and swash zones, respectively. Aibulatov (1966) averaging many samples gathered by a series of bottles lowered from a specially constructed cable car at Anapa on the Black Sea clearly shows the ef fects of ridges and bars on the sediment concentration. Inman (1949), Terry (1951), Homma, Horikawa and Sonu (I960) and Nagata (1961, 1963) placed multisock sedi ment traps in the surf zone. Nagata reports that there are greater concentrations in the plunge zone in the sea ward direction if the beach is steep whereas the opposite is true If the beach gradient is gentle. Homma, Horikawa and Sonu placed multidirectional 0.075 mm mesh traps in 27 the nearshore zone In two small “ bights. In the breaker zone there Is a sharp decrease in sediment trapped as the height above the bottom Increases (30 gms at Katase, 200 gms at Kamakura). In the surf zone 70 gms was collected at both sites near the bottom which decreases to 60 gms at Katase and increases to 450 gms at Kamakura near the top. Pukushima and MIzoguchi (1958) placed 16.4 ft bamboo poles with 5 cm holes cut between the Joints in the surf zone giving an Integrated sample of 17 positions. Outside the breaker zone suspended load is relatively small but particles reach 4.9 ft above the bottom. In the breaker zone the bottom samplers caught 233 gms but above about 3 ft no sediment was collected. In the surf zone the peak is blmodal showing a larger peak about 3 ft above the bottom (203 vs 194 gms). Watts (1953) utilizing a suction pump held in a vertical position took many samples of 5-minute duration at different depths in the surf zone off the pier at Mission Bay, California. The greatest volume (7*9 gm/l) was found Just shoreward of the plunge point 20 cm from the bottom in waves 3 ft high, but only one sample was taken In the transition or swash zones. Fairchild (1971) using a similar device at Tentnor, New Jersey found 0.025 - 2.6 gm/l in the surf zone with breakers 1-3 ft high. The con centration peaked at a breaker to depth ratio of 0.8. It decreased rapidly seaward and more slowly landward. He 28: reports that the concentration tended to decrease upwards in the water column but that there was much scatter. The size of the suspended sand was essentially constant with elevation. It is interesting to note that Fairchild (1956) using a similar arrangement except that the nozzle was horizontal and the experiments were done in a flume re ports that the colder the water the higher the suspended sediment concentration. THE ALMOMETER General Statement The principle that the presence of sand particles in water makes it less transparent and could be measured was recognized quite some time ago. Shelford and Gail (1922) and Kaletin (1923, in Jakuschoff, 1932) were the first to design various devices with a light emitting source located opposite a photocell to measure sediment concentration in water. Since then many others, Jakus- choff (1932), Petterson (1934-), U. S. Interagency on water resources (1963), Jerlov (1968) and Drake (1972), have used this principle, longinov in a little known article (1968) was the first to use photoelectric cells to measure suspended sediment concentration in the nearshore zone. All of the devices used measure concentration at a given point per unit time. The almometer can measure the distribution throughout the water column simultaneously. The Almometer The word almometer is derived from two Latin words, alveus (fluminis alveo; Aenied 7,33) and motus plus meter. It consists of two parts (Fig. 2), a light source and a 29 Figure 2 Top: Bottom: The almometer, consisting of two parts, a high intensity light source and a series of photo-electric cells both encased in watertight acrylic cylinders. Tvo circuit boards of the almometer. The bottom one contains 8 photo electric cells. Six of this type (2 cm between photocells) and one with 16 photocells (1 cm between photo cells) were placed together with the top board in each almometer. The top circuit board contains 8 Integrated circuits and ancillary electronics to interface on and offshore components. 30 32 group of light sensors. These are encased in separate water-tight acrylic cylinders and attached to metal poles which are anchored some distance apart in the substrate. The light source is a super high intensity 48*' cool white fluorescent lamp (F48T10/cw) with an average life rated at 9000 hours and a top initial brilliance of 6000 lumens peaking at 5500 S. The lamp is secured by two Hagh output sockets, one of which is spring loaded and enclosed in a 2^" outside diameter (o.d.) l/4" wall 50" long plexi glass tube. Although the lamp is only l£" in diameter, the 2" interior diameter (i.d.) of the enclosing tube is required to prevent breakage during the flexing of the tube under wave impact. This tube is capped on both sides by a 1" thick acrylic plug. The bottom one is cemented in place while the top is removable and is sealed by double "o" rings. The top is secured and the whole tube is pro tected from rocks and flotsam by four 3/16" stainless steel rods threaded on both sides and tightened by stain less steel nuts. The tube has four two-piece plexiglass mounts which surround it and the anchoring pipe. These mounts are fastened by 2^" stainless steel hex screws. This allows easy field installation once the pipe has been secured. A water proof bulkhead was made to accommodate the 5/8" thick 00-05 HOP (5/12) S J0835, 5-conductor 12-gauge heavy duty flexible styrene butadiene rubber cable. A 2" thick 4" long PolyVinyl Chloride (PVC) cylindrical stock was drilled to fit the cable snugly. One side was in dented, fitted with an "o" ring and the final l" threaded externally to fit into the top cap of the lamp housing. The other side was hollowed out, cambered 50° and the last part threaded internally. Into this opening was placed a doubly cambered hollowed out rubber stopper which was tightened by an externally threaded 1 l/4" thick l£" long PVC hex stock. This squeezing of the rubber against the cable is an effective water block. To insure water tight Integrity the outside of the whole bulkhead was taped with Scotch Electrical Tape #23 and sealed with Skotchkote Electrical Coating. This assembly proved to be a very in expensive but efficient combination cable termination and bulkhead. On shore two 944LH and two 949UH Universal 1500 ma ballasts were placed in a t ! coffin" (Pig. 5). This pro vided the capability for utilizing up to 6 fluorescent tubes in any combination. The other part of the almometer consists of a plexiglass tube containing 64 photo-electric cells and requisite circuitry (Pig. 3). The photo-electric cells (Clairex CL905HL) are composed of cadmium sulfide and are of the photoconductive bulk effect type. Therefore, the entire surface of the cell acts like a variable resistor. The cell decreases in resistance as the light level in creases. The darker the surface of the cell, the higher Top: Bottom: Figure 3 Emplacement of the almometer on the lower beachface. Almometer stations across the beach at Pt. Mugu. 34 36 the resistance. A photoconductor cell is used rather than a photovoltaic or photoemmisive one because of its 10^ to 10^ greater sensitivity to light. Photodiodes and photo transistors have a faster response time than photo conductors but are relatively insensitive to changes in the outer light limits. The absolute value of the resistance depends on the specific light level, its spectral composition and hyster esis. The cell used has the following characteristics: Table 1. Response time versiis light Intensity of photo electric cell CL905HL (Clairex, 1966) Poot Candles 0.01 0.1 1 10 100 Rise Time (sec)* 1.460 0.116 0.030 0.005 0.002 Decaytime (sec)* 0.159 0.019 0.004 0.002 0.001 Resistance** 21.5M 1.7M 180K 150 3 Peak Response: 5500 £; Diameter: 0.53 cm * Time to 91-l/e of final reading after 5 sec dark adaption. ** In the present mode of utilization with a potential of 5 volts and 22M resistance. The photoelectric cells are arranged on seven 2.5 x 16 cm circuit boards (Pig. 2) so that from bottom to top 8 cells are 2 cm apart, 16 cells 1 cm and 40 cells 2 cm apart. The packing density was regulated by the binary address logic, the length of the fluorescent lamp and maxi- Figure 4 Top: Bottom: Rotating the steel pipes out of the sand for the lower beach face almometer. The almometer and a wave height measurement device on top of the berm crest. 37 39 mum resolution at the sediraent-water interface. Each group of 8 photoelectric cells is connected to a Sili- conix SI 3705-193K and 8 channel Mos switch with decode driver (see Appendix I). At the very top is a 2.5 x 23*8 cm circuit board with 2 voltage regulators, a voltage invertor, two one- shots, two binary counters, a binary l-of-10 decoder and an output amplifier integrated circuit. Figure His a schematic of all the circuitry in the almometer. An ex planation of this is better relegated to an appendix (II). From shore a 7/16" thick neoprene control cable with eight 18 gauge leads provides two clock pulses (Y and Z), +20 volts, -20 volts, +10 volts, + signal and - signal (ground). These cables are secured by a Glenair GL30L8- and a Glenair GL30L8-BC cable termination and bulk head connector. The latter is screwed into the acrylic cap of the plexiglass tube. The assembly of this tube is similar to the one containing the fluorescent lamp. The only dif ference is that this tube is only lV o.d., l" l.d. and .57'* long. It was painted black except for a 0.6 cm strip facing the photoelectric cells. This cuts the light scattering due to the sun. Both of these tubes (Fig. 4) were anchored in the sand by 131 long l" o.d., 3/16" wall seamless steel pipe. To 6" from one end a 5" circular steel plate, bored through the center and split with the two edges separated 40 l£", was welded making a one lip auger which, was rotated into the sand to a depth of 6 ft. A Verorack System 3A formed the bases for the inter face of onshore and offshore electronics. It holds 8 plug boards (see Appendix I) containing a +5v power supply, a clock module, 3 modules containing logarithmic amplifiers and line drivers, a display selector and a display digital to analogue convertor plus all the cable receptacles, re quisite fuses (2 for each almometer) and BHC output Jacks. Pour power supplies were used to drive the various com ponents, two Harrison Laboratories 800 B-2 for + and - 20 volts, a Trygon Electronics MS 36-10 AMOV for + 10 volts and an Elasco Eastern LIC5-3A for + 5 volts. Inside the Pacific Missile Range Special Measure ments Van (Pig. 5) the incoming data was monitored on a Hewlet Packard oscilloscope (130C) (Pig. 5) and recorded on two Precision Instrument Series 200 half-inch seven track magnetic recorders. The use of two recorders al lowed continual recording insofar as one recorded while the tape could be changed on the other. The recordings were made at 1-7/8 inches per second so that a 2500 ft reel lasted 4 hours and 20 minutes. On the seven channels were recorded a 500 Hz clock, staircase, CERC wave gauge, swash height staff and the output from three almometers. The first channel was recorded directly while the others were in a frequency modulation (fm) mode with a center Figure 5 Page 1 Top: The Pacific Missile Range Special Measurements Van and living quarters. Bottom: The inside of the Special Measurements Van with the tape re corders, power supplies and on shore and offshore interface systems. Page 2 Top: The monitoring oscilloscope and modules containing the power supply, clock, logarithmic amplifiers, d/a convertors, a diode water height display. Bottom: Four 1500 ma ballasts and cables leading to the fluorescent lamps offshore. 41 42 PACIFIC M IS S IL E R A N G E 9 K I J U M a S t H E M E i n V A N O H D 'iA K C I . D I V I S I O N c a i m j 44 frequency of 1688Hz. Calibration Calibration of the photoelectric cells was ac complished by stirring up a sand and water mixture inside a glass jar and measuring the suspended concentration. Into a one-foot diameter circular pyrex battery jar t 1000 gms of sand from the middle foreshore of Point Mugu beach was placed. To this was added 12 liters of sea water at 24°C. The mixture was agitated by two Universal Electric motors rated at 2000 rpm. These were connected to a rheostat to regulate the actual revolutions. To one- foot shafts were fitted l£” triangular plates, 3/16” of each end twisted up so that the camber of the leading edge was 45° dominishing to nothing at the trailing edge. Ex perimentation has shown that this design when placed 3” from the side of the jar produced the most even distribu tion of suspended sediment with a minimum of whirlpools and surface agitation. The amount of sediment stirred up could be regulated by varying the proximity of the "pro- pellors” to the sand surface and their revolutions. In the quadrants opposite the motors, just outside of the battery jar, a P48Tlo/cw fluorescent bulb was plac ed on one side and a photoelectric cell (CL905HL) on the other. The cell was wired just as in the almometer (see schematic in Appendix I). The increase in voltage when the 45 resistance of the photocell increased as more and more sediment was stirred up was measured on a Triplett VOM (800) volt meter. The actual amount of sand in suspension was measured by drawing approximately a liter of water and sand mixture with a 1 cm i.d. hard rubber tube connected to a Gast vacuum pump with a maximum 614 cm^/sec capacity (see Fig. 6). In a calibration run the motors were started and the photocell placed to obtain a desired voltage. After a minute wait to insure stability of voltage readings and overcome the hysteresis effect, the vacuum pump was started until a vacuum of 27" of Hg existed. Then the rubber hose was introduced into the water to the height of the photo cell, unplugged and a sample taken. Different runs were made at various distances from the glass wall. After a run the amount of water and sediment inspired was -measured. The sand was then washed through a 62ja screen, dried, weighed and equalized to a liter of water. Figure 7 shows the calibration curve fitted to 170 samples. The curve is a growth curve fitted by the finite difference and selected points method outlined by Hoerl (1954). The equation that best approximated the data is: Voltage = 4.78 - e0'699 gm/1 of ailment Various sources contribute to the spread of the data points. Perhaps the greatest source of variance is Figure 6 Setup for the calibration of the photo electric cells. 46 Figure 7 Calibration curve of photoelectric cell CL905HL. 48 + * > VOLTS photo cell I 00 +01 opaque g r a i n s 200 800 700 900 100 300 500 600 4 00 GRAMS PER LITER the difference between photoelectric cells. Three photo cells were used to establish the calibration. The CL905HL photoelectric cell has a tolerance up to t 33 percent of the specified resistance at a given voltage (Clairex, 1966). Another source of error is the fluctuation of the amount of sand in suspension due to unequal distribution of sand within the Jar. As can be seen in Table 2, the standard deviation of the amount of sand in suspension in creases. But 6* as a percentage of x stays around 25 per cent (19, 25, 25) in the first three columns and decreases dramatically to 2 percent in the fourth column. The 4.9 v readings were taken by submerging the rubber hose directly into solid sand. The fifth column shows the pump stability operating at almost 2 atmospheres. Since the sampling runs lasted between 2.3 and 3*5 seconds, a minor error is intro duced by this fluctuation. The relation between the amount of sand actually in suspension and what was measured is difficult to ascer tain. Watts (1953) by careful study determined that a l/2" vertically disposed nozzle with an intake velocity ap proximately twice the maximum orbital current velocity is within 15 percent of the true suspension. And he used sand of 0.53 mm mean diameter:. - So it is assumed that a 1 cm nozzle pumping at 300 ml/sec using sand of 0.16 mm mean diameter should also be within 15 percent of the actual suspensates. 51 Table 2. Fluctuations in the amount of sand and water inspired during the calibration of the photo electric cells (gins/liter) Voltage 0.1510.04 1 15.55 2 18.13 3 17.40 4 26.14 5 17.79 6 24.34 7 18.03 8 23.66 9 10.68 10 12.29 X 20.18 3.38 .0*0.10 3.0±0.20 73-86 140.38 52.38 110.24 58.64 98.60 68.91 52.37 78.86 86.39 51.27 97.81 99.52 115.55 41.49 108.14 68.35 123.87 79.42 73.46 67.27 100.68 16.95 25-33 4.9*0.05 ml/sec 904.46 310.94 896.20 294.83 858.89 302.65 886.73 305.67 891.28 298.31 308.34 295.16 296.39 304.59 301.12 887.51 300.40 15.47 5.81 52 To determine the effect of grain size on the voltage readings, ten runs were made with each sand of 0.73> 0.45, 0.09 mm mean diameter. With the coarse and medium sands results indicate that their distribution is similar to the fine sand calibration curve. The very fine sand curve is shifted to the left so that more sand is needed to reach a given voltage. This is probably due to the increase in light scattering surfaces present. Sediment composition also affects the voltage level. No matter how much fine pure quartz sand is in suspension the voltage obtained does not surpass 1.0 volts. On the other hand, a fine sand composed only of heavy mineral grains yields concentrations at the lower voltage levels about. 30 percent less than those obtained by fine mixed sands. At higher concentrations their effect on voltage is about the same as mixed sands. Outside of either these translucent or opaque extremes any mixture likely to be encountered on beaches renders approximately equivalent results. The amount of fine sand composed of 50 percent quartz and 50 percent heavy mineral grains which gives a 1 volt reading 1b 75 gm/l 1 10 percent. A mixture of 35 percent quartz, 75 percent heavy minerals yields 80 gms/l i 10 percent, while 75 percent quartz and 25 percent he avies gives 65 gm/l 1 10 percent. There is one drawback in using a jar in the calibra tion; light is scattered within the glass. This caused voltage readings to be lower than they should be if no sand 1b stirred up. Thus 4 cm below the sand surface Is necessary before the cell registers a total darkness volt age. Whereas 2 cm are needed to give the same reading if the cell is immersed directly into dry sand. However, certainly part of the difference is due to the translucency of the interstitial water. This divergence between actual and measured sand levels disappears somewhat when the sand is stirred up. Then the sand in motion blocks most of the light reaching the side of the Jar around the photocell so that the scattering effect is diminished. This effect was overcome by painting the almometer black. Yet even more important is the attenuation of light in the water itself due to the increase in sand in suspension. There is no plausible way to overcome this effect. POINT MJGU, CALIFORNIA General Statement Three almometers were emplaced from September 28 to October 8, 1971 in a line perpendicular to the shoreline on the beach and shore face of the Arnold Road Beach at the U. S. Navy Pacific Missile Range in Point Mugu, Cali fornia (see Fig. 8). This location presents some desirable attributes. The shoreline, here, is essentially straight trending N 50° W for over four miles. The site is midway between Mugu and Hueneme submarine canyons. Since these canyons are so close to shore they drastically reduce the longshore transport of sand. The U. S. Army Corps of Engineers Experimental Groin located 750 ft to the west blocks most of the local longshore sand transport. The area is on a military base and therefore is secured obviating any espieglerle. Electrical power and IRIG (Inter-Range Instrumental Group) timing is available at the water's edge. The U. S. Navy kindly provided lodging and recording facilities. The U. S. Army Corps of Engineers maintain a deep water wave station and tide gauging station here. The Corps also conducted a Radioactive Isotope Sand Tracing (RIST) experiment at this locale just before the 54 Figure 8 Location sketch map of Arnold Road Beach at Point Mugu, California. 55 PORT HUENEME MILES Arnold Road PACIFIC M ISSILE „ RANGE SANTA BARBARA Rincon oint Santa " C l a r a River TEST SITE Mugu Lagoon Point Mugu Laguna Point L O S A N G ELES SANTA CR NORTH MILES 57 almometer observations. One injection point was 50 ft from the deepest almometer (see Fig. 9). Description of the Area The Arnold Road Beach is situated on the southeast portion of the Oxnard plain about 7 miles from Oxnard and 60 miles from Los Angeles, California (see Fig. 8). The Oxnard plain is bordered on the north by the Ventura River and is also traversed by the Santa Clara River and Cal- leguas Creek. The plain is formed by the deposits of the latter two waterways in a structural basin. Ho rocks out crop in the plain. The alluvial fill is about 600 ft thick composed of Recent and Pleistocene sediments from gravel to clay with the former predominating (Kaplow, 1947, Page, 1963). The coastline bordering the Oxnard plain generally consists of a sandy beach varying in width from 50 to 300 ft and backed by a belt of dunes 50 to 2000 ft wide. From the Santa Clara River to Point Hueneme the coast trends N 25° tf. Southeast of Point Hueneme for 6 miles to Laguna Point the shore is straight, trending N 50° W. East of Laguna Point there is a small bight 3 miles wide at the back of which Mugu Lagoon is located. Offshore the sub marine contours are essentially parallel to the coast ex cept where they are interrupted by 2 submarine canyons and Figure 9 U. S. Army Corps of Engineers conducting RIST test at Point Mugu, California. 58 59 60 3 slope gullies. The two canyons Hueneme and Mugu come within 500 ft and 300 ft of the shoreline (Shepard and Hill, 1966). Atmospheric and Sea Conditions Winds The surface winds at Point Mugu are largely diurnal alternating between nighttime land breezes and daytime sea breezes. The sea breezes usually begin at 10:00 from the southwest at 5-10 knots and become more westerly 10-15 knots at 13i00. After the sun sets the wind dies down to a near calm and remains so until about 22:00 when the land breezes start usually less than 10 knots from the north or northeast. These remain throughout the night until sun rise when it becomes near calm. This regime is most noticeable in the spring and summer months but may be over shadowed in the winter by larger disturbances. The annual and monthly frequency distribution of surface wind speeds determined from more than 145,000 hour ly observations between 1946 and 1963 at the Mugu Air Sta tion are given in Figure 10. As can be seen, the pre dominant winds are from the west. These may set up local wind waves and chop which produce a southwest drifting littoral current. Of interest is Table 3 which lists not only the monthly averages but extremes as well. The Figure 10 Annual and monthly wind rose at Point Mugu (from DeVinolinl, 1967). 61 P o in t Muntt A nnual V/incl I*Op C (Oc la U r 1946 Thraufih ScplcroWr 1963)* 0 TO X 4 TO 10 II TO 1\ 71 TO JD 20 _!_ 62 3n J FRtQUI flCV 01' OCfUHHEi-Cr (PFRCIHT Of ALL VKAKHIA) JAXUAKY (1947-1*. 3) APRIL ( 1 N 7 - ! * J ) AUGUST m v e i i O E S ( W * -1962) DtCEUtiFJr 21 V Table 3* Monthly averages and extremes of surface winds at Point Mugu (October 1946 through September 1963) Most Frequently a { m Observed Direction Peak Gusts w o Percent of Observations 'w j s i l o < u * h o > S Month Direction Mean Speed (Knots) Observations (Percent) Mean Speed All Directions (Ki Maximum Obser Speed (Knots) Direction of Maximum Speed Speed (Knots) Direction Observations • Greater than (Percent) Calm Wind from Nt NNE, NE • h 3 S. 4-t W T3 * C 3 •H W 3 3 January NE 14 19.0 8.4 45 ENE 61 ENE 5.5 6.4 48.3 15.9 February W 11 13.8 7.5 39 NE 51 SE 3.8 7.2 38.1 23.4 March W 12 18.5 7.7 45 SE 52 WSW 3.7 7.1 29.1 31.9 April W 11 24.2 7.4 38 W 57 W 2.8 6.9 22.0 38.8 May W 11 25.9 7.1 36 W 49 tf 1.9 8.8 14.9 44.6 June W 9 23.4 6.4 30 SE 42 NE 0.2 10.5 12.7 42.6 July W 9 24.1 6.2 26 SE 33 SE 0.1 9.2 15.0 41.0 August W 9 22.5 5.7 36 SE 52 SE 0.1 11.3 18.5 37.2 September W 9 20.7 5.5 30 NE 42 NE 0.2 12.7 20.7 33.4 October W 9 15.3 5.9 36 W 53 W 1.0 9.9 32.0 26.8 November NE 13 15.7 7.8 50 NE 78 NE 5.1 6.6 43.3 18.1 December NE 14 20.2 8.5 50 W 70 ESE 6.5 5.8 48.7 14.3 Year W 10 18.2 7.0 50 NE/W 78 NE 2.6 8.5 28.5 30.8 Note: Maximum speed is the highest observed 1-rainute wind speed; the peak gust is the highest observed 5? wind gust. 64 strong north and east "Sant1 annas" are dominant in the late fall and winter. These gusts can deflate a beach as wit nessed in 19^8 by Inman (1950) when 2 cm of sand was re moved in a day and on October 4, 1971 when 3 cm were eroded. Tides A malfunction of the tide gauging station on the Experimental Groin obligated the use of the one at Rincon Island, 12 miles west of the site. The tides are mixed but dominantly semidiurnal (see Pig. 16). Since the autumnal equinox had ;}ust passed, the asymmetry is the least possible. During the days of the test the maximum tidal range was 7.4 ft on October 4 two days after the full moon. The minimum range was 1.1 ft on September 29. The mean range for the ten days was 4.6 ft. This compares to an annual mean range of 3.6 ft and an extreme range of 9*2 ft with a mean tide level of 2.7 ft (DeViolini, 1970). Sea State Every two hours measurements of wave period, angle of wave approach, breaker height and type were recorded. These are supplemented by the U. S. Navy observations of the same measurements plus direction and speed of long shore currents and by the U. S. Army Corps of Engineers deep-water wave-period and height records. The data is 65 presented in Figure 11. The breaker height averaged 2-1/4 ft and ranged from 1.5 to 3*5 ft. Each reading to the nearest 1/2 ft is an average of measurements on 20 con secutive waves. .These measurements are consistently lower than those of the Navy. Those were obtained from the Experimental Groin where the beach slope is much steeper. The breaker height fluctuated roughly like the tidal cycle. At high tide the breakers tend to be high due again to the increase in slope. The percentage of the breakers that plunge, never more than 90 percent and usually only 20-30 percent, are also in unison with the tide level but not nearly as spectacularly as their height. The angle of incidence of the breakers show that the waves came from both east and west in about equal proportions. Yet this seems to have little effect on the longshore currents. The longshore drift is predominantly to the east ranging from 0 to 0.7 knots. Only once was there a westward cur rent of 0.2 knots during the time of the test. Waves and Swell From the diagram (Fig. 12) it can be seen that the Mugu area is sheltered from many directions of wave ap proach. Only three unrestricted avenues are open; one through the passage between San Clemente and San Nicolas Islands; one through the Santa Cruz basin between San Nicolas Island and Santa Cruz and Anacapa Islands, and the Figure 11 Sea state at Point Mugu September 29 to Octo ber 8, 1971: Breaker height, breaker period percentage of plunging breakers, angle of wave approach, longshore currents. Observations taken every two hours. o Observations taken by the U. S. Navy from the Experimental Groin. a Observations taken from the records of the C.E.R.C. deep-water wave gauge. A 66 ° i.s. u rn A C . E . V . C . ' r ■ □ eo M o • • ■ OfifiQCQl •© O a P©0 4 O 0 4 V o ooo eo e o o o iA o o e oo o O - s 0 0 D 0 4 0 4 A A* eo a o oo oe e I I E A K E I I E I C I T a oeoo 040 • o - J ft oe o 00 o o o ooo oee o a oeoo oo ooooo oo eo oe - rfe “ 0 ^0 0 O O O P 4 - 1 A A A * * • * * a OO - e o “ 0 0 ® 0 0 0 - - £ U • m , a B - o**oo«M*t ”• • * • • • •a o*S *09 °r » O O OD. ooooewo o-“ o o oo- -O_ IIC » , o , ••o. o* : • f l o * - 10 WAVE P E R I O D □ oo'oo* % o " □ 0 • „ n- O p p e o „’o „ "o 0 0 08 ° e 0 □ _ q e o a j. n o e o e ooo #o oooo o ® 0 0 ° ( ,° o o 0 o°° 8oo ° "a o* . * °- ° 0 -0 . oo 0.0 0 1 0 1 »- 7. P E R C E H T « C E OF P L U N C I M C B R E A K E R S •8o • * *0*- O ■ 8° 0° - 3 0 ^ EAST ° 0 0 ooo ® e o _ o o eo - , *□«* 0- WIST o - J | INGLE OF RUE APPIQICI t t 2 ) S E P T J O * t LONGSHORE CURRENTS i l l ' , i n t o 3 I i qct - . 5 CIST I k i WEST o\ - J Figure 12 Diagrammatic Illustration of waves approach ing Point Mugu (after Inman, 1950). 68 69 5 < * V v v . S : 3; 9 3 If t S&3/ t *"Tisr 70 last through the Santa Barbara Channel for a total of only 74 degrees of azimuth (Inman, 1950). Because of the alignment of the shore between Point Conception and Point Hueneme, the area to the east is pro tected from all swells between north and N 72° W. The is lands give protection from west to S 68° W. Therefore, only 18° of arc is open to the westerly swell. These must then refract to the northeast over the shelf and diverge considerably before reaching the shore, thereby losing much of their energy. Two deep water wave stations (U. S, Army Corps of Engineers, 1962), one in the Santa Barbara Basin north of Santa Rosa Island (34.2°K, 120.0°W) and one in the Santa Cruz Basin north of San Kicolas Island (33.5°W, 119.5°W), show that during the year 75 percent of the swell comes from the west and ranges from 1 to 19 ft in height with a period of 6-18+ seconds but is predominantly (43 percent) 3 ft or less in height. Thirty percent of the time the swell is between 3 and 5 ft. The remaining 45 percent the waves are higher and from other quadrants (see Pig. 13)* Swell greater than 10 ft occur approximately 150 hrs a year. Waves higher than 17 ft are rare, being encountered only 2 hours a year* NOAA l/2 degree quadrangles (Pleet Weather Facility, 1971) show that only during the late winter and early spring is the swell higher than 2 ft more than 50 percent of the time. Figure 13 Swell and sea height and period in the Santa Barbara Basin (34.2°N, 120.0°W). After U. S. Army Corps of Engineers, Los Angeles District (1962). 71 P E R I O D H E I G H T S W E i L S E A 4 4 % 18 14 10 16 12 sec 15 9 * » i * » * __|__ ■ ■ * 0 20 40 60 80 100 % F R E Q U E N C Y O F O C C U R R E N C E The local wind waves are limited because of the short fetch. Only 70 hours a year is the sea higher than 10 ft. The beaches are open to local fronts for 135 degrees from 113-248°. At the deep water wave station the sea is predominantly from the west to northwest (47 per cent) with a 4-8 sec period. Especially in the winter do waves come from other quadrants (SIO, 1947), with the southeast predominating (6 percent). Almost half the time (44 percent) the local wind waves are less than a foot high. Littoral Processes Many studies (Handin, 1951; Trash, 1952; U. S. Corps of Engineers, 1952; Savage, 1957) show that the move ment of littoral drift is predominantly from west to east with reversals being quite rare. The primary source of the sediment is the Santa Clara River which prior to 19^8 deposited 1.4 x 10 yds- ' annually. After the construction of the Santa Felicia Reservoir and other dams, this amount has been reduced by about 50 percent (Watts, 1965). The detritus is brought down in quantities only during storms and deposited in a delta. Witness the 1938 and 1969 sub aerial delta extending 0.3 and 0.4 miles from the coast (aerial photos in Los Angeles District Office, U. S. Army Corps of Engineers). This delta then acts as a stockpile for the littoral nourishment in the following years. 74 The history from I856 to 1938 was one of accretion up to 400' at the mouth of the Santa Clara River tapering to 100' at Point Hueneme. Downcoast of Point Hueneme the shore was remarkably stable. The shoreline had almost the same position after 80 years (U.S.G.S. Hydrographic Sheet #554; U. S. Army Corps of Engineers, Los Angeles District Sheets D03348-4450). The Port Hueneme Harbor was constructed in 1938- 1940. The building of the jetties for the port blocked the downcoast movement of sand. About two-thirds of the total accumulated north of the jetty was diverted and lost into Hueneme Canyon (Savage, 1957)* The loss of a steady sand supply caused widespread erosion from the Harbor southward. In places the coastline eroded over 600 ft in f Z 10 years. Prom the Harbor to Laguna Point 2.5 x 10° yds^ were eroded between the survey line and the -24* contour (see Appendix II). To remedy this loss, the Army Corps of Engineers started hydraulic dredging in 1953-1954 taking 2.0 x 10^ yds^ from the Silver Strand accretion area to downcoast feeder beaches. Just eaBt of the harbor 1.3 x 10^ yds^ were emplaced and 0.7 x 10^ yds^ near Arnold Road (Savage, 1957). In February 1959 construction was started on the Channel Island Harbor two miles northeast of Port Hueneme. g This was completed in June 1961. In the process 6.2 x 10 yds^ were dredged and deposited just downcoast from Port Hueneme. Every two years "between 1.6 and 3.5 x 10^ yds-* is dredged from the sand traps west of the Channel Island Harbor bypassing Port Hueneme and deposited just east of it (June 1963, 2,0 x 10^; April 1965, 3.5 x 10^; January 1968, 1.7 x 106; September 1969, 2.7 x 106; September 1971, 2.4 x 10^; Dos Angeles Office, U. S. Army Corps of Engineers, 1972; and Allen Williams, pers. comm.). Even though the nourishment program is in operation, about 0.12 x 10^ yds^ are lost yearly to the -24' contour. This increases to 2.7 x 10^ yds^ if depths to the 30 ft contour are considered. The decrement Is most pronounced In the area where the sand Is deposited. Note the 200' diminlshment of the shoreline at station 10E In just 8 months (July 1970-March 1971) as shown in Appendix II. Sediment Distribution Sand samples were collected every two hours. At those times two 1-cm diameter tubes 5 cm long were scraped along the top of the sand in the middle of the swash zone. It was hoped that in this manner only the most recent sedimentation unit (Otto, 1938) was sampled. The samples are biased toward the smaller sizes for the opening of the vials precluded a representative sampling of the pebbles, cobbles, shell debris and tar globules. Tet they ac curately portray the sand population in the swash zone as that zone migrates across the beach face. The samples were 76 taken from 100-375 ft seaward of the U. S. Army Oorps of Engineers 1966 baseline. Upon return to the laboratory the sand samples were wet-sieved through a 0.62 mm sieve, dried and dropped in an automatically recording settling tube which records the hydraulic equivalence (Felix, 1969; Cook, 1969). The mean of the sediment is 0.160 mm with a mean standard deviation of 0.032 mm. Figure 14 presents the mean diameter of the samples and their distance from the baseline. This diagram clearly portrays the well-known (Beach Erosion Board, 1933; Bascom, 1951) relationship between the beach slope and mean sediment size. A quadratic least squares curve was fitted to the mean diameter of the samples utilizing the polynomial regression routine BMD05R of Dixon (1967). This program computes a regression equation of the form: Y =<£+P]_x = ^ 2x2 + * • • + e The equation which best fit the data is: Mean diameter (mm) = O.296 - 1.17 x 10-^ distance from the baseline (ft) + 2.0 x 10"^ (distance . 2 from baseline; An analysis of variance comparing the mean square devia tion about regression with that due to regression shows that both the linear and quadratic terms are significant at 95 percent. The standard error of the estimated re gression coefficients is for ^ 1.6 x 10 ^ and for j ®2 3.7 Figure 14 Mean sediment size In the middle swash zone on the beach and shore face at Arnold Hoad Beach, Point Mugu, California. 77 mm .200- X V .160- XX 120 - 360 320 280 120 160 200 240 feet from base Iine - 3 00 79 x 10-7. What the graph does not show Is portrayed in Figure 15* Here the mean sand diameter of the samples have been classified according to their relationship with the tide. Only those samples taken outside the period of slack water are shown. From this it appears that the top layer of sand in the swash zone is coarser on the ebbing tide than on the flooding tide. To test this hypothesis a poly nomial regression equation was computed for each data set. Ebb tide, mean diameter = 0.504 - 1.13 x 10“^ distance + 1.9 x 10"^ distance2 std. error^ = 2.1 x 10"^ ?2 = 4.7 x 10"7. -3 Flood tide, mean diameter = 0.293 - 1.25 x 10 ™ 6 2 /O distance + 2.4 x 10 distance std. error = 3.5 x lo"5 4 = 8.5 x 10“7. The estimated coefficients were then Jointly tested for 2 1 2 1 equality. Hypothesis ^ and p2 =(J2‘ can be tested by computing a confidence interval (Affifi and 2 2 Azen, 1972)^ t standard error $ (2 F1_A(degrees of l/2 freedom due to regression and about regression)) . H 1 is rejected if (3, is not within this confidence interval. Here at 95 percent the confidence interval for P-. - 1.13 x 2 lo“5 t 0.05 X 10"5 and for ? 2 - 1.91 x lo“6 t 0.01 x 10-6. Therefore, HQ is rejected and it can be assumed that the sand in the middle swash zone is indeed coarser during the Figure 15 Mean sediment size in the middle swash zone on the beach and shore face at Arnold Road Beach, Point Mugu, separated into dif ferences by tidal phase. 80 .2 40 mm .200 .160 .120 o fIo o d tide * ebb tide 0 0 0 T T 120 T 160 200 240 280 feet from base line 320 X 3 60 C D H 82 falling tide. Furthermore, a Mann-Whltney U test (Mann and Whit ney, 1947) was applied. This distribution-free statisti cal test determines whether two independent groups have been drawn from the same population. Independence within each group Is not ascribed but independence between groups is. The test is applied by ranking both groups (see Appendix III) in increasing size and computing the statistic U. U = nin2 + n2(n2+l) " ^2 is the sum of 2 the ranks of the second group. When the sample Is large, the sampling distribution of U rapidly approaches a normal distribution so that Z = U -Au = U - B]Ln2 2 (nx) (n2) (n^i^-1) 12 In the case at hand Z = 3*1 which has a probability of 0.001. If the foreshore is divided into 3 sections, 100- 150 ft or roughly the steep upper foreshore, 160-220 ft or lower foreshore to MLW and 220-375 ft or MLW-M1LW, the probability of the ebb tide deposits being coarser than the flood tide drops from 99 percent to 95 percent to 55 percent, respectively. The measure of asymmetry of the sediment distribu tion In the swash zone also show fluctuations that parallel the tidal cycle. If the moment skewness measure is zero, 83: the distribution is symmetrical. If there are relatively more coarse diameter sediments, the skewness is negative. Conversely, the skewness is positive for distributions with relatively more small sizes (Inman, 1952). Figure 16 shows the change of skewness with the tidal cycle. In all but three of the twenty tidal cycles the skewness becomes negative with the ebbing tide. The three exceptions occur where the tidal inequality is small (September 30, 2 ft; October 1, 3.3 ft; October 7, 1 ft). What causes this change within the middle swash zone of coarser grained sand with negative skewness at ebb tide and finer grained sizes with positive skewness at flood tide? If in the beginning a symmetrical distribu- tion of sand is present throughout the beach and shore face, the Beach Erosion Board (1936), Saville (1950) and Johnson (1953) have shown that the distribution of coarser grains higher up on the beach is due to the greater steep ness of the waves during storms. So that the actual dis tribution of sand sizes across a beach is a lag deposit. The size and skewness changes cannot totally be due to a lag deposit for they change with each tidal cycle. As the swash rushes up the beach, its velocity decreases gradually. The coarser grains brought in settle out be fore the swash advances to its fullest extent. At low tide when the swash has a long traverse the finer grains are held in suspension longer due to the higher swash Figure 16 Tidal curves at Rincon Point, California and fluctuations in the skewness of the sediment distribution of the middle swash zone at Arnold Road Beach with the tide from September 28 to October 8, 1971. 84 7 6 5 4 3 2 1 0 1 7 6 5 4 3 2 1 0 1 7 6 5 4 3 2 1 0 1 7 6 5 4 3 2 1 0 1 +.-.206 +%289 / ^ +/2?4\ + .184 _ +^073 +•*205 / • A 148 * . i + ■ ' \ • i H^.303 * • h -7^76 2 4 6 8 10 12 14 16 18 20 22 Q 2 4 10 12 14 16 18 20 22 +,280 \ + .2 7 2 + 7L96 A .097 { + \ 2 7 2 / . V 128 -t/*173 +Z091 Ab - \0 9 5 / 9 / 2 8 - 1 0 /1 - 1 0 / 2 " 1 0 / 5 10/6 - 10/8 86 velocities (Dolan and Perm, 1966) and settle out as a "blanket deposit over the entire inner zone when the swash velocity decreases to zero. Because of the gentle in shore slope and lack of infiltration, the swash period is considerably longer than the wave period (Emery and Gale, 1951)• Thus the large backwash after it has picked up momentum on its return to the sea picks up the fine grained sediment and transports it all the way back to the surf zone. This winnowing action that moves predominantly finer-grained sand downslope is aided by elutriation due to the escape of ground water (Emery and Poster, 1948) and leaves a residue of coarser material. Seaward of the middle swash zone where the trailing edge of the backwash deposits some of the finer sediment with the coarser residue, the sediment distribution is bimodal and skewed to the finer side (Duncan, 1954; Schiffman, 1965). As the tide advances above the ground water level onto the steeper part of the beach, the swash zone becomes narrower. The swash period is shorter, approaching that of the incoming surge. The swash velocity decreases rapidly due to the Increase in slope and infiltration. As will be shown later little sediment is carried across the surf zone, therefore the material brought to the swash zone can only come from what the final breaker has picked up from the foreshore which is relatively fine-grained. Thus the sand deposited is finer-grained than what is al 87 ready there. Furthermore, some of the coarser sand is removed by flotation to the furthest reaches of the swash to form a swash mark (Johnson, 1919; Evans, 1938b). Emery (194-5) noted that a thin wedge of water moving in front of the foam carries no sediment in traction and little in suspen sion but is capable of picking up dry grains, floating them further upslope and depositing them when the swash water sinks into the beach. McKelvey (19^1) in an excellent discussion of surface tension and wettability suggests that size and shape and especially dryness are important in determining the movement by flotation. Evans (1938a) found floating sand to be coarser than the sand from which it was derived. Profile Development The changes in beach profile during the period September 29 to October 7 are shown in Figure 17* Profile measurements were made during low tide and carried from the U. S. Army Corps of Engineers 1966 baseline (elevation at this spot 9.79' above MLLff) to the breaker zone. The method employed (Emery, 1961) is based on the measured difference in elevation between two 5' rods marked at 0.11 intervals placed 5' apart. The observer uses the horizon as a reference to obtain the line of sight difference in elevation between the 2 rods. Precision to 0.011 in the 5' Figure 17 Profiles of the beach at Point Mugu from the U. S. Army Corps of Engineers baseline to the breaker zone. 88 ELEVATION (FEET) 10 8 — 6 — -2 SEPT. 2 9 , OCT. 1 . 1971 OCT. 2, 1971 OCT. 3, 1971 OCT. 4, 1971 OCT. 5, 1971 OCT. 6, 1971 OCT. 7, 1971 DEC. 1 . 1971 JAN. 6, 1972 1971 2 — 0 — (MLLW) \ I I - I I | I II I 1 -I I I I | 1 I I I | M I - I | I 1 I I | I I I l -|-H I I | I M I - j — I - |\| 1 | 50 100 150 200 250 300 350 DISTANCE FROM BASE (FEET) 400 450 500 C D VO 90; linear distance is routine except in the surf zone where breakers block the sight to the horizon and the waves make holding the rods straight and separated 5' difficult. Experience (Emery, 1961; Kolpack, 1971) has shown that the precision of this method is comparable to that of a plane table and alidade. The profiles show little change in the beach face and lower foreshore and very little on the backshore. The largest difference between the September 29 and October 7 readings is 1.55* located at 150' from the baseline. This was the position of the berm before the spring tides. As these tides came the berm was progressively pushed back and increased in height making the scarp steeper. At the location of the other almometers the maximum elevation difference in the 8 days was 0.65*» 0.65', and 0.551 go ing from the shore seaward. As a comparison two other profiles are Included, one in December 1971 and one in January 1972. The December measurements show the development of a winter profile (Shepherd, 1950; Zeigler and Tuttle, 1961; Dolan, 1965) with a high narrow back shore and a high berm crest and deposition on the lower portion of the foreshore. The January profile shows the effect of removing the concrete caissons between the supports of the Experimental Groin which commenced on December 2, 1971. The removal of the impervious barrier allowed the stored sand to migrate beach drifting and longshore transport. ALMOMETER MEASUREMENTS OF SEDIMENT MOVEMENT General Statement The almometers were emplaced in a row 375* 270, and 190 ft from the "baseline 775 ft south of the Experimental Groin in water depths of approximately -0.5> 1 and 3 ft "below and above MLLW. Approximately is used advisedly for as Just stated the sand surface shifted a minimum of 0.5 ft during the experiment. The tubes containing the photo electric cells were placed so that the cells faced north west and therefore were never influenced directly by sun light. Measurements of the sediment movement were made every one-fifth second. This rate was chosen since the rapidity of sand movement was unknown and any aliasing had to be avoided. Two particular measurements are shown In Figure 18. These photos of the oscilloscope tube show a single time sweep of the photocells In the almometer on the upper beach face. Each dot represents a photoelectric cell. The horizontal scale is one volt per line. At this particular time 6 photocells or 12 cm were covered with sand. The next 5 cells show sediment moving past the almometer. Two cm above the bottom the surge contains 250 gm of sand per 92 figure 18 Measurements of sediment concentration changes with increasing height above the bottom on the upper beach face. The right hand picture is 5 seconds later. 93 94 95 liter of water. This concentration decreases to 90 gm/l 7 cm above the bottom. The movement of the last two blips show that the water 6 and 7 cm above the bottom has 3ust entrained the sand. The second photo shows the same almometer 5 seconds later. Now there is a measurable quantity of sand in the water 26 cm above the substrate. The bottom layer (#7 and #8) now contains 380 gms/l. This decreases irregularly to 130 gm/l 14 cm above the sand water interface. At a height of 15-18 cm above the bottom, the concentration is 100 gm/l. Then the concentration increases again to 180 gm/l 20 cm above the surface before decreasing again drastically. Computer Techniques This data and all the data were recorded on mag netic tape in analog form. This data then had to be digitized. Theoretically the whole curve representing the voltage of each of the 63 photoelectric cells could have been digitized but this would be extremely time-consuming and expensive. So from each curve four points were chosen. This number is limited by what could be digitized simul taneously per computer run. The values chosen are 10, 25, 60 and 90 percent of the maximum 4.9 volts obtainable at infinite darkness. From the calibration curve these volt ages equal 40, 75» 135 and 375 gm/l by weight or 15-2, 28.4, 51.2 and 142.1 parts per thousand by volume (weight x 0.379, assuming a sediment specific gravity of 2.7 and a sea water density of 1.025). It was found that voltages lower than 0.45 volts could not be accurately distinguish ed due to electronic noise in the recording apparatus. Also at these low voltages the calibration curve becomes asymptotic, thus small differences in volts give relatively large fluctuations in sand concentration. This is even more true when the output voltage readings go above 4.5 volts. There also the hysteresis effects can become pro nounced. There is one drawback in digitizing in this manner. Since the time sweep of the photocells in the almometer starts at the top, as soon as a photocell is reached which has an output of 0.49 volts its height is digitized. If there Is a decrease in the sediment concentration some where below this and then increases again, It is not counted. The same, of course, is true for the other points. Thus only the highest point reached by any of the chosen concentrations is measured and no provision is made for showing reversals in sediment concentration due to overtopping of the backwash and other means. These have been observed visually and will be discussed later. In the first computer run the 135 g/l value was digitized for the three almometers. In subsequent runs the three other concentrations were digitized a station.at a time. In order to condense the number of observations, a 97 smoothing technique hy a quadratic polynomial applied to 51 points using least squares was applied (see Appendix IV), By this means if is the data value at point i, then is the corresponding value on the curve L^p = £. + Pi6 + $2^ fitted by least squares. To do this (D. - ir 1 )2 has to be minimized. So let Y = ■ 1_j[I ) l K ip - £ - ^ ^t^2 - ^2^1^ 2* Tlien se' b " ti i e partial derivatives of Y with respect to <k} f t , , equal to o. If the ith point is centered at 0 and the data is taken at equal time intervals T, then t^ = IT. If = p + IT and = then D = 0c ; + ^1nT + £0n2T2 = jr ( rr + — — i=K np * 1 2 i=K No + Hi + H K0 “ N2 1^ Di T2 The computer-printed graphs of the smoothed data for the three almometers for three half-tidal cycles are shown in Figure 19-21. Limitations One noticeable feature of the graphs and the sum mary table to follow is the great fluctuation in sand level with time. Especially of note is the great change with the tide. Part of this, on the lower foreshore, Is due to coalescence of the scour pits around each pole of the almometer if the still water level is high and the velocity is fast enough. Like the renowned Heisenberg (1958, 1959) Figure 19 Data for three almometer smoothed by com puter for September 30, 1972 from 0200- 0800. 135 g/l value. 98 SEPT 3 0 3 Cm 1 Cm lOO 80 8 0 40 30 40 40 30 2 0 O 40 Cm 30 O I I | V' f A W - ll in A \ \ A u I J Jl.J'~ iJI -A A fed pn — t; e\_ y r A- VA S tA *_ ' T T I A, n. A_/ A. TIDE 0.5 3 . _ l _ i . - £ Jif- H, , J; A 1 / , I L . i*' Jy 1 L , i Li li 'Lv1 w VS.. t p c '■ i ' V \ '\{ ^AJ \M/ i/ lJ' * i J4 .Jl n I L A \ J r nvr ^ - —\ r V r-\ / ^ _ H. ■ > A/ ■ ^ 1.0 1 . 1 1 1 A A / A * JL 1 4 V \ I fto k , I A . u i- i\J 'V _ j A_ I VJ \. b_ /\ /L a JV A V f A- VJ A 1.8 K . J A l a 3a: lt\ P IK H r t 1 - e: A "i v J i : tcA P U t j r**> ! ! ! ! : s ! : : s ! S s ; ! ! ; s ! s ; ! ! : s ^ ! r - S ! : = ! : s s s n ! M m ; i n n ! ! H ! ; ; n s H 2.8 Hours /a t v I f An J A I t= ” 1 !L 3T H y V * V /V A JV r - V . j -* Ai -v IP 1 - . r \sJ J V \ — 1b*+ V »v \- /- v> a ) p f -AA A «kA v- J a : a/V ✓ i L. | -* CO Ft 3 i * I- 1 _ . . I: . 1 1 t a 1 , J l, 4 K . — j rur Ji, 1 J 1j j“" V J | i K [ y J V U r -I. a Li — i ! " j i ' A \ \ Iv ■"i I I , I l l ;"i h-i- ’ \ v L; v ■ > i r r I M lMi r*n : i a . ■M -L L r - -i _ l7’ .1 I, __ — a m . _ . ■ ^a ^a — i** _ a m a J _L ■ mm m m ^ — ■ m L m ^a a — _ m m m M aai ■a M -a ma ^ aa ^a a m — -JaaL| *ii_j -I 1.JL. ■ ™ j • fr l " T“ I■ i i- 1 —p - i] ' ' P TT 1 I - r —p1 " 1l i " pr| r —r- t l |1 1 T T " - p " p p^p- T - P ‘ PP m ma a ^rp p p T 1 _ | l i f t _ L- — J L TT ^ w C 7 ~ % i f l l V j : zj _ \ __ ^ _ --* \ r AJ A i > A- -MMi r a a “ ~ J ~ \r - f \ ^ / V - \ lJ J -L_,_ { \ k ' ^ - v I - ”1 — LI_J__L ii TT~if !ZIE Li iinLLLL m —i - a H am m n m ^ ■ a ^a a I I - -J _ ID p t i ■ St T-T T ~ T " ■" I V I1 r j T 1p | I' | 1 |■ I I *ip" r | 1 I"p" I""i » p p 1 I t *t 1 1 T" I- r - p 1 I 1 J T T ■ p r p T p p ^p-p p p 1T l ' 1 1 ; : i B 1 B B B ------- B 1 H K v j A J ' M i A l v h W M v J . i E : ii__ 4 i 2 I &\ 1ST Jl u I ft r ? w J*fll Vi v\' a ii j , jcslLi. VMY- M L m a V . StlLL Al . M44-- ,Uu& A^ai jt Figure 20 Data from three almometers smoothed by puter for September 30, 1972 from 1900 to October 1, 1972 at 0100 hours. 135 i value. com- hours ;/i 100 r = i ► - s - — f L < — " t < z i - * - =* > ► < ■~^s 5 r t _ 9 ■ n J > > 0* o'" OOOO h * & H S o U ( 0 0000 0000 «t«<l «« 0 M E E V V 0 1 H 20 lik b hi Q A ft . . . . 1 1 1 r \ . * A — L A J - A V V /“ /” V v/ V ~ s \ A/- w\/ V H /* \ I A j V A - A'v^’ ■ V! */^ , - A_ >Vi v v / us L jl j; 5 * 3 2 1 H 1 A 4 « 6 Hours 22 J 1 1 A f J i ^ J H . f t ) A l i J. 4 U A A ■ J ' ’ J ' 1/ * / J V v / y « N 5 I ' S " d p %j. A j- - _ - A m j J ^ ^ L> V ■ I k 1 J V I . Ft 23 J A. 2 * 1 £ f O i i ; s s s s s s s B » i i & 8 3 S s a s i s a a s s s i s s 8 79 7 * ^ ▼ ' O * to * 1 xt ■ J “ ■ ( ^ v a l lA C U\- Art, _____ id: L=: L * i—« s «_jf "AsJJ\ I \J^JvM/ulr Li _ - M •h N- v 3= M Figure 21 Data from three almometers smoothed by com puter for October 1, 1972 from 0200 to 0800 hours. 135 g/l value. 102 H » W - A A A 9 S 3 3 1 ' * AtlUk» aMU»» .IIUt» 0000 °0000 °0000 ! | | 3 “ i I 1 1 l A 1 1 | L- r f h \ j V 1 J V r- J l \ r J - VH iI L J J l k |w 1 I ' i 1 I I LJ *\j j \ ' \ \ r \ fV * - A - " y r - f f J L A a . _J WL . 5 p r = j 0 * 3 4 TT "T TT TT * m m m m m m TTTTTT \ . _ j j _ _ _ _ _ _ . JIJ ... 1 .. __i i; .1 i ll,M , 1 1 i I I I I i _i ‘Jl 11 i c v o T O o r T 4 M "J [55 JT, ".|L i-- .A __ v - i L nw. _A i I 1 / I J1 J A ( L 'V 0 1 S ■j VL /VA m \J J 1 * 2 Hours 5 ■ J T T T T '1 m ^ * "j] j _ ^ -A. -L.![! __ _ _ _ A . - A. ^ = !2= HM1 1 1 ,1 | * J i __ i _ J u _ A - v i A\- \ >mXXm n _ _JL _ "V \ i v w r- J * - v A ’J - A ? C f t - ___ P a / l 1 “ V _ " V _ M ^ " v \ ^ r * 7 5 F r A ^ ^J J" \A A /■ y l/> J ^ V - , / AA. * " T > / I m j * - — \ Ft 2 * 3 A u 3 t3 rv v A. 4 * 3 VOS y 1 1 --JI A 1 J n A*fil nli.f « r i, ,t\1 1 u "'0 L I l l i 1 > f t / \\k u\j- j , ' 'J1 1 i — r > S / 1 -- _ A\ rv _ r _ a - -A J "A*. A<u'iw u"V VLA i/iin>L N 1 ' ^ ^ 1 W J Jl 1 : ; A M . jJ 71/ H JvJV U " fV. 1 A 1 Ll£1 JJdilIL I •3 43 uncertainty principle, it is well nigh impossible to ac curately measure sand movement without introducing some distortion due to the measuring device. Figure 22 shows the small scour pits which were present when the beach face almometers were a foot below the still water level. The surface diameter of these pits was approximately equal to twice the diameter of the tube. An excellent presentation of scour induced by waves around obstacles has been made by Palmer (1970) from which the following has been drawn. Since water flows faster higher up in the water column, this sets up a pressure gradient along the vertical axis of the cylinder which induces an accelerated flow downward. Deflection of this fluid around the tube causes a "primary vortex" (Shen, Schneider and Karaki, 1966) which excavates the scour pit. Separation of stream lines around the obstacle increases the velocity to twice the unobstructed flow (Moore and Masch, 1962). This transports the sand lifted up by the primary vortex to the turbulent wake zone. At the rear of the obstacle the pressure gradients are the reverse of the front. The crowding of streamlines result in a turbulent wake with an upward velocity gradient. This sediment-laden plume rises to a height of approximately twice the cylinder's diameter (based on Palmer's photo graphs). This sediment can give artificially Induced re sults if the sand remains in suspension after the flow has Figure 22 Localized scour around the lower beachface almometer cylinder. 105 107 reversed. As the tide rose, only at the shoreface almometer did the scour pits rapidly become larger until the separate ones joined to form an oval depression 3 ft in the major axlB parallel to shore 2.5 ft in the minor axis and 9 inches deep. The rapid development of the larger pit seems to be independent of the wave height but dependent on the still water depth and the velocity. Wells and Sorenson (1971) give the direct dependency as h/gT and d/h. Many authors (Carstens, 1965* 1966; Roper, Schneider and Shen, 1967; and Palmer, 1970) have noted that the scour depth rapidly approaches a maximum and then stays constant. This is the case in the offshore zone. Therefore, although the sediment level indicated for the lower foreshore is spurious at high tide, the sediment fluctuations should be accurate. Only in the approximate l/2 hour during which the pits coalesced is the data unremunerative from the sedimentation viewpoint. In principle, however, especially with larger cylinders or greater proximity, an in situ method of synoptically measuring scour has been devised. In order to compensate for the scouring around the foreshore almometer a correction factor has been added equal to the measured depth of the depression. During the coalescing and refilling stages the linear factor 108 D was added (D = the measured depth of the scour pit, is the total time for the scour to develop or be re moved, T Is the time of measurement) to the recorded m depths. Once the depression has stabilized, just its depth has been added. During the last days of the test the two parts of that almometer were placed 3 ft apart. The coalescing of the scour pits came much later in the tidal cycle and averaged only 6 inches in depth. Future experience will indicate how far the cylinders have to be removed from each other to prevent the Joining of the pits. The data at this greater separation has not been included for no calibration was done for light scatter over that distance. Tidal Cycle Sand Movement It is known (Duncan, 1964; Otvos, 1965; Strahler, 1966; Giese, 1966; Schwartz, 1967) that three phases of beach changes can be recognized within each tidal cycle. First there is an initial phase of deposition as the swash zone of a rising tide first acts upon a section of the beach. This is followed by a period of scour as the tide rises and the section of beach is under the transition zone. Finally near high tide there is deposition again as the section is under the surf regime. On the ebbing tide the process is reversed. Table 4 lists the maximum heights of erosion and deposition and the time of their occurrence Table A. Summary of the maximum erosion and deposition and the time of their occurrence in relation to high tide across the surf zone Depo Occur Ero Occur Depo Occur Ero Occur Depo Occur Ero Occur Tide No. sition rence sion rence sition rence sion rence sition rence sion rence 1 none none +17 +7.80 none 1 2 + 9 -0.70 - 8 +1.00 + 8 +A.75 - 1 +5.00 3 A + 2 +0.38 - 2 +1.08 +11 +5.36 - 2 +5.76 1 +10 -7.6A -10 -1.00 II 2 + 2 -6.92 -22 -3.03 none 3 A + A -A.A7 - 3 -3.A7 + 3 -1.18 1 * * +12 -0.56 -10 +3.75 + 2 +5. AA none III 2 + 6 -3.55 - 8 -2.29 + 7 +1.A1 - 1 +2.1A + 1 +2.92 none 3 A + 1 -5.29 - A -1.22 + 2 -0.5A none + 3 +2.86 - 2 +3.32 1 none - 2 -3.12 + A -0.28 * * * IV 2 + 5 -5.82 - 5 -3.A2 + 1 -1.53 -18 +2. 5 A + 8 +3.26 - 2 +5.67 3 A + 2 -3.27 - 8 -1.93 + 1 +1.50 - 5 +3.58 + 5 A.67 - 1 +5.2A 1 * * * * * * V 2 +12 -5.78 -12 -3.53 + 8 -3.22 - A +0.52 +1A +6.33 none 3 + A -5.75 - 3 -1.67 + 3 +1.39 - 6 +2.03 + 6 +3.53 none A Table 4. Summary of the maximum erosion and deposition and the time of their occurrence in relation to high tide across the surf zone (Continued) Tide No. Depo sition Occur rence Ero sion Occur rence Depo sition Occur rence Ero sion Occur rence Depo sition Occur rence Ero sion Occur' rence 1 +17 -4.58 -15 -0.42 + 6 -0.44 - 6 +0.47 + 2 +1.42 - 4 +5.32 VI 2 + 2 -4.69 - 2 -0.50 + 4 -0.08 - 4 +1.17 none none 3 4 + 2 -4.50 - 8 -0.83 + 9 -0.25 - 6 +1.58 + 2 +5.42 - 5 +5.83 1 + 2 -5.17 * +14 -0.25 - 4 +3.25 +11 +6.42 none VII 2 none -13 -1.17 + 8 -0.08 - 8 +2.67 +14 +6.00 none 3 4 none - 3 -4.61 + 6 -1.25 - 3 +0.08 + 8 +1.83 none VIII 1 none -11 -4.08 +16 -1.67 -12 +1.84 + 9 +2.38 none 2 + 4 -6.41 - 1 -4.91 + 6 -2.58 -10 +3.75 +22 +5.25 - 2 +5.86 3 none - 5 -1.92 none - 1 +0.92 + 6 +3.67 - 2 +4.08 1 none -20 -4.16 + 2 +2.41 * +10 +6.10 none IX 2 + 2 -3.10 -13 -3.02 + 7 +1.83 - 9 +3.41 +19 +6.00 none 3 4 none - 4 -3.05 none none none none 1 + 1 -6.17 X 2 + 2 -4.82 - 2 -1.83 +12 +0.75 3 4 + 3 -3.75 - 2 -1.65 H O Table 4. Summary of the maximum erosion and deposition and the time of their occurrence in relation to high tide across the surf zone (Continued) Tide No. Depo sition Occur rence Ero sion Occur rence Depo sition Occur rence Ero sion Occur rence Depo sition Occur rence Ero sion Occur rence XI 1 2 none -10 -2.50 + 7 -0,75 - 7 +2.75 + 7 +3.75 - 2 +4.10 3 + 2 -3.25 - 5 -0.50 + 3 +0,50 - 2 +1.00 + 8 +2.17 - 2 +2.36 4 none - 3 -0.25 none none none none XII 1 2 + 2 -4.83 -11 -3.33 + 3 +0.67 -10 +1.25 + 8 +5.83 - 4 +6.26 3 hone - 5 -2.50 + 5 -0.83 -14 +4.50 +14 +5.50 - 4 +5.26 4 none -31 -0.05 none none none none XIII 1 2 + 2 -4.08 -10 -0.67 + 6 +1.33 - 6 +3,16 +14 +4.17 none 3 none - 3 -0,50 none none + 9 +3.08 - 4 +4.15 4 none none none none none none XIV 1 2 + 2 -3.92 none + 2 -0.75 -32 +2.75 +22 +4.70 none 3 none - 2 -3.25 + 2 -0.83 -26 +4.17 +30 +5.83 none 4 none none none none +11 +2.08 - 9 +3.50 XV 1 2 none -17 -0.91 + 6 +1.33 - 4 +1.92 +15 +4.67 none 3 + 2 -2.22 - 2 -0.94 +10 +0.67 -12 +1.83 none none 4 none none none none none none Table 4. Summary of the maximum erosion and deposition and the time of their occurrence in relation to high tide across the surf zone (Continued) Tide No. Depo sition Occur rence Ero sion Occur rence Depo sition Occur rence Ero sion Occur rence Depo sition Occur rence Ero sion Occur rence XVI 1 2 none -13 -3.00 none - 8 +1.17 + 8 +2.83 none 3 + 4 -4.75 - 2 -1.62 + 4 -0.11 - 8 +3.17 none - 2 +4.48 4 none - 3 -2.67 none - 7 +1.58 +11 +3.00 none XVII 1 2 + 2 -3.92 - 6 -0.08 + 6 +0.50 - 4 +1.25 + 4 +4.75 none 3 + 4 -1.83 none none none none none 4 + 1 -3.15 - 6 -1.50 none - 4 +3.00 none none XVIII 1 2 none - 4 -4.00 +17 +0.67 -11 +3.92 + 7 +5.92 none 3 + 2 -4.75 - 6 -2.91 + 6 +0.11 - 2 +4.58 + 4 +6.08 - 4 +6.32 4 -3, +4 -2.17 - 4 -1.00 + 2 +0.33 none none none XIX 1 2 + 7 -4.08 -19 -1.58 none - 5 +2.08 + 2 +4.12 - 2 +4.26 3 + 2 -4.58 - 2 -1.17 + 4 40.41 - 2 +2.64 none none 4 none none none - 4 +3.50 none none XX 1 2 none - 6 -3.88 +14 -1.05 3 - 1 - 2 -5.31 - 6 -1.39 none 4 none - 4 -3.33 + 3 -1.50 - 5 +5.00 Table 4. Summary of the maximum erosion and deposition and the time of their occurrence in relation to high tide across the surf zone (Continued) Tide No. Depo sition Occur rence Ero sion Occur rence Depo sition Occur rence Ero sion Occur rence Depo sition Occur rence Ero sion Occur rence Average: +0.4 1 +4.3 -5.89 -11.6 -2.55 +7.7 -0.20 -6.4 +2.33 + 7.7 +4.92 -1.3 +5.32 +0,1 2 +2.6 -4.76 - 9.1 -2.47 +6.1 -0.20 -9.1 +2.20 +10.2 +4.60 -0.6 +5.19 +0.5 3 +1.7 -4.13 - 4.1 -1.95 +3.5 0.00 -5.2 +2.40 + 6.2 +4.17 -1.6 +4.74 -5.2 4 +0.5 -2.66 - 5.1 -1.46 +0.5 -0.58 -2.0 +2.62 + 2.4 +2.54 -1.0 +3.50 * Sand height below the lowest photoelectric cell. Station Height: No. 1 - About 0.5 ft. mean lower low water. No. 2 - About 1.0 ft. mean lower low water. No. 3 - About 3.0 ft, mean lower low water. No. 4 - About 8.5 ft. mean lower low water. H ! H i 114 [ In relation to high tide for each of the four almometer stations. These elevations were obtained by taking the one minute constant maximum or minimum height of the 130 gm/l concentration. On the upper shoreface (#l) there is an initial period of deposition on 50 percent of the tides. This in creases to 70 percent along the beachface. The maximum thickness was 17 cm on the shoreface (#1), 12 cm on the lower beachface (#2), 4 cm on the upper beachface (#3) and berm (#4). The time of this deposition was very early in the tidal cycle so that only the first swashes could have deposited the sand. The average depths of erosion in the scour zone (Schwartz, 1967) under the transition also decreases shoreward from 11.6 to 4.1 cm occurring about 2 hours be fore high tide. The maximum observed was 31, 22 and 6 cm on the shore and beachface and 31 cm on the berm scarp. Only once was no erosion noticed before high tide ap proached. The time of maximum erosion varies considerably. On the shoreface it ranged from less than an hour to over four hours before high tide. On the beachface it ranged from 5 minutes to almost 5 hours. Deposition near the time of high tide slack water was progressively greater seawards. Going seaward the maximum deposition was 4, 10, 17 and 14 cm ranging in time from 3 hours before high tide to 2-1/2 hours after. Erosion on the ebbing tide was the greatest on the lower beachface. The most pronounced eroBion occurred on tide XIV with 32 and 26 cm eroded on the two beachface stations. At these same stations the maximum deposition of 22 and 30 cm occurred a couple of hours later. Figure 23 shows an hour of the smoothed data during this time. This diagram shows the maximum short term fluctuations in sand level observed during the test. On the lower beach face (#2) 9 cm was deposited in 3 minutes and 20 minutes later this was eroded again. Five consecutive surges (50 sec) deposited this total. On the upper beachface (#3) deposition was even greater--24 cm in 6 minutes. Here, also, surges arriving almost simultaneously (perhaps one bore overtaking the previous one) deposit 12 cm. Eleven surges pass without any apparent lasting effects, their passage being marked only by some sand being lofted above the bottom. The next surge deposits another 12 cm. None of this sand was in suspension for the highest fluc tuation of the 135 gm/l was only 3 cm above the substrate level. At this station also 20 minutes later almost all the sand which had been deposited had eroded again. Most of the erosion (10 cm) occurred with the passage of one surge. Upon its passage it eroded to its final depth within a second. A cloud of suspended sand hid the next three seconds. After this had settled the sand level re mained undisturbed for 20 seconds. Figure 23 Smoothed record of the maximum short term changes In bottom elevation in the surf zone of the 135 gm/l concentration across lower beachface (II), upper beachface (III), berm west (IV). No changes In vertical scale October 5, 1115* breaker height, 3-3*5 ft. T = 10.5-13 sec., 60-90 percent plunging. Approaching land at 5°-10° from the west. 116 60 40 m 30 20 0 60 40 m 30 20 0 60 40 m 30 20 0 ft j ! UU c o e h i , , ' ! f m jy E m n t o , h Mi ft u f f ' A A J W vn*UM UJ! A W XT' _ / | a. . J<A t tz w V * f i l l 50 100 SECONDS 1 1 7 us; Even on the term scarp (#4) 8 cm was deposited in 6 ; minutes. In contrast with the beachface, no determination can be made of the number of surges responsible for this deposition. The sand level gains a cm at a time at ir regular intervals without any accompanying suspended material. Here only after an hour did the sand wedge begin to be eroded. The sole patent difference on this ebbing tidal cycle was the fresh and strong offshore breeze. At 9:00 a.m. an hour before high tide the winds were blowing at a steady six knots. By 10:00 {high tide) they were blowing at 15 knots and gusting to 23. They stayed about constant until 11:30. Then in 10 minutes they dropped to 4 knots at which level they remained until 12:25. Then gradually they increased again, reaching their previous maximum be fore 3:00 and then slowly died out. The winds seem to be effective in dampening deposition at high tide and greatly expanding the usual erosion under the transition. Almost as soon as the winds died down for a short interval the maximum short term deposition took place. The maximum tidal cycle deposition took place after the winds had subsided. The average thickness of sediment deposition in the ebb tide swash zone was 7.7 cm on the shoreface. This increased to 10.2 cm on the lower beachface and decreased to 6.2 on the upper beachface and 2.4 cm on the berm scarp. 119: Going shoreward ebb tide deposition occurred in 100, 95* 70, 35 percent of the tides. The last changes in topography that occur before a section of beach is above the swash zone is erosion. Al though this occurs (going shoreward) in 17, 35, 59, and 11 percent of the tides, it is important to obtain an overall balance in deposition and erosion per tidal cycle. As can be seen, the average change per tidal cycle at Point Mugu during the days measured is half a centimeter or less except on the berm. Demise of a Berm Berms, both winter and summer, are a prominent feature on most unprotected beaches. To determine how spring tides effect a summer berm, an almometer was em- placed on the apex of the berm crest 8.5 ft (260 cm) above the MLLW. Eleven consecutive tides were monitored from October 3-8. These reached heights of 5*9 ft (180 cm), 5-7 ft (173 cm), 6.4 ft (195 cm), 5-2 ft (158 cm), 6.8 ft (207 cm), 5*0 ft (152 cm), 6.8 ft (207 cm), 4.4 ft (134 cm), 6.8 ft (207 cm), 4.0 ft (122 cm), and 6.2 ft (189 cm). The previous tides of 5-7 ft (174 cm), 5*1 ft (155 cm), 5.6 ft (171 cm) and 5.9 ft (180 cm) elevation steepened the slope of the upper beachface from 1:51, l!36, 1:20 to 1:12. On the last tide before the berm was overtopped the uppermost swash marks reached 8.2 ft (250 cm). There 120 at an elevation 10 cm "below the crest elevation, a micro- herm was deposited. This feature had progressively moved up the beachface with each succeeding tide. In tide XI when the still water height reached 5*0 ft (152 cm) three cm of sand was eroded in two steps 5 minutes apart. The swash uprush must have attained a height of at least 160 cm for the first erosion occurred after sand in suspension reached that elevation. Only one other wave was recorded which stirred up the sand 3 cm but the grains evidently settled back in place for no erosion ensued. The next swash to reach the station was 40 seconds later, lifted up the sand 6 cm and eroded 1 cm. Although the tide rose 21 cm higher, no more sediment movement is recorded. The highest swash reached 265 cm. Prom all evidence only 2 surges did all the erosion. Pre sumably most of the time any surge reaching the station infiltrated into the sand. The following day (tide XII) when the still water level was only 1.3 ft (39 cm) and 2.3 ft (70 cm), the sand level dropped 3 cm. There is no record of any swash reaching the station so it must be assumed that either there was an error in the recorded readings or, more likely, the sediment rearranged itB packing after the bouyancy effect of the previous high tide water Infiltra tion waned. As the water rose higher from 5-6.2 ft (152- 189 cm) 3 cm were eroded in an irregular manner. As can be seen (Fig. 24) frequently what was eroded was redeposited. There are 20 changes in elevation recorded, yet 49 dif ferent times was the sand of 135 gm/l density raised at least 2 cm above the bottom. On the other hand, not all changes in elevation occur after these sand uplifts. Three times, twice in erosion and once in deposition, the sand level was not disturbed before the event at least within the limits of measurements. During the next half hour as the tide rose from 6.2- 6.3 ft (189-192 cm) the sediment level dropped 28 cm. A more detailed review of the record shows that the descend ing staircase is not quite as smooth as pictured but that many waves deposited sand only to be eroded again by the next wave. The greatest amount deposited was 4 cm. The same is true for erosion. Fifty-three times the sand was lifted above the bottom, frequently followed by erosion. The erosion stopped before the tide crested. No net deposition or erosion occurred on the fol lowing two flooding tides (5*2 ft and 6.8 ft) (158cm and 207 cm). The later tide (XIV) was certainly high enough to reach the station as the highest swash marks left by this tide reached 271 cm. But as noted before a strong seaward wind was blowing at this time. As the tide crested and began to drop (6-5.6 ft, 183-171 cm), 11 cm were de posited. This appears to be the work of three successive waves. As the tide continued to ebb to 94 cm (3-1 ft) the Figure 24 Changes in the summer berm elevation with the advent of spring tides October 3 to 8, 1971* The curves were obtained by taking the lowest elevation of the 135 gm/l concentration that was constant for 30 seconds per 2 minute period. 122 2 5 9 H I G H T I D E W A T E R L E V E L CM ■V. 1 7 3 cm «■ 1 9 5 222 222 1 5 9 2 0 7 2 2 4 1 5 2 2 2 4 2 2 5 2 1 5 2 1 4 ' V W V ~ 2 0 7 1 3 4 2 0 7 122 1S9 I I I 1 0 1 HO UR S B E F O R E A N D A F T E R H I G H T I D E 123 124 recently deposited sand was almost completely eroded again but much more slowly and replete with reversals in trend. The next high tide (XV) was only 152 cm high. It did not influence the sand elevation although the sand level was only J4 cm above the still water level. Tide XVI was the same height as XIV. This time 10 cm were eroded before the tide peaked, one-third of it quite early (5-7 ft, 112 cm). As this tide ebbed (6.5-5.1 ft, 198-155 cm), 11 cm were deposited. Of this 8 cm were deposited in 8 minutes. The following tide (XVII) was only 4.4 ft (134 cm) high. Yet when 76 cm was attained a cm was deposited. Then four times this was eroded before the tide peaked. After the crest as the water dropped 3*3-2.8 ft (100-85 cm) another 4 cm were eroded. On the next higher high tide (XVIII) 4 cm were eroded, then as the water reached 5.1 ft (155 cm) 4 cm were redeposited. This same amount was eroded again and then deposited again after the high tide slack water. October 8 brought a high tide of 4 ft (122 cm) which ebbed to 3*5 ft (107 cm) before 4 cm were eroded. On the flooding tide of the next tide (XX) 4 cm were eroded, then 3 cm redeposited before the tide crested. As it fell 5 cm were eroded. As can be seen in the summary, Table 5, in the 10 tides monitored there was a net loss of 55 cm on the berm. Table 5. Summary of topographic changes in the destruction of a summer berm by spring tides* Tide Sand level at begin ning of tide Sand level of survey Flood tide water level and sand elevation changes Peak high tide water level Highest swash mark Ebb tide water level and sand elevation changes XI 259 259 152 - 3 173 265 XII 256 39 152-194 - 3 -31 195 268 XIII 222 226 158 XIV 222 207 271 183-171 +11 171- 94 - 9 XV Ilk 152 XVI Ilk 112 180-192 - 3 - 7 207 198-155 +11 XVII 1 225 76 113-128 + 1 - 2 - 4 134 100- 85 - 4 All values are in cm. H r o V J l Table 5. Summary of topographic changes in the destruction of a summer berm by spring tides (Continued) Tide Sand level at begin ning of tide Sand level of survey Flood tide water level and sand elevation changes Peak high tide water level Highest swash mark Ebb tide water level and sand elevation changes XVIII 216 215 106-128 - 4 155-179 + 4 180-207 - 4 207 277 207-182 . + 2 * XIX 214 122 107- 94 - 4 XX 210 207 100-164 - 4 167-174 + 3 189 76- 51 - 5 H ro o\ 1271 But more than half of this occurred in one tidal cycle. The first action of swashes reaching the berm on a rising tide is erosion. Only once in the 10 tides monitored was deposition first and then to the extent of only 1 cm. As the tide rises a sand wedge is deposited. This wedge is about 3-4 cm thick. If the tide rises more, this wedge is eroded as the area enters the scour zone. If this zone is not reached, the wedge remains during the high tide crest. In fact, in the tides measured elevation changes occur only twice during the slack tide. On the ebbing tide if the sand wedge was not eroded before, it is at that stage. If it was eroded before the higher high tides, a new sand wedge is deposited. Twice this prism was more than 10 cm thick. This deposit perdures until the advent of the next tide. SAND FOUNTAINS General Statement Since Aibulatov's (1958) excellent study, coastal engineers have been aware that suspensions of sediment occur in spurts under the influence of waves. These sudden upheavals of bottom sediment have been called sand fountains by Zenkovitch (1967, p. 121). As seen before and in Figures 25-27, these clouds of sediment above the bottom are short in duration. The three lighter concen trations usually mimic each other rather closely. The 375 gm/l concentration, at times, follows a much more sub dued path and shows reversals not experienced by the lighter concentrations. Approximately 50 percent of the time deposition occurred after one of these sand uplifts. Extent and Location of Sand Fountains To determine the extent, size and shape and loca tion of these fountains, the 135 gm/l concentration fluc tuations were analyzed in detail for 24 magnetic tapes (103.7 hrs). Table 6 shows that during the 9 tidal cycles studied, 1213 sand fountains occurred. The table shows that during the flood tide as the breaker zone traversed 128 Figure 25 Sand fountain on upper beackface September 30 22:40 Ebb Tide 2.7 ft Classification g Bhot . 130 Zl 01 I 8 9 I 11 I * T \ III 3 -0 -01 -0 2 -0 £ -Ot Figure 26 Sand fountain on upper beachface September 30 22:53 Ebb fide 2.1 ft. Classification 2 T AacC . Right: Sand fountain on lower beachface October 1 23:50 Ebb Tide 1,2 ft. Classification SAbc*. . 131 S E C O N D S - 40 c m - 30 - 20 - 10 - 0 132 Figure 27 Sand fountain on shore face October 2, flood tide 0.7 ft. Classification £)Ba£ . 133 -40 40- c m c m t j 0 0 10 20 30 S E C O N D S Table 6, Distribution of sand fountains across the surf zone nine tidal cycles Overall Total Tide level (ft)___________-1-5______-I_______0________1 Hours Rising tide 55.4 2.6 9.0 5.3 Falling tide 48.3 2.6 8.3 6.2 103.7 5.2 17.3 11.5 Sand fountains Rising tide 799 5 15 4 Falling tide 414 1 26 9 1213 6 41 13 Frequency (hrs) Rising tide .12 .52 .60 1.32 Falling tide .16 .32 .69 Length average (sec) Rising tide 9.2 13.8 13.7 5.8 Falling tide 11.9 15.0 14.8 14.1 10.2 14.0 14.4 12.9 Height average (cm) Rising tide 23.6 18.4 18.9 23.0 Falling tide 23.7 19.8 22.2 21.7 23.6 18.6 20.9 22.1 with changes in tidal elevation during 2 5.6 9.2 14.8 7 1 8 .80 3.9 4.0 3.9 17.5 17.0 17.4 3 6.7 4.3 11.0 7 __6 13 .96 1.07 5.7 3.5 4.7 29.4 19.7 20.4 4 5.2 5.4 10.6 25 _8 33 .35 .64 5.3 4.6 5.1 21.8 22.9 22.1 5 4.5 4.0 8.5 16 __2 18 .41 5.42 4.6 3.5 4.5 20.9 20.0 20.8 Total or Average 38.9 40.0 78.9 79 53 132 .61 .46 7.4 11.2 9.0 20.5 21.7 21.0 Table 6. Distribution of sand fountains across the surf zone with changes in tidal elevation during nine tidal cycles (Continued) Tide level (ft) Lower Beachface (#2) Total or Upper Beachface (#3) Total or 0 1 2 3 4 5 Average 2 3 4 5 Average 9.3 7.9 7.5 11.4 9.7 7.0 52.8 7.5 11.4 9.7 7.0 35.6 8.3 7.0 7.7 7.8 9.1 6.3 46.2 7.7 7.8 9.1 6.3 30.9 17.6 14.9 15.2 19.2 18.8 13.3 99.0 15.2 19.2 18.8 13.3 66.5 5 26 7 2 1 4 45 32 407 219 17 675 1 50 24 1 1 0 77 7 142 109 26 284 6 76 31 3 2 4 122 39 549 328 43 959 1.86 .30 1.07 5.70 1.75 .23 .03 .04 .41 .14 .32 1.10 .05 .08 .24 15.6 13.5 8.6 6.0 4.0 8.5 12.0 8.3 8.5 10.8 9.9 9.2 16.5 16.5 13.1 4.0 4.0 15.1 8.6 11.8 11.3 8.2 12.0 15.8 15.5 12.1 5.3 4.0 8.5 14.0 8.4 9.3 11.0 8.9 9.8 18.6 21.1 22.5 32.3 26.0 38.0 23.1 20.7 22.8 26.8 24.0 24.0 17.0 23.2 24.4 16.0 16.0 23.3 20.4 23.6 24.5 26.8 24.2 18.3 22.5 24.0 26.9 22.0 38.0 23.2 20.6 23.0 26.0 25.7 24.1 Hours Rising tide Falling tide Sand fountains Rising tide Falling tide Frequency (hrs) Rising tide Falling tide Length average (sec) Rising tide Falling tide Height average (cm) Rising tide Falling tide C J \ c the position of the almometer, the time that the bottom photoelectric cell was covered with sand decreases but in creases again as the almometer is seaward of the breaker zone. At no time, though, is the shoreface almometer com pletely above the sand more than 30 percent of the time. But even with the bottom cell uncovered, turbid clouds rising above the bottom are monitored and included in the tally. If the sand fountains had occurred with the same frequency as those recorded, 1246 would have taken place, an increase of only 2.7 percent. As can be seen, almost 80 percent of the explosions occur at the almometer on the upper foreshore. This is certainly contrary to expectation, especially In light of the fact that It was above the still water level 40 per cent of the time. Part of the explanation must lie in the effectiveness of flow In the swash and transition zones in suspending sediment. Over 87 percent of the sand fountains occur when the still water level is within a foot above or below the elevation of the almometer stations. Also Inman (1949) notes that sand of 0.18 mm diameter is the easiest to transport. Just shoreward of the 3rd station the sand Is of this diameter whereas seawards It Is finer. This, however, does not explain the 2.5 times greater number of sand uplifts occurring on the flood tide com pared to the ebb, which is not true for the other stations. Part of an explanation may lie In the fact that the 3rd 138. station on the flood tide Is above the still water level whereas on the ebb tide it is below it. On the ebb tide sand below the water table is somewhat indurated because of the surface tension imparted by the ground water* This water table lags one to three hours behind the tide (Emery and Foster, 1948; Fausak, 1970) in its descent down the beach to its low water level near the lower beach face station. This surface tension combined with a probable decrease in the roughness coefficient due to the water makes it more difficult for the sand to be suspended. The almometer on the lower foreshore registered the least number of the sand uplifts (10 percent) while it was below the still water level only 14 percent of the time (14.5 hrs). Near the almometer on the shoreface 10.8 per cent of the explosions occurred while it was under water all the time. This can only mean that in the breaker and lower surf zone the predominant means of sand transport is not by suspension but rather by bedload. Johnson (1952) reportB that in this area with relatively flat waves the major portion of sand is moved along the beach by bedload whereas when the steepness ratio exceeds 0.025 movement it is by a combination of bedload and suspension. During the test the waves were very flat (H0/L0 = 0.002). The breaker zone in general and the plunge point in particular is difficult to locate accurately. During these tests with the wave conditions prevailing the plunge 139; i point moved past the shoreface almometer when the ground water level was "between 3*0 and 4.0 ft and past the lower beachface station when the tide rose above 4.5 ft. When the tide waB at these levels only 4 percent of the sus pension clouds occurred. The approach of the breaker zone as the tide rises or falls is signaled by a decrease in the duration of the uplifts. The average time drops from about 14 seconds to 4 seconds. This dramatic decrease in the length of the fountains is true on the lower two stations but not on the upper beachface which was not In the breaker zone during the time in question. Certainly this decrease in time must be due to the increase in velocity near the breaker zone. Therefore, though few In number, the sand fountains occurring near the breaker zone may move considerable quantities of sand. The sand uplifts range in duration from only half a second to 53 seconds, averaging 10.2 seconds. On the ebb tide the fountains last somewhat longer than on the flood tide. This can be so since the sand in the swash zone is coarser on the ebb tide than on the flood tide and it is negatively skewed, therefore the material in suspension should be somewhat finer. The longest uplifts occur on the relatively flat shoreface and lower beachface during low tide. This may be due not only to the finer sand sizes prevalent there but also to the slower speed of the "backwash.. The tide level is relatively insignificant in effect ing the heights attained by the suspension clouds. The highest 135 gm/l turbid zone reached 100 cm above the bottom. This occurred on a rising tide in 3-5 ft of water under the breaker zone. Even the -40 gm/l concentration rose above the limits of measurements (112 cm) only four times. Table 6 discloses that the average height of the fountains is 23.6 cm on the rising tide and 23.7 on the falling tide. There does not seem to be any correlation between the height and the length of the sand fountains as is shown in Figure 28. The frequency of occurrence of the sand fountains was computed and also shown in Table 6. To obtain this number the time between successive suspension clouds after the first uplift per tide had occurred was averaged. At the upper beachface almometer the occurrence was the shortest, 1.7 and 2.6 minutes during the rising tide when the still water level was 3-5 ft. During the same tidal stages on the ebb tide the average time between them was 3.3 and 5.0 minutes, respectively. Plotting the actual times between occurrences (Fig. 29) show that for this almometer when the tide level was between 3 and 5 ft only two small peaks stand out amidst the scatter. These are 15 and 21 seconds. The first is undoubtedly the pre dominant wave period. The second may be due to the inter- Figure 28 Height versus duration of sand fountains on the shoreface and lower beachface and upper beachface with changes in tidal elevation. 141 STATION 6 0 5 0 IN T I D E H E I GH T ft 1 2 □ B • 1 - 0 B a 0* 1 0 B 1 * 2 A A 2 * 3 O • 3 - 4 0 0 4 - 5 © e s - e 60 5 0 c m cm 4 0 A A 4 0 B 30 3 0 b « A a © a A B a a a © a a h a a © a a 0 (90 <D0 00B BO B S Efl O 2 0 0 dfla QAeAO © G P a ® a a aa© o b _ b a h 0 00 h“b b BOQfiUOO □ b S b b b b i 9 B B 0 k 0 B j f t t A B BBB B^ b b a a a b w d 9 6 h a □ b a i 0 B B a B A B 0 3 B 0 A0 0 0 O O O BflA 0 B « 3 0 20 1.0 2,0 3 ,0 sec 4 , 0 111 2,0 ill 4 , 0 sec 5 , 0 H - P > ro F L O O D I N G T I D E E B B I N G T I D E Figure 29 Frequency of occurrence of sand fountains on the upper beachface. 14? GO 50 CD 40 30 20 I T I D E H E I G H T ft 2 - 3 + nombtf of p o in ts 1 1 3 4 S t 7 S » 1 0 4 • 5 a a a s a ■ ■ ■ a a 5 ■ 6 * 60 50 □ □□ o o □ □ 0 □ □ □ s o □ □ ca □ □ □ □ □ □ □ O S D o □ B O D D O □ 00 o o o a o c s a o o o o oo 03 O O OS a i QWTQ rv\ q o □ BOO □ □ O m m scoD O Q offi s o o c ® o - t o o s o O S 0 0 0 * 0 3 0 B CD OOO a® o s a o a o o o o o c © B ® V B 04Q 3Q & 00 aftrwnotTrBn O O C d 0 o o s s o q ssc b s ♦+ a s c n o m OO □COV9CO«SD9SOO 0 G D «9B Q © D 90000a □ OO OGOSOC><£& #TiA A ra o q zootfm w ro <b *€sd» o s o o OODd+0^«CS*€w*ltlQ>+& H a B 9 M S * « a T f t lS « 4 - A G O © OOfOCaQdOG 0 0 A * t 4 0 > B M I > OO O □ A □ o □ □ o BO OO □ 0 BO 0 o o □ A o a c a o o □ b o o a OOO o □ OPOO A S OO □ t o o ODD A O OOO A a o ♦ a ADO (SO □ □ OG AO O £09 O COO □ o d d c d c d rp /v r ? □ A A D CDDOCB^fiAO O n a aaiqw^ti r m m O A OO GOO A GO A A O A OSODCICOOCO 0 □ O □ <DOCGQ>a BOO O BA ■ w m p OG 0 □ g o a o a + o a a o a □ a s o+ O H o o o o o o 40 30 20 ill M. 3,0 4,0 1 . 0 ill 3,0 4,0 tec F L O O D I N G T I DE see E B B I N G T I D E 144 ference of wave trains of shorter period or more likely the somewhat longer period of the backwash. Shape of the Suspension Clouds The sand fountains were classified according to their shape. If the 135 gm/l suspensate cloud rose and dropped immediately as it moved past the almometer, it was designated as A; if, however, the cloud stayed at about the same height for over 5 seconds, it was called B. A further subclassification delineated the types of peaks: (a) the peak is symmetrical on both sides, the time it took for the cloud to rise is equal to its fall; (b) if more time is required for the sand to reach its highest point; (c) if more time is needed for its fall. If the sand was stirred up, then dropped but not to the original level of the substrate and then rose again, it is des cribed as (f) if the first peak is higher, (g) if the second peak is higher, (h) If both are of equal height. If the 135 gm/l suspensate level was at the same height (b) for a period of time it was sometimes stirred up more for a short period of time, thus (k) is used If the cloud stayed at a given height, rose higher, was at this new level for over 2 seconds and then dropped to the original level before disappearing; (l) designates a peaked super numerary In the center of the plateau; (m) if the peak is last and (n) If it is first. The first four letters of 146 the Greek alphabet show the differences In the rise and fall of the cloud above the bottom; cC describes a rise or fall from the highest point of the peak in a smooth way usually in not more than 3 seconds; (3 is used if the as cent or descent is a series of small steps taking up to 20 seconds; If describes a cloud that has a lower plateau on one or both sides of the top; £ > is a small peak which occurs before or after the main one. A typical example of a sand fountain description is and looks like Figure 30. Figures 25-27 show other types. Table 7 lists the occurrences of the different types. As can be seen the great majority of sand fountains near the shoreface and upper beachface almometers are peaked. When enough measurements exist to make a meaning ful comparison, the majority of sand fountains on the lower beachface are flat. The smallest percentage of peaked fountains occur when the tidal stage is a little higher than the almometer station. Taken as a whole the suspension clouds rise abruptly from the bottom on the flooding tide and die out more gradually. Whereas on the ebbing tide they rise with less suddenness and wane even more slowly. The higher the tide the shorter the rise time, but also based on the 3rd sta tion there are more small plateaus before the major uplift commences. As the tide increases the clouds also die out Figure 30 Top: Bottom: Frequency of occurrence of sand fountains on the upper beach face. Sand fountain, September 28, 1972, 2151 FCT, ebb tide 1.4 ft above datum, lower beach face, breaker height, 2.5 ft, period = 13 sec, waves approaching 100 from the east with 10 percent plunging breakers. 147 148 f r e 1 e n c y 2 l 100 40 6 0 SO 2 s e c o n d s cm 20- 10 0- . fV ; U U 1 1 J ~ A S' a p i i p j \ * i jj ms . . J . S J— > r "niH7 w . I 4 A T v iAl...- I 6 Y SECONDS Table 7« Classification and occurrence of sand fountain types Sand Fountain Shape Tide level Shore Face (#1) Total -1 0 1 2 3 4 5 Rising tide A 3 10 3 7 6 15 15 59 B 2 5 1 1 10 1 20 5 15 4 7 7 25 16 79 dC 3 4 4 7 5 17 14 54 2 8 1 5 2 18 y 1 1 2 4 h 2 1 3 *L 2 3 4 7 4 21 14 55 9 3 10 1 4 2 20 y 2 1 3 h 1 1 a 3 10 3 6 7 16 14 59 b 2 2 c 2 1 1 2 6 f 2 1 2 5 S 3 3 h k 1 1 1 m 1 1 n 1 1 2 Falling tide A 1 17 8 1 4 2 2 35 B 9 1 2 6 18 I 26 9 I 6 8 I 53 cC 1 6 4 1 6 4 2 24 9 17 3 20 % 2 1 2 5 & 1 1 2 4 1 8 7 1 5 4 2 28 (3 18 1 1 2 22 * 1 1 2 % 1 1 a 1 14 4 4 3 1 27 b 3 1 4 c 1 1 2 f 1 1 g 2 2 1 5 h 5 2 7 k 1 2 1 3 m 3 3 n 1 1 Table 7» Classification and occurrence of sand fountain types (Continued) 15G Sand Fountain Shape Tide level Lower Beach Face (#2) Total 0 1 2 3 4 5 Rising tide A 2 8 2 2 1 3 18 B 3 18 5 1 27 5 26 7 2 X 4 45 eC 2 8 5 2 1 3 21 P 1 12 1 14 T S 1 2 1 4 & 1 4 1 6 <£ 2 12 5 2 2 23 P 3 11 2 1 17 * 2 1 1 4 & 1 1 a 3 15 4 . 2 1 3 28 b 2 2 4 c 2 2 f 1 1 2 g h 2 2 4 k 1 1 1 m 3 1 4 n Falling tide A 1 17 12 1 1 32 B 33 12 45 I 50 24 I T 77 dC 1 25 7 1 l 35 p 20 9 29 3 4 7 % 2 4 6 1 14 17 1 l 34 P 24 3 27 * 9 2 11 6 3 2 5 a 1 22 10 1 34 b 8 1 1 10 c 3 3 f 1 1 2 g 3 2 5 h 8 4 12 k 1 2 3 1 1 1 m 2 4 6 n 1 1 Table 7, Classification and occurrence of sand fountain types (Continued) 151 Sand Fountain Shape Upper Beach Face (#3) Tide level 2 3 4 5 Tota] A 20 267 111 13 411 B 12 140 108 4 264 32 407 219 17 675 c f c 15 226 114 8 363 12 101 62 5 180 V 2 33 28 4 67 & 3 47 15 65 t£ L 12 126 73 5 216 * 16 199 91 6 312 Tf 4 41 32 3 80 b 41 23 3 67 a 19 216 106 11 352 b 3 17 9 1 30 c 5 70 20 95 f 3 11 8 1 23 g 11 10 1 22 h 1 19 18 1 39 k 22 12 34 1 2 8 10 m 7 12 1 20 n 1 32 16 1 50 e A 6 82 65 18 171 B 1 60 44 8 113 7 142 109 36 284 2 53 52 17 124 3 51 34 4 92 K 1 17 13 5 36 & 1 21 10 32 £ 2 33 29 6 70 4 92 65 11 172 X 4 7 3 14 h 1 13 8 6 28 a 4 76 58 16 154 b 2 12 9 2 25 c 1 11 10 1 23 f 7 8 15 8 5 6 3 14 h 7 7 2 16 k 10 1 11 1 3 3 ra 3 3 2 8 n 8 7 15 152 more slowly with secondary peaks more common. Table 7 shows that more than half of the sand fountains are symmetrical. Almost all the time that the uplifts lasted less than a second they were also symmetri cal and rose and fell without any prior or posterior minor uplifts. On the flooding tide about half the number of peaks rose more slowly than on the ebbing tide. The re verse holds for the slower fall of the explosions. The other types of fluctuations are about equal for both tidal phases. Quantity of Sand Moved by Suspension The amount of sand moved by these sand fountains is considerable. To determine the quantity of sand involved the area occupied by each of the four measured concentra tions was measured by a planlmeter for 100 randomly selected explosions. The area was multiplied by their duration and the velocity of the water. If the velocity of the water is taken as 6 ft/sec (180 cm/sec) an average of that reported for the inner surf zone and swash zone under similar wave conditions and beach slope by Demarest (1947), Miller and Zeigler (1958), Dolan and Perm (1966), Dolan, Perm and McArthur (1969), a mean of 189,783 gms per sand fountain is obtained or about 0.1 yds^. On the other hand, if 4 ft/sec Is the average velocity as reported by Schiffman (1965) and Brenninkmeyer (1968), then 127,154 153 gras or 0.06 yds^ are moved per lofted cloud. This latter velocity is approximately the same as the water velocity based on solitary wave theory (Munk, 1949). Measurements by Inman and others (1971) show that at the bottom the velocity of a water particle under a bore is nearly equal to that predicted whereas at the surface it may be up to 8 times faster. If the number of explosions occurring per tide are 3 cumulatively added, then between 6.4 and 10.6 yds are moved in suspension on the upper beach face per strip one foot wide. This is 3-4 times the amount reported by the Beach Erosion Board (1933) for Pensacola, Florida but about the same amount as Long Branch, Mew Jersey. After the data for each almometer is plotted between the constraints of the limit of the upper swash and the un known amount on the seaward side of the breaker zone be- tween 200 and 400 yds of sand are placed in suspension per zone one foot wide per tide. The amount on the outer fore shore drops to almost nothing seaward of the lower tide plunge point (Beach Erosion Board, 1933). The curve be tween these points is, of course, arbitrary but should have the general shape as is shown In figure 31. It can be seen that by far the largest amount of Band in suspension is transported shoreward of the high water plunge point in the transition zone. It was shown earlier that In the vicinity of the Arnold Road Beach ap- Figure 31 Quantity of sand transported in suspension per strip 1 foot wide per tide. The upper curve assumes a bore velocity of 6 ft/sec. The lower curve is for 4 ft/sec. 154 155 I I 10 9 8 7 YDS3 6 5 4 3 2 I 0 4 0 0 YDS / FT/TIDE 8 7 6 5 4 3 2 LIMIT OF U P R U S H AT ''' LOW TI DE MLLW 100 o 100 200 D I S T A N C E F R O M P L U N G E P O I N T A T H I GH T I D E 156 proximately 59 x 10^ yds^ are moved by longshore transport between the base line and MLLW. The quantity of sand thrown into suspension per year six inches above the bottom is 137-274 x 10^ yds^ or about 2-5 times that moved by longshore currents. Thus more than two-thirds of the sand in suspension at Point Mugu is not Involved in long shore transport but moves normal to the shoreline. This is somewhat lower than Inman's and Bagnold's (1963) ten fold figure, but the amount obtained should increase tremendously if the bottommost six inches are included. On the other hand, if there were strong longshore currents and their progress and the movement of sand not checked by the Experimental Groin, their velocity profile (Komar, 1971, p. 719) is strikingly similar to that of Figure 31. Observations by Inman and Quinn (1952) and theoretical relations (Bowen, 1969; longuet-Higgens, 1970) show that the longshore velocities have approximately the same asymmetrical shape as the suspended sediment distri bution. One is drawn to conclude that a large fraction of the longshore transport is by suspension. Causes of Sand Suspension in the Surf Zone The suspension clouds measured occur for at least five reasons valid for different parts of the coastal area. In the area of shoaling waves Inman and Nasu (1956) show that vertical velocities to 2 ft/sec directed down- 157 ward exist not only under wave crests "but also under wave troughs. Upward vertical velocities are highest under the wave crests. However, not all wave creBts possess an ac companying upward velocity. Morrison and Crooke (1953) note that the maximum horizontal and vertical velocities occur when the wave crest approaches. But when it is about to break the maximum vertical velocity (Iverson, 1953) is ahead of the wave front near the plunge point. The maximum horizontal velocity is almost equal to the crest celerity just shoreward of the highest part of the crest (Ippen and Kulin, 195^) after breaking or 0.09 1 after the crest (Adeyemo, 1971) depending on the slope. The distribution of the lifting forces are more than suf ficient to raise sediment into suspension. Inside the surf zone measurements by Longinov (1956, 1957, 1958a, 1961, 1964) show that discrepancies between theoretical (Airy's) and actual water velocities vary by a factor of 5 for the surface and a factor of greater than 20 for the bottom. His recordings by means of a dynamometer show that positive vertical velocities a few cm above the bottom reach 50 percent of the horizontal velocities and that higher in the water column they may reach 80 percent. The maximum vertical velocities are not randomly distributed but occur either when the horizontal velocity Is zero, changing from shoreward to seaward or just after the shoreward maximum. This perhaps explains 158 the onset of suspension that has been observed when the horizontal velocity decreases (Martin, unk.; Inman, 1965; Palmer, 1970). A look at Figure 32 (Longinov, 1964) shows the hori zontal pressures across the surf zone. The three dynamo meters are placed Just above the bottom; C-^ is in the swash zone, Cq at the still water level, C-j on the seaward side of the breaker zone. Note that the maximum velocities both seaward and landward occur at the still water level. At the plunge point and at the inner breaker line when the wave breaks, the wave front is saturated with air bubbles and foam which penetrate the bottom. The ascent of these bubbles have a suctional effect sufficient to draw up sand (Aibulatov, 1957, 1958, 1961). Medvedev and Aibulatov, 1958, and Aibulatov, Bolyrev and Griesener, 1961, note that in this zone the descent and rise of air laden water causes continuously changing vertical eddies. The two in combination stir up a cloud of sediment which may be several meters wide and last several seconds. In the Black Sea these clouds reach a height of 20-30 cm. The dearth of sand fountains near the primary breaker suggests that the air bubbles do not reach the bottom but are absorbed in the surficial water layers. Even secondary breakers in the lower surf zone do not ap pear to be an effective lifting agent. However, close to shore uplifts because of the entrapped air may be very ef- Figure 32 Changes in horizontal water velocity across the inshore and foreshore. (After Longinov, 1964) 159 Profile No. 7 C - l Profile No. 8 C-3 C-Z — f , J b(7 3 0 3 B aec Records* of water levet and pressure changes, weak wave action on a steep foreshore G ”l | e -2, and c*3 " V O K Instrument racords; Pc*3 * * wave meter record; ■ > * * direction of wave propagation; — — --------- iero pressures. 160 161 fectlve In lofting sand above the bottom. Miller and Zeigler (1958, 1964), Ingle (1966) and Ippen (1966) suggest another reason for the suspension clouds. The water circulation in the surf zone depends upon the relative timing of the arrival of the incoming bore and the backruBh from the previous surge. When the two are coincident there is little exchange since the breaker is formed primarily from the water going back to the sea. Horikawa and Kuo (1967) have shown that the breaking limit of a solitary wave (H = : 0.78h) is not suit able in the surf zone and that deep water wave steepness has little influence on wave instability in this zone. Thus the inner breakers may be caused by the return flow of the backwash. Pressure profiles (Pig. 32; also Schiffman, 1965a) in the surf zone show surge profiles that increase gradually, reach a maximum and then decline so fast as to be almost instantaneous. If a backwash has a velocity greater than (gh)1^2 the incoming bore cannot progress against It, resulting in a hydraulic Jump or roll wave (Grant, 1943). If 6 ft/sec is the average backwash velocity, the water depth at which the Froude number be comes critical is Just under a foot. The breaking of a roll wave appears to be similar to a standing wave (Simons and others, 1965; Allen, 1968) except that it is formed by opposite flowing water masses. In the breaking of a stand 162 ing wave there is a brief suspension of much sediment, then the water and sediment movement very nearly stops (shown by zero horizontal pressures) and most of the sus- pendeds fall back onto the bed. The deposit of these sus- pendeds may well form the inner rough facies (Clifton and others, 1971) composed of steep-sided symmetrical ripples on steep beaches or the ridges and runnels (King, 1959) so common at the level of slack tide on flat beaches. These surface protuberances on their own may cause more suspen sion by creating a barrier to the backwash flow and again setting up a hydraulic jump (Li and Lam, 1964). Some of the suspension clouds may be computer intro duced. Because of the mode of digitization only the high est reading for a given concentration is utilized. If a sediment-laden backwash moves over a clean Incoming bore, the digitized results will indicate an upheaval of bottom sediment, which is not the case. It belies the assumption used in digitization that the sediment concentration would increase downwards. That overtopping by the backwash does occur has been observed on the beach (Miller and Zeigler, 1964) and is strongly suggested by Figure 18. In playing back four analogue tapes 10-15 percent of the so-called sand fountains are due to an increase of the 135 g®/l concentration at a level somewhere above the bottom and a decrease In sediment concentration below it. Overtopping, of course, Is not the only means for this inverse concen- 163 tratlon gradient. A roll wave may give a similar effect. Finally some of the suspension clouds may be due to the almometer Itself. If the suspensions of the primary vortex are carried past the station by a reversal in velocity, a spurious sand fountain will result. A good small-scale view of a roll wave is shown in Appendix. SAND MOVEMENT ACROSS THE SURF ZONE Occasionally a single surge can be followed across a portion of the surf zone. Only infrequently is the same bore detectable with certainty across all three stations. This lack of traceability can be due to the breaking of the waves between stations and thereby losing their identity or the sediment can be in such a state of up heaval that the juxtaposition is obfuscated or sediment is not readily moved throughout the breadth of the surf zone. In order to ascertain the respective modes of sedi ment transportation by bores and backwash, several samples will be cited. The similarity between A and B (Fig. 33) is clear. If the initial disturbances are taken for comparison, the backwash traveled 5.8 ft/sec. Either this velocity was not sufficient or there was a lack of turbulence for on the upper beach face (#3) the 135 gm/l suspension cloud reached 36 cm above the bottom whereas by the time it reached the lower beach face (#2) it was only 21 cm above the bottom. This is usually the case. In Figure 34- the elevation of suspended movement increases from 11 cm to 25 cm above the substrate, but this time the water velocity 164 Figure 35 Two minute record of elevation changes across the foreshore (I), lower beach face (II), and upper beach face (III) of the 135 gm/l con centration during the seaward traverse of a backwash. Uote the change In vertical scale October 1 22:00. Ebb tide 3.3 ft. Breaker height 3.5 ft, 13 seconds period 40 percent plunging, approaching land at a 5° angle from the west. 165 1 c m c m c m 60 40 30 20 0 60 40 30 20 0 60 40 30- 20 0 ~ \ * Sr- 1 H . — V v - — 1r — r \ - f ~ \ r \ 20 * id _£ r: r [ \ A / A 40 60 80 sec onds 100 166 ^ Figure 34- Two minute record of elevation changes across the foreshore (I), lower beach face (II) and upper beach face (III) of the 135 gm/1 con centration showing an increase in suspension as a backwash moves seaward. Note the change in vertical scale September 30 23:39* Ebb tide 1.4 ft. Breaker height 4 ft, period 12.5 sec. 60 percent plunging, approaching land at a 10° angle from the east. 167 sec onds ro *- f- f- § § * - ■ ■ £ > ■ fc iJ t) r } si j 3 * < ■ |I 1 \ t< h ~N j’ M - J 1 £ { j - * l — _ * ' £ - • P - I / " u * j - ‘ l f c c a ? S )_1 C_ _„ < r ’ s ! < I ? X t s r1 > — 7— 1 r1 891 169 was at least 8.3 ft/sec. It is assumed that the sand fountain cloud on the foreshore (#1) is due to the back wash for both clouds start abruptly and have a slower de nouement. It is conceivable that a surge forming the suspension cloud at station one is the same that produced the cloud near station two 33 seconds later but the shapes do not match and the water velocity would be 3.5 ft/sec, a little slow considering that the still water level is 2 ft above the surface at the foreshore station. In general the suspension clouds entrained by the backwash are of longer duration closer to shore. The same is true of those due to the uprush. But on the incoming surge the identity of the suspension clouds is frequently lost in the traverse across the inshore and foreshore. Figure 35 is a case in point. The incoming bore seems to be composed of two separate fluzes. These become even more disjoined as they move across the beach, in the pro cess losing much of their capacity to carry sand. Figure 36 shows a situation when the rising tide was 2.7 ft high and the average swash reached 180 ft from the base line (3.8 ft in elevation). An incoming bore spurted sand into a cloud 19 cm high and lasting 7 seconds, in the process depositing 2 cm of sand. When the surge reached the second station 8 Beconds later, the height of the 135 gm/l sand movement had decreased to 9 cm but gained 9 seconds in duration. Note that here too after Figure 35 Two minute record of elevation changes across the foreshore (I), the lower heachface (A), and upper beachface (B) of the 135 gm/l con centration under an incoming bore. Note changes in vertical scale. September 30 05:24. Flood tide 3.2 ft. Breaker height 2.5 ft, 13 sec, period, 25 percent plunging, ap proaching land at a 20° angle from the east. 170 171 sec onds Figure 36 Two minute record of elevation changes across the foreshore (I), the lower beach face (II), and upper beach face (III) of the 135 gm/1. concentration under an incoming bore. Note changes in vertical scale. September 30 05:24. Flood tide 3*2 ft. Breaker height 2.5 ft, 13 sec. period, 25 percent plunging, ap proaching land at a 20° angle from the east. 172 173 > r * * ? n t • ? m* m . < £ — c - 4 ' 4 i t - t - f ef “ T t - - J J ■ ^ 1 T • —c - i L 3 —* v !u— r jr - 4 £— — - —r - 3 J--- ■ » - 7 — 1 co CM 174 the surge had passed 2 cm were deposited. By the time the bore reached the upper beach its identity is masked. If its influence is first recognized at A, then the velocity would be 9*5 ft/sec which seems fast for its velocity on the lower foreshore was 10 ft/sec. If on the other hand its sway is detected at B, then the average velocity of the surge between stations two and three is half that between one and two. If the wave hits station three at 0, its velocity is 3.6 ft/sec; if at D, 2.8 ft/ sec. Each of these is possible but 3.6 ft/sec is favored because the cloud commencing at D has a slow demise which, as seen, tends to indicate a backwash phenomenon. The same Is not true for the one beginning at B. One fact worthy of note in this diagram is the continuous agitation of the sand surface at the upper beach face compared to that of the lower beachface and shore- face. In the 2 minute record depicted, only one major disturbance In the seaward stations is recorded whereas at least eight are shown in the shoreward station. This Is a common occurrence especially when the upper beach face is in very shallow water. Here the still water level is still 10 cm below the sand level at station three and the average swash reached a height of 25 cm above it. At the same time the 135 gm/l sand concentration attains a height of 19 cm above the bottom, showing that in the transition and swash zones the whole water column can be 3.75 saturated with sediment. The inequality of sediment movement across a beach is brought out even more clearly if different concentra tions are considered. Figure 37 shows this well. It is fairly typical of middle tidal phase. The rising tide still water level is 3.6 ft, breakers are approximately 3 ft high with a 12 second period. The average swash reaches a height of 5.6 ft above MLLW. In the foreshore area the 375 gm/l concentration Is, although changing constantly, varies a maximum of 6 cm. The AO gm/l concentration level changes only A cm. Note that in the upheaval the heaviest concentration reaches a height almost equal to that of the lighter concentrations. At the same time the lower beach face is more pas sive. The uplifts of sand are barely differentiable 16.3 seconds after they occurred at the seaward almometer (a velocity of 6.A ft/sec). Beside that instant the 375 gm/l concentration fluctuated only 2 cm. Four to 6 cm above it the lower concentrations show variations of about the same magnitude. The upper beach face (#3) is quite active. Nine uplifts of sand occur. Yet only in one is the heavy con centration lifted 11 cm above the bottom. The other times it is almost not affected. Before or Just after the up lifts, erosion occurs. Take the couplet A and B. Just before the arrival of A there is erosion of the substrate Figure 37 Sand fluctuations throughout the beach: September 29 05*56 Breaker Ht 3 ft. Period 12 sec. Flood tide 3-6 ft. 35 percent plunging approaching land 10° from east. Two minute record of elevation changes across the (I) foreshore, (Hi)lower beach face, (III) upper beach face. 1. 135 gm/l, 2. 75 gm/l, 3. 40 gm/l. 176 * * w » * m a • 3 • * * * ■Hi | 1-4 4 I I F= I I I I T T T T T T I i i 44= TTT 4 4 TT T T T 111! ±t n n > i i i l r. T T * \ "j i t e r -u-L 4 4 35 4- L i i i i J4 414.1 4 - 4 - 4 - i± J - l . L f t 44 I I L ' VT - T - r t i I I 4444- 4 4 0 4 L .L I .l. £G 44 i I T i i i TT t T EE u_ -r&T 44 I l M J-L I M I m J - L i i I 2 T T T " T T T i 1 1 in T T El = E $ T T I ! 1 I I ! i _ L 444 . . u T? J_L 4 4 -m- El 4 4 , J-LT3- 444: 4 — 4? 44 n ii-U-! 44 T T I I ! I ; m TTT di T T J4 EEE J-444 tcn - 4 t f 1 1 I iTTT t m 4 4 4 4 ■ M - 1 - I IX 4 4 4 4 I I ■ - 4 X TT 4 4 . i .14. 4 4 4 J ___ J 4 4 EEE- idET 4 4 44 177 178 to a depth of 6 cm without any concommitant Increase In the height of the lighter concentrations. It is thought that this erosion is due to a secondary breaker. With the pas sage of several seconds a cloud of suspendeds billow up wards. The time of its uplift and demise is symmetrical. Seven and a half seconds later another suspension cloud moves past the station. Now the cloud tapers off more gradually. It seems likely that A and B represent an In coming bore and Its backwash. At high tide (Fig. 38) the record looks different. Outside the breaker zone (#1) each passing wave leaves its trace. Each disturbance is 13 seconds apart which is the wave period. There are several times when there are up to 3 other uplifts between the wave period. These may be due to shorter period waves or since this is the outer rough facies (Clifton and others, 1971) composed of lunate megaripples, as Homma and others (1965) have shown, then usually 3 suspended peakB per wave exist close to the bottom above a rippled surface. Note the similarity In movement of the three con centrations which are seldom more than 4 cm apart. On the lower foreshore (#2) located at this time in the outer surf zone the separation between the 40 and 75 gm/l concentra tions is practically nil whereas between them and the 375 gm/l concentration a distance of 6 cm Is common. In this zone there is no strong suggestion of sand transport as- Figure 38 Two minute record of elevation changes across the foreshore (I), lower beach face (II) and upper beach face (III) of three sediment con centrations 375 gm/l (l)f 75 gm/l (2), and 40 gm/l at high tide. September 30 19:54* High tide 5*3 ft. Breaker height 2 ft, period 13 sec. approaching perpendicular to shore. Average swash reaches 120 ft from the base line. 179 180 I*. I l l I*. - * - -- ------- — _ --- — — — "t — — — : i _1 4 4 1 1 1 ----- — — — — ----- -- — .1 . iH -H - r l~r r urr -- — --- . 1 . -- ------- ... - — — --- - ---- — s -- t l l :it I - " A !l T - 1 " - T - ~ f ■ r-|- I ; -1 - 1 " 7 ‘ ’ T i j i : ■ i “I i - nr' — - " i1 ~ -~p 4 i r “ nr 1 XT i.i_ n 414 r ? ! f - H+th iil :n iT ; 1 i . L . J. i 4 j. .In. — i . l i i i 4 -i i .... L - j..i. .1 - tlji i ■ :3: j 4 . . * _ . 8 H i - 1 _ _: il 4 :Li_nr :irJ; ■rpTl i m IB# q±pp . . . . — It. It. It. ; nfo ix: GUT tttei 181 sociated with the wave period. In the inner part of the surf zone (#3) the familiar uplifts are commencing. Here the difference in elevation between the measured concentrations is never more than 4 cm. Note that the 375 gm/l surface outside the time of uplifts stays almost constant whereas in the transition zone (#3» Pig. 37) that concentration shows rapid elevation changes. At low tide (Pig. 39) the center of suspension shifts to the lower beachface. Station two now experiences many explosions while at three at the very top of the swash zone only occasionally does the incoming swash change the packing density slightly as indicated by the small drops In elevation of the sand surface which rebounds to its previous height almost immediately. On the upper foreshore (one), which at this time is under the middle surf regime, the three concentrations are almost coincident. Even in the transition zone (two) the levels of the different concentrations outside the times of the sand fountains are almost the same. Spectral Analysis A good method of measuring the similarity between any two periodic functions is to multiply them together ordinate by ordinate and to add the products over the duration of the wave form (Wastler, 1963). In autocovari- Figure 39 Two minute record of elevation changes across the foreshore (I), lower beach face (II), and upper beach face (III) of three sediment con centrations 375 gm/l (1)> 75 gm/l (2), and 40 gm/l at low tide. October 2 00:02 Ebb tide 1 ft Breaker height 3 ft, period 13 sec. approaching land at a 10° angle from the west. Average swash reaches 210 ft from the base line. 182 o i t i JL W D • « ' * i I I ' i i £81 184 ance each value In the record is multiplied by another value in the same record and from the mean of the sum is subtracted the square of the arithmetic mean of the entire record. If each number is multiplied by itself the result is the autocorrelation at lag o* It is the variance as ordinarily defined in statistics. At different lags, the positive autocorrelation function of the wave form is Ar = autocorrelation at lag r = value at time t t = 0,l,2,...n = squence of values k = o,l,2,...n = lag number A feel for the nature of autocorrelation may be ob tained by considering two examples. A sine wave becomes similar to Itself whenever the time shift is an integral number of periods. Therefore the autocorrelation function of a sine wave is also sinusoidal, with the same frequency and is symmetrical about the point which represents a zero lag. On the other hand, in a broad band noise curve a very small time shift is sufficient to destroy the similarity which never recurs. Its autocorrelation function is one sharp impulse that dies out to very low values at large time lags. Thus an autocorrelation function depends not on the actual wave form but Its frequency content. To isolate the frequency components classical Fourier analysis is applied. The magnitude of the kth 185 frequency component at point i may "be written by the cosine transform CoS - <f> #C - <Xy_ 5 m ^ cos where is the amplitude of the kth frequency = " f " (Wylie, 1951) and is the phase angle measured in radians, a constant for the kth frequency = tan'l J^!S 1 t The coefficients £LK = j bye - Ak <^5 (Lanczos, 1956; Harbaugh and Preston, 1965). The value is called the'phase shift. If it is assumed that the original function is zero outside the measured Interval, then the integration from — oc tooc can be used to compute the amplitude and phase angles. The coefficients are computed £ X j i sui The variance of X. is given by (Rayn er, a 12. 1967). The addition of the estimates of variance of each frequency resolved form the power spectrum (variance spectrum would be a more apt term). As a light beam may be resolved by a prism into its component colors of dif ferent Intensity, so the variance of a time series record is resolved into its parts by spectral analysis. Two frequencies from different periodic functions may be compared. The covariance between them Is eov 6c<j) = ft ¥ 64 A., (to ^ 186 —- d^x&y~dc.^£W) - t * f c > ^ < Ck ) C*v 6tyj) Since the correlation coefficient is ^ [ then *W^=««s(^ia-^&3) " Or, the correlation coefficient between two periodic func tions at a given frequency is due only to the phase shift between them. The summation of the covariances for dif ferent frequencies is the cospectrum. This, however, does not completely describe the correlation, for a zero correlation coefficient can be ob tained if the two frequencies are shifted ^/2 radians or if one or both of the functions have no amplitude. Another covariance measure is introduced, one shifted by 7T/2. Or fa ^ - feOOA'j _ axfr) qjfra A set of out-of-phase covariances is the quadrature spec trum. Together the co- and quadrature-spectra give the cross spectrum • — ACk) -+ J|^ where the phase difference is = fa to= The cross covariance term A x*$(K) divided by its standard deviations gives a new correlation term: 6$ ~ A*s (^/a^Ck) A^Ck) The foregoing applies only to truly periodic data. For nonperiodic data most workers follow the methods 187 developed by Tukey (1949) and Blackman and Tukey (1958). The theory presented by them essentially follows the just presented outline with three important additions. (1) Ad justments are made.by means of a spectral window or filter to negate the fact that the sample is finite in length. (2) Leakage or influence of large-scale fluctuations in the final spectrum on neighboring frequencies is diminished by prewhitening. Finally, (3) the estimates of variance is in frequency bands rather than lines. In the correlation between nonperiodic data follow ing the work of Goodman (1957)» Bendat (I960), Jenkins (1961, 1965)» Jenkins and Box (1966) and Bingham and others (1967)» the autocorrelation functions are subjected to both cosine and sine transformations to yield estimates of power and co- and quadrature-spectra. These are com bined as before to give the coherence function (i)x^. The coherence function is the correlation between the different frequency bands of the two data sequences. The power spectra computed from 6000 data points covering a 20-minute period using Dixon's (1967) BMD 02T program which detrends the data and Hamm's the spectrum manifest three diverse forms. The most common has the great majority of power in the low frequencies (less than 0.2 Hz) (see Appendix IV and Fig. 40). Much less prevalent are the spectra where the preponderance of power is In the Figure 40 Power spectrum of the 70 gm/l sand concentra tion in the inner surf zone. 188 BEST PROGRAM - PSO TEST DATE 7 1 1 0 0 2 TRK 6 2 5 PCT i . S O C H ) — f O O O O l 0.2000 O.'iOQO 0,4000 FREQUENCY - HZ a.aooo l.0400 1.2000 190 middle frequencies (Fig. 4l) with periods of less than a second. Frequently the variance is split between these ranges. In between from 0.2Hz to 1Hz and especially be yond 1.25Hz there is little power in all cases. Only rarely does the spectrum display a Dirac delta or impulse function (Fig. 42) if the station is underwater. Since the Fourier transform of a constant is a delta function (Jen kins and Box, 1966) this form is to be expected only when a station is above the swash line. Figure 4j shows a truncation of the typical 40 gm/l concentration variance spectrum for the inner surf zone and Figure 44 the bedload spectrum for the same station. Note that the predominant 0.86 second period in the heavy concentration is not present in the light concentration. It is diminutive in the 135 gm/l concentration spectrum and absent in the TO gm/l spectrum. The only time that this period is of real importance in the light concentra tions is ;}ust outside the breaker zone (see Fig. 41) where it is the only secondary frequency present. The signifi cance of this frequency is somewhat mystifying. It prob ably represents small period movements superimposed on the longer period pulses. Yet every time that a short periodicity occurB anywhere in the surf zone, it is in this 0.8-0.9 frequency band. For short period movements one would expect a rage of frequency bands but this is not the case. It may be a fundamental mode of short term Figure 4-1 Power spectrum of the 40 gm/l sand concentra tion in the offshore zone. 191 BEST PROGRAM - PSD TEST DATE 71 1 0 0 1 TRK 7 10 PCT 1.0000 MOOO 1,0000 MOM 6,0000 5,6000 9.0000 MOOO 9 . 0 0 0 0 3.5000 3.0000 1.5000 1 . 0 0 0 0 1.5000 1 . 0 0 0 0 0.5000 0 ! a 1 i I n V r t r t t k - i . w V j l V A A ' A , i ! [ 1 - J M C O I 0.1000 O.tOOO O.frQOQ FREQUENCY - HZ O.SCOO l . C Q O O 192 Figure 48 Power spectrum of the 375 gm/l sand concentra tion in the outer surf zone. 193 BEST PROGRAM - PSD TEST DATE 7 1 1 0 0 2 TRK 7 9 0 PCT 3.0000 3.0000 2.0000 1.5000 I .0000 0.5000 • 0.5000 -i.oooo - 1.5000 -2.0000 - 2.5000 -3.0000 1 I J ,il_ ■ '■ I W lH i • I n 'mwn^ '.rrrt" i n k ' , (irriM tn ^ I ’ O 'l A i V r L 1 i'jill 1 [ 1 -pool 0.2000 O.sOOO o.tooo FREQUENCY - HZ 0.9000 i.oooo 1.2000 ■>761 Figure 43 Power spectrum of the 40 gm/l sand concen tration In the inner surf zone. 195 BEST PROGRAM - PSD TEST DATE 7 1 1 0 0 1 TRK 5 10 PCT 1.5000 2.5000 2.0000 ' , | VljA 0 0.2000 -fOCOOl FREQUENCY - HZ H V O o\ Figure 44 Power spectrum of the 375 gm/l sand concen tration in the inner surf zone. 197 BEST PROGRAH - PSD TEST DATE 71 1 0 0 1 TRK 5 9 0 PCT 3.0000 3.0000 2.3000 1.3000 i . oooo J l W d aAa> . ' 0 -fO O O O l FREQUENCY - HZ 199 movement. An amplification of the shorter frequencies is shown in Figures 45-47. These show the spectra for the variations of the lightest (40 gm/l) and heaviest (375 gm/l) sand concentrations measured for the three stations and the deep water wave spectra for three tidal stages. The sediment movement frequencies were averaged to fit the frequency bands of the deep water waves. Hote that the 2 power of the sediment movement in cm is a tenth of that 2 of the waves in ft . Even with a ten-fold increase the power of the sand movement in any frequency seldom attains that of the deep water waves. In each set the coherency between the waves and sediment movement is extremely low (0-0.2) in the middle and longer frequencies. It improves somewhat (0.2-0.4) for the shorter frequencies of the 375 gm/l concentration In the breaker zone and outside the breaker zone and for both concentrations in the transition and swash zones. It ap pears, therefore, that especially in the outer and inner surf zones sediment movement is virtually Independent of the deep water wave period. This non-dependence is probably due to the small amplitude of the sand spectra or to non-linear dependencies. There are, however, some features of the spectra that bear investigation. Outside the breaker zone only the heaviest sediment concentration is somewhat Influenced by Figure 45 Wave and 40 and 375 gm/l spectra lor the outer and inner surf and swash zones. The sand spectra power has been multiplied by a factor of ten. October 2: Beginning at 15:21, flood tide 2.0 ft. Wave height 2.5 ft, waves approaching land at a 5° angle from the west. Wave spectra courtesy of the U. S, Army Corps of Engineers. 200 A 1 5 C 1 0 2 3 .2 . 3 ~r .2 ~ T . 3 FREQUENCY Hz 201 Figure 46 Wave and 40 and 375 gm/l spectra for the breaker, middle surf and still water level zones. The sand spectra power has been multiplied by a factor of ten. September 30: Beginning at 5:41, flood tide 3.5 ft. Wave height 2.5 ft, waves ap proaching land at a 20° angle from the east, Wave spectrum courtesy of the U. S. Army Corps of Engineers. 202 S P E C T R A WAVE GRAMS. LITER 375 A 15 C 1 0 . 3 .2 .1 3 2 3 1 F R E Q U E N C Y Hz 203 Figure 47 Wave and 40 and 375 gm/l spectra for the offshore and outer and Inner surf zones. The sand spectra has been multiplied by a factor of ten. October 1: Beginning at 17:57, high: tide 5 ft. Wave height 3 ft, waves approaching land at a 20° angle from the west. Wave spectrum courtesy of the U. S. Army Corps of Engineers. 204 5 0 4 0 V A R I A N C E 1 0 F R E Q U E N C Y Hz 205 206 the waves. Inside the breaker zone the bottom sediments have a periodicity of movement that equals that of the main swell and also the local sea. The light concentra tions lag somewhat behind the predominant swell period and is little effected by the sea. In the surf zone almost all the power in both the light and heavy sand water mixtures is centered on the very long periods. There is nary a reflection of the swell period in the heavy concentration. The light concentrations do somewhat better. The sea periods are even less represented in the sediment movement. The long periods may represent the largest of the waves in each group of breakers or constructive interference of both swell and sea or reflection from the experimental groin in the study area. Or the long periods may signify that not every wave moves sand. Also, the backwash may be dominant Inasmuch as especially for the bed load the periodicity seems to increase seaward. In the transition and swash zones the main swell period reappears in both concentrations with approximately a three-second lag. This undoubtedly represents a retardation in the incoming bore and coincident with it the backwash period. The presence of the local sea waves Is barely detectable since these have dissipated their power before reaching the transition zone of the longer swell waves. Until further studies are undertaken to ascertain the movement of water in the surf zone and their relation 207 ships to the deep water waves and their bearing on sedi ment movement only the most general statements can be made with any certitude. Only with measurements of the water movements that are as detailed as those now available for sand motion can the sedimentation patterns in the surf zone be more clearly understood. CONCLUSIONS Acknowledging the limitations in this study result ing from imprecision in calibration of the almometer, plus its influence on the vicinity around the instrument and the dearth of knowledge of the mechanism of sand transport in the surf zone, the following conclusions, divided into four parts, are proposed. Instrumentation; 1. An Instrument, an almometer, now exists which simultaneously measures sediment concentrations at each of 64 points In a vertical column. This portable and relatively easily installed machine consists of two parts: (l) an acrylic cylinder containing a high intensity flourescent lamp, and (2) a cylinder with a stacked series of photoelectric cells. 2. The limits of measurable sediment concentration in the present configuration ranges from 10 gms/l to 900 gms/l. The size distribution and composition of the sedi ment must be known prior to installation for they can affect the calibration. 3. The measurements are made by a time sweep of each of the 64 sensors at any predetermined discrete time interval. The output Is in analog form but is fully con- 208 209 sistent with binary logic so that any recording method can be employed. 4. If the two parts are placed close together or their diameter increased, an almometer can be used to quantify in situ scour phenomena. Sediment Distribution: 1. The mean sand size in the middle of the swash zone as it migrates across the shore and beachface with the side is smallest near the mean low water mark. It Increases slightly seaward and rapidly landward. 2. The mean sediment size at the Arnold Road Beach at Point Mugu may be predicted by the curve Md = 0.296 -1.17 X 10~^ (distance from baseline (ft)) + 2.0 x 10”^ (distance from baseline (ft))2. 3. On the ebb tide, sand in the swash zone is coarser than on the flood tide. 4. The skewness measure of the sand in the swash zone becomes negative on the ebb tide and positive on the flood tide. Only when the tidal inequality is small is this not true. Topography Changes; 1. Deposition and erosion during a tidal cycle shows six general stages: deposition when the swash first reaches an area, erosion under the transition zone, de position near the high tide slack water, erosion again with the return of the transition zone, deposition within 210 the swash, and finally a minor amount of erosion before the area Is above the swash limit. 2. The net elevation change in erosion and deposi tion in general increases seaward. Deposition prior to high tide is less than thereafter. The reverse is true for erosion. 3. The average occurrence of these phases before and after high tide is nearly symmetrical around that time point. The deposition at high tide generally takes place before the peak of the tide. Although the symmetry holds for averages of 20 tidal cycles, individual occurrences cannot be predicted at this time. 4. The net average change in topography per tidal cycle under non-storm conditions is small. At Point Mugu it is less than half a centimeter except for the berm crest when that was attacked by spring tides. 5. The average depth of erosion at Point Mugu is about 14 percent of the breaker height on the foreshore decreasing to 6 percent on the beach face. No meaningful correlation exists between the breaker height and depth of erosion. 6. Offshore winds are a paramount factor in in creasing the amount of erosion or deposition in a tidal cycle. Offshore winds depress the usual tidal cycle deposition and increase the erosion. When the wind abates its effects are rapidly erased. 211 7• On a term crest reached by spring tides the first change in topography is erosion and only then does deposition of the magnitude of 3-4 cm take place. There is no high tide deposition on a berm crest. 8. More than half (28 cm) of the total (55 cm) loss in berm elevation occurred in a half an hour before the peak of the first high tide. This depletion was not constant but took place in a series of large steps. The trend was frequently reversed by deposition. Sediment Movement: 1. The motion of sediment in the inner and outer surf zones is virtually independent of the deep water wave periods. In the other zones the dependency improves some what but not sufficiently to make predictability practic able . 2. Most of the variance of the sand movement is concentrated in frequencies of less than 0.2 Hz and be tween 1.15 Hz and 1.25 Hz. The longer periods are due to the predominant swell, constructive interference of swell and sea, reflection from the experimental groin, the longer periods of the backwash and the incapacity of every incoming wave to transport sediment. The shorter period seems to be a fundamental mode of fast movement super imposed on the longer periods. 3. Modes and frequency of sand transport differ within each of the dynamic zones of the coastal area. 212 a. Outside the "breaker zone sand moves pre dominantly by bed load in pulses coincident with the prevailing swell period. A shorter periodicity may prevail in the presence of ripples. Movement of sand more than 10 cm above the bottom is rare. The average sand surface elevatlon-changes-per-wave ranges from 0-6 cm. b. Inside the breaker zone sand moves more rapidly with frequencies equal to that of the main swell and sea periods. The sand surface changes swiftly with differences in elevation of more than 6 cm per wave not uncommon. Sand is rarely thrown into suspension. The suspension clouds that do occur have a rapid symmetrical rise and fall and are of short duration. c. After the transformation of the incoming wave to a bore in the outer surf zone, sedi ment movement is small. The sand surface changes no more than 4 cm with the passage of a bore. The distance between the bottom and the lighter concentrations seems to be dependent on the beach ground water level. If the outer surf zone is below the water table, the various concentrations are almost 213 coincident. If the outer sand zone Is above the water table, the 135 gm/l concentration is approximately 6 cm above the bottom. Suspension of sand more than 10 cm above the bottom Is almost nonexistent. d. In the inner surf zone suspended sand trans port increases in frequency, elevation and duration since in this area the incoming bore breaks and the zone is Influenced by the backwash. The bottom elevations are little effected by these suspension clouds. e. In the transition zone at the still water level sand movement by suspension becomes predominant. Upheavals in the sediment are frequent and show a variety of different shapes and are of various durations. The frequency of occurrence of these sand fountains show a considerable spread. Two periods stand out at Point Mugu. The first is a little longer than the prevailing swell period. The second, somewhat longer, may be due to interference or reflection or more likely to the fact that only the longest waves can reach this zone and also due to the longer period of the backwash. 214 f. In the swash zone sand movement reverts back to bedload. Transport of any quantity of sand 10 cm above the bottom Is exceeding ly rare. Flotation of sand at the shore ward margin may be important in transporting shoreward the coarser sand grains. 4. The amount of sand thrown into suspension 15 cm above the bottom for a strip a foot wide per tide is be tween 150-300 in^ or 100-200 x 10^ in^ per year. This is 2-5 times that moved by longshore currents. Most of the suspension occurs in the transition zone. 5. Sediments are suspended by means of: a. The horizontal and vertical water velocities and fluctuations in velocity are sufficient to suspend even the coarsest sand. b. Entrapped air in a breaking wave has a suctional effect after penetration of the bottom. c. A hydraulic jump or roll wave is created if the backwash velocity is sufficiently high or if ripples are present in the transition zone. references 215 REFERENCES Adeyemo, M. D., 1971, Velocity fields in the wave "breaker zone: Pro. Twelfth Conf. Coastal Engineering, Am. Soc. Civil Engineers, v. 1, p. 435-4-60. Afflfi, A. A. and Azen, S. P., 1972, Statistical analysis: A computer oriented approach: New York, Academic Press. Aibulatov, N. A., 1958, Novye issledovaniya vdol 1beregovogo peremeshcheniya peschanykh nanojjv v more: (New investigations of longshore migration of sandy sediment in the sea): Okeanograficheskoi Komlssii An SSSR Byell, v. 1, p. 72-80. ______ , 1961, Nalyudyeniya za vdolhegohyn peremeshcheniem peschanykh nanosov u otmelogo akkulyativnogo merega: (Observations of the long-shore sand drift along a shallow coast of accumulation: Akad. Nauk SSSR Inst. Okeanol. Trudy, v. 53, p. 3-18. ______ , 1966, Issledovanie vdol'beregovogo permeslichenia peschanykh nanosov v more: (Investigations of long shore migration of sand in the sea): Moscow, Nauka Publ., 159 p. ______ , Bolyrev, V. L. and Griesseier, H., 1961, Das studium der sediment bewegung in flussen und meeren mit hilfe von luminerszierenden farbstoffe und radioactlven Iso topen: Petermanns Geog. Mitt., jg., 105, heft 4, p. 117-186, 254-263. Allen, J. R., 1968, Current ripples: Amsterdam, North Holland, 433 p* Bagnold, R. A., 1954, Physics of blown sand and desert dunes: London, Methuen and Co., 265 p. ______ , 1956, The flow of cohesionless grains in fluids: Royal Soc. London Philos. Trans., ser. A, v. 249, p. 235-297. ______ , 1963, Beach and nearshore processes: Part I Mechanics of marine sedimentation: in Hill, M. N., ed., The Sea: New York, Interscience, v. 3, p. 507- 528. 216 217 Bagnold, R. A., 1966, An approach to the sediment trans port problem from general physics: U. S. Geol. Survey Prof. Paper, 422-J, 37 p. Bascom, W. N., 1951* The relationship between sand size and beachface slope: Am. Geophys. Union Trans., v. 32, p. 866-874. Bendat, J. S., I960, Measurement and analysis of power spectra and cross power spectra for random phenomena: Oanoga Park, Calif., Ramo-Woolridge Publ. M275-0U4. Bingham, C., Godfrey, M. D., and Tukey, J. W., 1967, Modern techniques of power spectrum estimation: IEEE Trans. Audio and Electroacoustics, v. AU-15, no. 2, p. 56-66. Blackman, R. B. and Tukey, J. W., 1958, The measurement of power spectra: New York, Dover Publ., 190 p. Bowen, A. J., 1969, The generation of longshore currents on a plane beach: Jour. Marine Research, v. 27, p. 206-215. Braun, G., 1911, Einige Ergebnisse Entwicklungsgeschlcht- lichen Studien an europaischen Flachlandkusten und ihren Dunen: Zeitschr. der Gesellshaft f. Erdkunde, Berlin, p. 54-3-560. Brebner, A. and Kamphuis, J. W., 1963, Model tests on relationships between deepwater wave characteristics and longshore currents: Queens Univ. Ontario, Civil Engineering Res. Rept., 31, p. 1-25. Brenninkmeyer, B. M., 1968, Sedimentation patterns in the lower swash zone: Unpubl. report in sedimentation, Univ. Southern California, 18 p. Briggs, L. I. and Middleton, G. V., 1965, Hydromechanical principals of sediment formation: in Middleton, G. V., ed., Primary sedimentary structures and their hydro- dynamic interpretation: Soc. Econ. Paleontologists and Mineralogists Spec. Pub., 12, p. 5-16. Carstens, M. R., 1965, Part I. The effect of dunes upon localized scour: Georgia Inst, Technology, Engineer ing Exp. Station, Pinal Rept., Pro;). A-770, 19 p. ______ , 1966, Similarity laws for localized scour: Am. Soc. Civil Engineers Proc., Jour. Hydraulics Div., v. 92, p. 13-36. 218 Clairex Electronics, Inc., 1966, Photoconductive cell manual, New York, 16 p. Clifton, H. E., Hunter, R. E. and Phillips, R. L., 1971, Depositional structures and processes in the non barred high-energy nearshore: Jour. Sed. Petrology, v. 41, p. 651-670. Colby, B. R., 1964, Discharge of sands and mean-velocity relationships in sand-bed streams: U. S. Geol. Survey Prof. Paper 462A, 47 p. Cook, D. 0., 1969, Calibration of the University of Southern California automatically recording settling tube: Jour. Sed. Petrology, v. 39, p. 781-786. ______ , 1969, Sand transport by shoaling waves: Univ. Southern California, unpubl. dissertation, 148 p. Cooley, J. W. and Tuckey, J. W., 1965, An algorithm for the machine calculation of complex Fourier series: Mathematics of Computation, v. 19, p. 297-301. Cornaglia, P., 1881, Du flot de fond dans les llquides en etat d'ondulation: Annales Ponts et Chaussees ______ , 1889, Sul regime della Spiaggie e sulla regola- zione dei porti: Turin Cornish, V., 1889, On sea-beaches and sea-banks: Geog. Jour., v. 11, p. 528-543, 628-651. Curtis, C. M., 1963, Suspended sediments in a breaking wave: Univ. Southern California, unpubl. report on sedimentation, 19 P- Demarest, D. F., 1947, Rhomboid ripple marks and their relationship to beach slope: Jour. Sed. Petrology, v. 17, p. 18-22. DeMartonne, E., 1926, Traite de geographie physique: 4 ed. Paris, A. Colin, v. 1, 910 p. DeVIolini, R., 1967, Climatic handbook for Point Mugu and San Nicolas Island, Vol. I, Surface data: Pacific Missile Range Misc. Rept., PMR-67-2, 156 p. 219 DeViolini, R., 1970, Tidal and lunar data for Point Mugu and San Nicolas Island and the Barking Sands Area during 1971: Pacific Missile Range, Tech. Bull., PMR-TP-70-4, 65 p. Dixon, W. J., 1967, BMD Biomedical computer programs: Univ. of California Press, Los Angeles, 600 p. Dolan, R., 1965, Seasonal variations in heach profiles along the Outer Banks of North Carolina: Louisiana State Univ., Coastal Studies Inst., Tech. Rept., 27 Part A, 5 p. ______ , Perm, J. C. and McArthur, D., 1969* Measurements of heach process variables, Outer Banks, North Carolina: Louisiana State Univ., Coastal Studies Inst., Tech. Rept., 64, 79 p- ______ and Perm, J., 1966, Swash processes and beach characteristics: Prof. Geographer, v. 18, p. 210-213. Drake, D. P., 1972, Distribution and transport of sus pended matter, Santa Barbara Channel, California: Univ. Southern California, 342 p. DuBoys, M. P., 1879, Etudes du regime du Rhone et l1action excercee paries eaux sur un lit a fond de graviers undeflnltment affouillable: Annales Ponts et Chaussees, ser., 5* v. 18, p. 141-195* Duncan, J. R., 1964, The effects of water table and tidal cycle on swash-backwash sediment distribution and beach profile development: Marine Geology, v. 2, p. 186-197- ______ , 1965, Textural analysis of swash-backwash sands deposited during a semi-diurnal tide cycle: Oregon State Univ., unpubl. report in oceanography, 16 p. Eagleson, P. G., Dean, R. G. and Peralta, L. A., 1957, The mechanics of the motion of discrete spherical bottom sediment particles due to shoaling waves: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 104, 41 p. ______ , Glenne, B. and Bracup, J. A., 1961, Equilibrium characteristics of sand beaches In the offshore zone: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 126, 66 p. Egorov, E. N. and Popov, B. A., 1958* Opyt suoruzhyeniya podvyesnoy kanatnoy dorogy dlya yezuchenya dvyzhenya nanosovu porskykh beregov: (Experience gained in the construction of an overhead cable way to study the movement of material on the shore): Akad. Nauk SSSR Inst. Okeanol. Trudy, v. 28, p. 30-37. Einstein, H. A., 1942, Formulas for the transportation of bedload: Am. Soc. Civil Engineers Trans., v. 107, P* _______, 1950, The bedload function for sediment transpor tation in open channel flow: U. S. Dept. Agriculture Tech. Bull., 1026, 70 p. _______, 1964, River sedimentation: in Chow, V. T., ed., Handbook of hydrology: New York, McGraw-Hill, sec. 17, p. 35-67. _______ and Abdel-Aal, F. M., 1972, Einstein's bedload function at high sediment rates: Am. Soc. Civil Engineers, Jour. Hydraulics Div., HY 1, v. 98, p. 137- 151. _______ and Chien, N. , 1954, Second approximation to the solution of the suspended-load theory: Univ. Cali fornia Inst. Engineering Res., no. 3. Emery, K. 0., 1945, Transportation of marine beach sand by flotation: Jour. Sed. Petrology, v. 15, p. 84-87. _______, 1961, A simple method of measuring beach pro files: Limnology and Oceanography, v. 6, p. 90-93- _______ and Poster, J. P., 1948, Water table in marine beaches, Jour. Marine Research, v. 3, p. 644-654. _______ and Gale, J. P., 1951* Swash and swash marks: Am. Geophys. Union Trans., v. 32, p. 31-36. Evans, 0. P., 1938, Sorting and transportation of material in the swash and backwash: Jour. Sed. Petrology, v. 9, p. 28-31. _______, 1942, A discussion of the use and meaning of the term low and ball: Jour. Geology, v. 50, p. 213-215* Fairchild, J. C., 1959, Suspended sediment sampling in laboratory wave action: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 115, 25 p. 221 Fairchild, J. C., 1971, Suspended sediment concentration in the surf zone: Am. Geophys. Union Trans., v. 52, p. 260. Fausak, L. E., 1970, The beach water table as a response variable of the beach-ocean-atmosphere system: Virginia Inst. Marine Science unpubl. thesis, 52 p. Federal Interagency Sedimentation Project, 1970, Project accomplishments during calendar year 1969; mimeo. Felix, D. W., 1969, An inexpensive recording settling tube for analysis of sands: Jour. Sed. Petrology, v. 39, p. 777-780. Fleet Weather Facility, 1971, Climatological study Southern California operating area: San Diego, U. S. Naval Weather Service Command, 240 p. Fukushima, H. and Mizoguchi, Y., 1958, Field Investigation of suspended littoral drift: Coastal Engineering in Japan, v. 1, p. 131-134. Galvin, C. J., 1967, Longshore current velocity: A re view of theory and data: Rev. Geophysics, v. 5» P* 287-304. Giese, G. S., 1966, Beach pebble movement and shape sort ing indices of swash zone mechanics: Univ. Chicago, unpubl. thesis, 65 p. Gilbert, G. K., 1885, The topographic features of lake shores: U. S. Geol. Survey Fifth Ann. Report, p. 69- 123. ______ , 1890, Lake Bonneville: U. S. Geol. Survey Mono graph, v, 1, 438 p. Goodman, N. R., 1957, On the joint estimation of the spectra, cospectrum and quadrature spectrum of a two dimensional stationary gaussian process: New York Univ., Engineering Statistics Lab., Scientific Paper 10, 168 p. Graf, W. H., 1971, Hydraulics of sediment transport: New York, McGraw-Hill, 513 p* Grant, U. S., 1943, Waves as a sand transporting agent: Am. Jour. Sci., v. 241, p. 117-123* 222; Gugnyaev, Y. E.f 1954, Laborarnoye Isslyedovaniye vzaimod- yeystvlya voln frontalnogo naravlyenlya speschanimi otkosami: (A laboratory study of the interaction be tween waves of frontal direction and sandy slopes): Akad. Nauk SSSR, Inst. Okeanol. Trudy, v. 10, p. 157- 168. Guilcher, A., 1954* Morphologle littorale et sous-marine: Paris, Presses Universitaires de Prance, 215 p. Hagen, G., 1863, Handbuch der Wasserbaukunst: v, 3, Das Meer Berlin, Gebruder Borntrager, 364 p. Hagin, J. W., 1951* The source, transportation and deposition of beach sediment in southern California: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 22, 127 p. Harbaugh, J. W. and Preston, P. W., 1965, Fourier series in geology: Arizona Univ., College of Mines, v. 1, p. 1-46. Harrison, W., 1969, Empirical equations for foreshore changes over a tidal cycle: Marine Geology, v. 7, p. 529-552. ______ , Rayfield, E. W., Boon, J. D., Reynolds, G., Grant, J. and Tyler, D., 1968, A time series from the beach environment: U. S. ESSA Research Lab Tech. Memo ERLTM-AOL-1, 85 p. Hartnack, W., 1924, Sandriffe-untersuchungen an der Pommerschen Kuste: Geogr. Gesell. Greifswald Jahrb., p. 40-42, 48-68. Hattori, M., 1969, The mechanics of suspended sediment due to wave action: Internat. Assoc, for Hydraulic Research, Thirteenth Congress, v. 3* p. 399-406. Heisenberg, W. C., 1958, The physicist's conception of nature: New York, Harcourt, Brace, 102 p. ______ , 1959, Physik und Philosophie: Stutgart, S. Hirsel, 201 p. Hjulstrom, P., 1939, Transportation of detritus by moving water: in Trask, P. D., ed_, , Recent marine sediments: Tulsa, Am. Assoc. Petroleum Geologists, p. 5-31. 223 Hoerl, A, E., 1954, Fitting curves to data: In Perry, J. E., ed., Chemical Business Handbook: New York; McGraw-ETll, Chap, 20, p. 55-77. Homma, M., Horikawa, K, and Kajima, R., 1965, A study of suspended sediment due to wave action: Coastal Engineering in Japan, v. 3, p. 85-103. ______ and Sonu, C., I960, A study of beach erosion at the sheltered beaches of Katasi and Kamakura, Japan: Coastal Engineering in Japan, v. 3, p. 101-122, Horikawa, K, and Kuo, C., 1967, A study of wave trans formation inside surf zone: Proceedings of Tenth Conf, Coastal Engineering, New York: Am. Soc. Civil Engineers, v. 1, p. 217-233* Ingle, J. C., 1966, The movement of beach sand: Amster dam, Elsevier, 221 p. Inman, D. L., 194-9, Sediment trap studies of suspended material near the surf zone: Scripps Inst, of Oceano graphy Quaterly Progress Rept. to U. S. Army Corps of Engineers Beach Erosion Board, no. 2, p. 5-6. ______ , 194-9b, Sorting of sediment in the light of fluid mechanics: Jour. Sed. Petrology, v. 19, p. 51-70. ______ , 1950, Report on beach study In the vicinity of Mugu Lagoon, California: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 14, 47 p. ______ , 1952, Measures for describing the size distribu tion of sediments: Jour. Sed. Petrology, v. 22, p. 125-145. 1954, Beach and nearshore processes along the southern California coast: California Blv. Mines and Geology Bull., 170, Chap. 5, P» 29-34. ______ and Bagnold, R. A., 1963, Littoral processes: in Hill, M. N., ed,., The Sea: New York: Interscience, v. 3, p. 529-553. ______ and Nasu, M., 1956, Orbital velocities associated with wave action near the breaker zone: U. S. Army Corps of Engineers Beach EroBion Board Tech. Memo. 79, 43 p. 224 Inman, D. L. and Quinn, W. H., 1951. Currents in the surf zone: Proc. Second Conf. Coastal Engineering: Univ. California Council on Wave Research, p. 24-36. ______ and Rusnak, G. S., 1956, Changes in sand level on the beach and shelf at La Jolla, California: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 82, 30 p. ______ , Tait, R. J. and Nordstrom, C. E., 1971, Mixing in the surf zone: Jour. Geophys. Research, v. 76, p. 3493-3514. Inose, S. and Shiraiski, N., 1956, The measurement of littoral drift by radioisotopes: Dock and Harbor Authority, v. 36, p. 284-288. Ippen, A. T., 1966, Estuary and coastline hydrodynamics: New York, McGraw-Hill, 744 p. ______ and Eagleson, P. S., 1955, A study of sediment sorting by waves shoaling on a plane beach: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 63, 83 p. ______ and Kulln, G., 1954, The shoaling and breaking of the solitary wave: Proc. Fifth Conf. Coastal Engineer ing, Univ. California, Council on Wave Research, p. 27-47. Iverson, H. H., 1952, Laboratory study of breakers: Natl. Bureau of Standards Circular 512, p. 9-32. ______ , 1953, Waves and breakers in shoaling water: Proc. Third Conf. Coastal Engineering: Univ. California Council on Wave Research, p. 1-12. Jakuschoff, P., 1932, Schwebestoffbewegung in Flussen in Theorie und Praxis: Inst, fur Wasserbau der Tech- nlschen Hochschule Berlin, Mitteil., 10, 24 p. Jenkins, G. M., 1961, General considerations in the analysis of spectra: Technometrics, v. 3, p. 133-166. ______ , 1965, A survey of spectral analysis: Applied Statistics, v. 14, p. 2-32. Jerlov, N. G., 1968, Optical oceanography: New York, Elsevier, 194 p. 225 Johnson, D. W., 1919 (1965)* Shore processes and shoreline development: New York, Hafner Publishers, 584 p. Johnson, J. W., 1952, Pinal report on sand transportation by wave action: Univ. California, Dept, of Engineer ing, Wave Research Lab. Tech. Rept. Series 14, no. 9, 6 p. ______ , 1953» Sand transport by littoral currents: Iowa Inst. Hydraulic Research, Proc. Fifth Hydraulic Conf., p. 89-109. ______ , 1956, dynamics of nearshore sediment movement: Am. Assoc. Petroleum Geologists Bull., v. 40, p. 2211- 2232. Kalinske, A. A., 1947, Movement of sediment as bed load in rivers: Am. Geophys. Union Trans., v. 28, p. 615-620. Kalkanis, G., 1964, Transportation of bed material due to wave action: U. S. Army Corps Engineers Coastal Eng. Research Center Tech. Memo., 2, 38 p. Kaplow, E. J., 1947, Oxnard oil field: California Dept, of Natural Resources, California Oil fields; Summary of Operations, v. 33# no. 2, p. 16-20. Keulegan, G. H., 1948, An experimental study of submarine sand bars: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo., 3, 40 p. King, C. A. M., 1959, Beaches and coasts: London, Arnold, 403 p. ______ and Williams, W. W., 1949, The formation and move ment of sand bars by wave action: Geography Jour., v. 103, p. 81-82. Kolpack, R. L., 1971, Physical characteristics of sandy beaches: in Kolpack, R. L., ed.., Biological and oceanographical survey of the Santa Barbara oil spill 1969-1970: Los Angeles, Allen Hancock Foundation, v. 2, p. 7-63. Komar, P. D., 1969, The longshore transport of sand on beaches: Univ. California, San Diego, unpubl. dis sertation, 143 p. ______ , 1971, The mechanics of sand transport on beaches: Jour. Geophys. Research, v. 76, p. 713-721. 226 Kressner, B., 1928, Modelverauche uber die WIrkungen der Stroemungen und Brandungwellen auf einen sandigen Meerestrand: Bautechnlk, v. 6, no. 25, p. 374-386. Lanczos, C., 1956, Applied analysis: Englewood Cliffs, Hew Jersey, Prentice Hall, 608 p. Lehman, P. W., 1884, Das Kustengebiet Hinterpommerns: Zeitschr. der Gesell. fur Erdkunde Berlin, v. 19, p* 332-404. LI, W. I. and Lam, S. H., 1964, Principles of fluid dynamics: Reading, Mass., Addison-Wesley, 374 p. Little, R. D., 1968, Suspended sediment in the surf zone: Univ. Southern California, unpubl. report on sedi mentation, 28 p. Longlnov, V. V., 1958a, Nekotorye dannye nablyudenii nad gorizontal'nymi volnovymi davleniyami v pridonnom sloye beregovoi zony v prirodnykh usloviyakh: (Some data of field observations on horizontal wave pressures in the bottom layer of the shore zone): Akad. Nauk SSSR Inst. Okeanol Trudy, v. 28, p. 100- 156. ______ , 1958b, 0 dinamike priboinoi zony i beregovoi zony v tselom: (The dynamics of the breaker zone and of the coastal zone as a whole): Llet. TSR Mokslu Akad. Geol. i Geogr. Inst., v. 7. ______ , 1958c, Opyt opredeleniya nanosodvizhushchego deystviya volnenlya podannym nablyedenii nad trans- formatsiey volny v beregovoi zone: (An experiment for determining the sediment transporting effect of waves from data obtained by observations of the transformation of waves in the shore zone): Akad. Nauk SSSR Inst. Okeanol. Trudy, v. 28, p. 157-184. ______ , 1961, Kopryedyelyenlyu maksimalnkh volnovkh skorostyey v beregovoy zone morya: (The determina tion of maximum wave velocities in the shore zone of the sea): Akad. Nauk SSSR Inst. Okeanol. Trudy, v. 48, p. 287-308. ______ , 1964, Some aspects of wave action on a gently sloping sandy beach: Internat. Geology Review, v. 6, p. 212-227. 227 Longinov, V. V., 1968, Opredelenye kontsentratii peschanykh vzvesel v beregovoi zony pri volnenii fotoelektrich- eskim metodom: (Determination by a photoelectric method of sand suspension concentration in the littoral zone during waves): Gosudarstvennyl proektno-konstruktorskll i Naucho-lssledovatel'skll Institut Morskogo Transporta (Leningrad), v. 20/26, p. 82-92. Longuet-Higgins, M. S., 1953, Mass transport in water waves: Royal Soc. London Philos. Trans., Ser. A, v. 245, p. 535-581. ______ , 1970, On the longshore currents generated by obliquely incident sea waves: Jour. Geophys. Review, v. 75, p. 6778-6801. McKelvey, V. E., 1941, The flotation of sand In nature: Am. Jour. Sci., v. 239, p. 594-607* Mann, H. B. and Whitney, D. R., 1947, On a test of whether one of two random variables is stochastically larger than the other: Annual Math. Statistics, v. 18, p. 50-60. Marlette, J. W., 1954, The breakwater at Redondo Beach, California, and its effect on erosion and sedimenta tion: Univ. Southern Calif., unpubl. thesis, 82 p. Martin, C., unk., The effect of uplift on incipient motion of bed particles: mimeo. Medvedev, V. S. and Aibulatov, N. A., 1958, Izuchenye dinamiki otmelogo peschanogo berega pomoshch'yu lyuminoforov I podvesnoi dorogi: (Dynamic studies of a shallow sandy shore by means of lumenophores and aerial tramway: Akad. Nauk SSSR Inst. Okeanol. Trudy, v. 28, p. 37-55* Meyer-Peter, A. and Muller, R., 1948, Formulas for bed load transport: Internat. Assoc. Hydraulic Structures Research Second Meeting, Stockholm, p. 39-64. Miller, R. L. and Zeigler, J. M., 1958, A model relating dynamics and sediment pattern in equilibrium in the region of shoaling waves, breaker zone and foreshore: Jour. Geology, v. 66, p. 417-441. ______ , 1964, A study of sediment distribution in the zone of shoaling waves over complicated bottom topo graphy: in Miller, R. L., ed., Papers in Marine 228 Geology: New York, MacMillan Co., p. 133-153. Moore, W. L. and Maach, P. D,, 1962, Experiments on the scour resistance of cohesive sediments: Jour. Geo phys. Review, v. 67, p. 1437-1446. Morlson, J. R. and Crooke, R. C., 1953, The mechanics of deep water, shallow water, and breaking waves: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 40, 14 p. Morris, G. W.t 1966, Polynomial smoothing, differentiation, and integration by least squares: Pacific Missile Range Tech. Note 3280-17. Munk, W. H., 1949, The solitary wave and its application to surf problems: New York Acad. Sci. Annals, v. 51, p. 376-401. Murray, S. P., 1966, Effects of particle size and wave state on grain dispersion: Univ. Chicago, Fluid Dynamics and Sediment Transport Lab., Tech. Rept. 7, 56 p. ______ , 1967, Control of grain dispersion by particle size and wave state: Jour. Geology, v. 75, p. 612-634. ______ , 1970, Settling velocities and vertical diffusion of particles in turbulent water: Jour. Geophys. Re view, v. 75, p. 1647-1654. Nagata, Y., 1961, Balance of the transport of sediment due to wave action in shoaling water, surf zone and on foreshore: Rees. Oceanog. Works Japan, v. 6, p. 53- 62. ______ , 1964, Deformation of temporal pattern of orbital wave velocity and sediment transport in shoaling water, in breaker zone and on foreshore: Oceanog. Soc. Japan Jour., v. 20, p. 57-70. 0!Brien, M. P. and Rindlaub, B. D., 1934, The transporta tion of bed-load by streams: Am. Geophys, Union Trans., v. 115, p. 593-598. Otto, G. H., 1938, The sedimentation unit and its uses in field sampling: Jour. Geology, v. 46, p. 569-582. Otto, T., 1911, Der Dars und Zingst: Geogr. Gesellsch, Griefswald Jahresberight, v. 13, p. 235-485. 229 Otvos, E. G., 1965> Sedimentation-eroslon cjrcles of single tidal period on Long Island Sound beaches: Jour. Sed. Petrology, v. 35, P* 604-609. Page, R. W., 1963, Geology and ground water appraisal of the naval air missile test center, Point Mugu, Cali fornia: U. S. Geol. Survey Water Supply Paper, 1619-S, 40 p. Palmer, H. D. , 1970, Wave-induced scour around natural and artificial objects: Univ. Southern California, unpubl. dissertation, 172 p. Petterson, H., 1934, Scattering and extinction of light in sea water: Oceanog. Inst. Goteberg Medd., v. 9, p. 1-16. Postma, H., 1967, Sediment transport and sedimentation in the estuarine environment: in Lauff, G. H., Estuaries: Am. Assoc. Adv. Sci. Pub., 83, p. 158-179. Powell, R. W., 1955, The use and misuse of hydraulic models: The Port Engineer, July 1955, P* 21-26. Price, W. A., 1969, Variable dispersion and its effects on the movement of tracers on beaches: Proc. Eleventh Conf. Coastal Engineering, Hew York, Am. Soc. Civil Engineers, v. 1, p. 329-334. Putnam, J. A., Munk, W. H. and Traylor, M. A., 1949, The prediction of longshore currents: Am. Geophys. Union Trans., v. 30, p. 337-345. Rayner, J. N., 1967, Correlation between surfaces by spectral methods: in Merriam, D. P. and Cocke, N. C., ed.. Computer applications in the earth sciences: Colloquium on trend analysis: Kansas Geol. Survey Computer Contr. 12, p. 31-37. Rector, R. L., 1954, Laboratory study of equilibrium pro files of beaches: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo., 41, 38 p. Roper, A. T., Schneider, U. R., and Shen, W. H., 1967, Analytical approach to local scour: Proc. Twelfth Internat. Assoc. Hydraulic Research, v. 3, sec. C18, p. 151-161. 230 Rouse, H., 1937* Modern conceptions of the mechanics of turbulence: Am. Soc. Civil Engineers Trans., v. 102, p. 463-543. ______ , 1964, Sediment transport mechanics: Suspension of sediment: A discussion: Am. Soc. Civil Engineers Proc. Jour. Hydraulics Div., HY 1, v. 90, p. 361-363* Sanders, J. E., 1965, Primary sedimentary structures formed by turbidity currents and related resedimenta tion mechanisms: in Middleton, G. V., ed., Primary sedimentary structures and their hydrodynamic inter pretation: Soc. Econ. Paleontologists and Mineral ogists Spec. Pub. 12, p. 192-219. Savage, R. P., 1957» Sand bypassing at Port Hueneme, California: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo., 92, 34 p. ______ , 1962, Laboratory determination of littoral transport rates: Am. Soc. Civil Engineers Proc. Jour. Waterways and Harbor Div., WW2, p. 69-92. Saville, T., 1950, Model studies of sand transport along an infinitely straight beach. A. Geophys. Union Trans., v. 31, p. 555-556. Schiffman, A., 1965, A study of the swash-surf energy system: Univ. Southern California, unpubl. thesis, 60 p. ______ , 1965b, Energy measurements of the swash-surf system: Limnology and Oceanography, v. 10, p. 255- 260. Schoklitsch, A., 1930, Handbuch des Wasserbaues: Vienna, Springer Verlag. Schwartz, M. L., 1967, Littoral zone tidal-cycle sedi mentation: Jour. Sed. Petrology, v. 37, p* 677-683. Scott, T., 1954, Sand movement by waves: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo., 48, 37 P* Scrlpps Institution of Oceanography, 1947, A statistical study of wave conditions at five open sea localities along the California coast: Wave Rept. 68, 33 p. 2311 Shay, E. A. and Johnson, J. W., 1950, Sand studies in two dimensional wave motion: Univ. California, Inst. Engineering Research, ser. 14, issue 5. Shelford, V. E. and Gall, F. W., 1922, A study of light penetration into sea water made with the Kunz photo electric cell with particular reference to the distri bution of plants: Puget Sound Biol. Station Pub. v. 3, P. 141-176. Shen, H. W., Schneider, V. R., and Karaki, S. S., 1966, Mechanics of local scour: Colorado State Univ., Engineering Research Center Rept., CER66HWS22, 55 p. Shepard, P. P., 1942, Further discussion of the term "low and ball": Jour. Geology, v. 50, p. 216-217. _______, 1950, Beach cycles in Southern California: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo., 20, 26 p. _______, 1963, Submarine geology: 2nd ed., Mew York: Harper and Row, 557 p. Shepard, F. P. and Dill, R. F., 1966, Submarine canyons and other sea valleys, Chicago: Rand-McNally, 381 p. Shepard, F. P., Emery, K. 0., and LaFond, E. 0., 1941, Rip currents: a process of geological importance: Jour. Geology, v. 49, p. 337-369. Shepard, F. P. and Inman, D. L., 1951i Nearshore circula tion: Proc. First Conf. on Coastal Engineering: Univ. California Council Wave Research, p. 50-59. Shields, A., 1936, Anwendung der Ahnlichkeitsmechanik und Turbulenzforshun auf die Seschiebebewegung: Preuss. Versuchsanstalt fur Wasserbau and Sciffbau Berlin, Mitteil., heft 26, 26 p. Simons, D. B„, Richardson, E. V., and Nordin, C. F., 1965, Sedimentary structures generated by flow in alluvial channels: in Middleton, G. V., ed., Primary sedi mentary structures and their hydrodynamic interpreta tion: Soc. Econ. Paleontologists and Mineralogists Spec. Pub. 12, p. 34-52. 232 Sonu, 0. J., McCloy, J. M., and McArthur, D. S., 1967, Long shore currents and nearshore topographies: Proc. Tenth Conf. Coastal Engineering, New York, Am. Soc. Civil Engineers, v. 1, p. 525-549. Sonu, C. J. and van Beek, J. L., 1971, Systematic "beach changes on the Outer Banks, North Carolina: Jour. Geology, v. 79, p. 416-425. Stone, R. 0. and Summers, H. J., 1972, Study of sub aqueous and subaerial sand ripples: Univ. Southern California Rept. USC Geol. 72-1, 274 p. Strahler, A. N., 1966, Tidal cycle changes in an equili brium beach, Sandy Hook, New Jersey: Jour. Geology, v. 74, p. 247-268. Terry, R. D., 1951, Suspended sediment study of surf at Huntington Beach, California: Univ. Southern Cali fornia unpub. report in sedimentation, 21 p. Thorton, E. B., 1971, Variation of longshore current across the surf zone: Proc. Twelfth Conf. Coastal Engineering, New York, Am. Soc. Civil Engineers, v. 1, p. 291-308. Timmermans, P. D., 1935, Proeven over den invloed van golven op een strand: Leidse Geol. Meded., v. 6, aft. 3, p. 233-386. Trask, P. D., 1955, Movement of sand around Southern California promontories: U. S. Army Corps Engineers Beach Erosion Board Tech. Memo., 76, 60 p. Tukey, J. W., 1949, The sampling theory of power spectrum estimates: in Applications of autocorrelation analysis to physical problems symposium, Woods Hole NAVEXOS-P- 735, p. 47-67. University of Iowa, 1970, Laboratory investigation of suspended sediment samplers: Hydraulics Lab., Rept, 5. (mimeographed) U. S. Army Corps of Engineers Beach Erosion Board, 1933, Interim report: April 15, 1933. ______ , 1936, Wave tank experiments on sand movement: Beach Erosion Board Bull., v. 1-2. ______ , 1950, Munch-Petersen's littoral drift formula: Beach Erosion Board Bull., v, 4, p. 1-31. 233 U. S. Army Corps of Engineers, Coastal Eng. Research Center, 1966, Shore protection planning and design: Tech. Rept. 4, 3rd ed., 401 p. U. S, Army Corps of Engineers, Los Angeles District, 1952, Appendix I, Coast of California, Carpinteria to Point Mugu, Beach erosion control study: Course Document 29, 83rd Congress, June 6, 1952. U. S. Army Corps of Engineers, Los Angeles District, 1962, Beach Erosion Control Report on Cooperative Study of the coast of Southern California, Point Conception to Mexican Boundary: Second Interim Rept., Appendix 7. U. S. Army Corps of Engineers, Los Angeles District, 1970, Beach Erosion Control Report, cooperative research and data collection program of the coast of Southern California, Cape San Martin to Mexican boundary: Three year report 1967-1969. U. S. Interagency Committee on Water Resources, 1963, Measurements and analysis of sediment loads in streams: Rept. 14, 151 p. Vanoni, V. A., 1941, Some experiments on the transportation of suspended loads: Am. Geophys. Union Trans., 1941, part 3, P* 608-621. _______, 1946, Transportation of suspended sediment by water: Am. Soc. Civil Engineers Trans., v. 3, P- 67- 133. ________ 1963, Sediment transportation mechanics: Sus pension of sediment: Progress report, Task Committee on sedimentation manual: Am. Soc. Civil Engineers Proc., Jour. Hydraulics Div., HY 5, v. 89, p. 45-76. Vernon, J. W., 1966, Shelf sediment transport system: Univ. Southern California, unpub. dissertation, 135 p. Vollbrecht, K., 1954, Uber die natur des sedimentgleichge- wichtes im littoral: Geofisica Pura e Applicata, Milan, v. 28, p. 159-170. tfastler, T. A., 1963, Application of spectral analysis to stream and estuary field surveys: U. S. Dept. Health, Education and Welfare, Publ. Health Service Pub., 999-WP-7, 31 p. 234 Watts, G. M., 1953, Development and field tests of a sampler for suspended sediment in wave action: U. S. Army Corps of Engineers Beach Erosion Board Tech. Memo. 34, 41 p. ______ , 1965» Sediment discharge to the coast as related to shore processes: in Federal Inter-agency Sedimenta tion Conf., 1963 Proc., U. S. Dept. Agriculture, Misc. Put. 970, p. 738-747. ______ , 1954, Field investigation of suspended sediment in the surf zone: Proc. Fourth Conf. Coastal Engineer ing, Univ. California, Council Wave Research, p. 181- 199. Wiegel, R. L., 1953, Waves, tides, currents and teaches: Glossary of terms and list of standard symtols: Univ. California, Council on Wave Research, 113 p. Wells, D. R., 1967, Beach equilibrium and second-order wave theory: Jour. Geophys. Review, v. 72, p. 497- 504. Wells, D. R. and Sorensen, R. M., 1971, Scour around a circular cylinder due to wave action: Proc. Twelfth Conf. Coastal Engineering, New York, Am. Soc. Civil Engineers, v. 2, p. 1263-1280. Williams, A. T., 1971, An analysis of some factors in volved in the depth of disturbance of teach sand by waves: Marine Geology, v. 11, p. 145-158. Wylie, C. R., 1951, Advanced engineering mathematics: New York, McGraw-Hill. Zeigler, J. M. and Tuttle, S. D., 1961, Beach changes based on dally measurements of four Cape Cod beaches: Jour. Geology, v. 69, p. 583-599. Zenkovich, V. P., 1967, Processes of coastal development: New York, Interscience, 738 p. APPENDICES APPENDIX I Onshore and offshore electronics data and schematics. 236 APPEHDIX I Onshore Electronics Clock Control Module In order to have a predetermined sampling interval and periodicity, precisely timed pulses have to he pro vided. This function is furnished hy the clock control module. The schematic (Pig. X ) shows that there are three possible inputs, an externally provided 1 KHz or 10 KHz and an internal 1 KHz provided hy an Accutronics CD-8-5-28-P oscillator Series 100 which has a frequency stability of t 0.025 percent. This oscillator was utiliz ed in the experiment. The 1000 pulses per second can he connected to a Texas Instruments (TI) 4 hit binary counter (SM 7493 K). This consists of 4 master-slave flip-flops which are internally connected to provide a divide hy 2 counter. Thus there is an output choice of 500, 250, 125 or 62.5 cycles per second. The first one was used. One part of the 500 cycles goes through a TI SN 7400 H, a positive liand gate. This device is a combina tion of an and gate where both inputs have to be positive or logical 1 to get a positive output and a not circuit which reverses the polarity from positive to negative or from a logical 1 to 0 and vise versa. Therefore, a posi- 237 C L O C K C O N T R O L M O D U L E V O L T A C E R E G U L A T O R AN D D - A C O N V E R T E R M O D U L E lapil l»4 Oil* ' l l w y C M t « i D I S P L A Y C O N T R O L M O D U L E M M l* V b u a l O p e r a tio n a l J M p lifi.tr I- uW AIN P L I F M O D U L E l i c v r r t c i H ALL* V C ue: O p a r a tli 238 89 239 tive pulse will go through in every case unless hoth in puts are positive. The TI SN 74121 N, one shot mono stable vibrator because of the added 14 K resistor reduces each input pulse length to 100 microseconds. This 100 microsecond low pulse goes to another circuit in the same nand gate and then exits to the clock: line driver on the amplification module and to the magnetic tape. This 100 microsecond pulse also drives two TI SN 7493 N binary counters. For every negative going pulse the binary coded decimal count increases by one. In the first pulse A goes high and stays high till the next pulse. Then it goes low and B goes high and stays high. With the third pulse A goes high. At the fourth pulse A goes low, B goes low, and C goes high and so forth. This count goes on till at the 63rd millisecond when all 6 binary outputs are high. These binary coded decimal outputs go to the digital to analogue convertor where they become the staircase which Is recorded. At the same time the binary outputs go through a TI SN 7404 N hex invertor which changes their polarity and a TI SN 7430 N an eight input nand gate which lets all the pulses go through till the 64th one. At the 64th pulse all the binary outputs are low. Then, after passing through the hex Invertor these low binary counts are high which inhibits the 8 input nand gate. Its output then stays low. This forces the output pin (#8) of the SN 7400 240 N nand gate to stay high (no more 100 micro second pulses) as is the second pin of the same nand gate. The first gate to which the second gate is coupled is also in the high state till after the 500 Hz has gone through two TI SN 7490 N decade counters. Each of these sends out a pulse for every ten coming in. Therefore, only 5 Hz are extant. The length of the pulse is reduced to 200 microseconds by the SN 74121 N multivibrator. Thus every one-fifth of a second a 200 microsecond negative pulse comes out. When this happens the SN 7400 N nand gate is no longer Inhibited since both inputs (1 and 2) are no longer positive. After 200 microseconds the whole cycle of binary counts is repeated. So for every one-fifth of a second 64 100 microsecond pulses are sent to the line driver and tape recorder and a six bit binary coded decimal to the analogue convertor. After a 200 microsecond pulse the whole cycle starts again Logarithmic Amplifier and Line Driver Module The TI SN 75110 N dual line driver which receives the 100 microsecond pulses is Intended for high speed data communications over long transmission lines. It does this by changing the differences in input voltages to a constant 12 milliamp output current that is switched between the two output terminals. These clock currents are transmitted to the almometer. The -5 volts needed by the line driver Is 241 provided by a 211 2905 transistor coupled to l/2 of a Signetics N 5558 V operational amplifier. On this same module the data from the sensors is amplified either linearly or logarithmically from ± 2.2 to +5 volts. This is done by 1 l/2 Signetics N 5558 V oper ational amplifiers and a IK and 10K Bourns 3059 P trimming potentiometers. The settings for these variable resistors will be discussed under the heading of the display selector module. On each module there are two sets of operational amplifiers, trim pots and a dual line driver so that two almometers can be sampled. Three modules are in place so that a potential exists for sampling six instru ments. Digital to Analogue Convertor and t 15 volt Power Supply Module This module provides the onshore plus and minus 15 volts by means of a Silicon General SG 2501 D dual voltage regulator and two transistors 2N489 and 2N2197. This powers the digital to analogue convertors besides the operational amplifiers. The D/A convertor changes the binary addresses generated by the binary counters on the clock control module to their decimal equivalents. This forms a staircase which is recorded and also monitored. A stairosise is needed on the recorder for it provides a reference to which of the 64 photoelectric cells in each 242 almometer Is "being sampled. Both, the staircase and the photoelectric cells are aotivated "by the same clock pulses. Each of the 64 100 microsecond pulses advanced the voltage plateau of the staircase a little and the photoelectric cells by one. Thus although the photoelectric cell data is in analogue form and is recorded as a continuous curve, each cell's output can be determined by its Juxtaposition to its voltage plateau on the staircase. Display Selector The display selector module provides the important function of enabling the linear data coming in from any one of the almometers to be displayed on an oscilloscope and allowing real time changes in logarithmic amplifica tion of that data. Hence optimal records can be garnered from different environments. If the volume of suspended sediments is low the 1 k trim pot can be set low, if high the setting can be raised to maximize the resolution. The table (p. 246) shows the counting dial settings to achieve these results. The actual setting used was 0.3 volts input equals 0 volts output. This is lessened the higher the Incoming voltages. This setting was used so that water and water with few suspensates would not show hut greater resolution is afforded the heavy suspendeds and bedload quantities of sediment. Offshore Electronics To the almometer in the water goes an 8 lead cable for 2 clock pulses, + 20v, -20v, +10v, + signal and - signal (ground). Since the length and gauge of cable can vary the voltage drop must be treated as an unknown. The nominal ± 20 volts is stabilized at t 15 volts by a Silicon General 2501 D dual tracking regulator. The nominal + 10 volts to a +5 needed for all the integrated circuits except the operational amplifier by a Fairchild pA 725 regulator. The -5 volts for the line receiver is provided by a MPS 6534- transistor and l/2 of the opera tional amplifier N 558V. Clock Decoding and Address Logic The dual line receiver TI SN 75107 N receives the clock input currents. It detects any signal greater than 25 millivolt in amplitude and converts the polarity of the signal to the appropriate 3*5 volt output logic levels. Also its great sensitivity (3 millivolts) allows the pulses to be accurately detected even after deteriora tion in long transmission lines. The incoming pulse is split. One lead goes to two TI SN 74-93 N binary counters. These count till 64, then stop for they are equipped with 244 automatic reset inputs. If both inputs 2 and 3 (see Fig. I E ) are at logical 1 or high, the count stops. The input to gate 2 is provided by the 100 microsecond pulses and 200 microsecond reset pulse directly from the line receiver. These same pulses trigger two TI SN 74121 N one shots. The first of these provides a 150 micro second pulse. The second, since there are no external resistors, a positive 30 nano second pulse which is triggered when the incoming 150 microsecond pulse goes negative. This 30 nano second pulse forms the input to pin #3. It can be seen that only when the 200 micro second reset pulse is in progress will both pins 2 and 3 be positive for 30 nannoseconds. This stops the count and resets the binary counter bach to zero. The least significant output bits (2°, 21, 22) from this binary counter form the addresses to the eight cells in each circuit board. The three most significant bits (2^, 24, 25) go to the 4-llne-to-10-line BOD to decimal decoder (TI SN 7442 N). This integrated circuit consists of 8 invertors and 10 four input nand gates. When the first 8 pulses come in the first circuit board is output enabled (OE). That is, the data can be transmitted while for the other 7 circuit boards the data is blocked. This is possible for each circuit board is equipped with a 2N3706 transistor which inverts the OE signal and a Siliconix 8 channel MO switch with decode driver (SI 3705- h SICK W ICS H 555B V D u a l o p e r a t i o n a l A m p lif ie r 12 11 10 J 9 13 & 7 14 5 15 16 2 o r 4 1 # 0 S i l i c o n i x # 1 51 3705 193 X *2 KOS S w itc h # 9 #4 #5 2 2 N 4.7X 2N3706 Q utpu Enable 2 2 r t >cpcpcpcpcpcpcp- - Io o a _ * 0 0 1 _ * 0 0 1 _ . I ™ ” * 0 0 1 * ooiJ *ooi . o < m — I — _! _=c_I _m _I _=c_I _=c_1 _m_\_=r C lo c k Y C lo c k t 2 7 .4K O u tp u t E n a b le * A d d re ia MdrtM 7 5 4 3 SILICON GENERAL SG2501D D u a l T r a c k in g R e g u la to r a 10 9 12 1 TEXAS INSTALMENTS SK 7493 B in a r y c o u n t e r 5 10 X 15 9 7 6 5 4 3 2 TEXAS INSTRUMENTS 1 SN 7442 K 14 9 TEXAS INSTRUMENTS SN 7493 N ” 2 B in a ry c o u n ta r 1 o f 10 D e c o d e r 1 6 « 0 1 p f 21.5K MOTOROLA HJE 3055 .O L yf 2 3 4 13 rAIACIIXLO UA 733 R e g u la to r 5 7 5 6 TEXAS INSTRUMENTS A 14 11 10 s TEXAS INSTRUMENTS SN 74121 « 0 One S h o t 150 m ic ro a e c 3 7 4 TEXAS INSTRU M EN TS SH 74121 N 0 ^ One S h o t 3 0 n a n o a e c 5N 75107 N U L in e R e c e iv e r I 12 2 11 HPS 6 534 H SIGNET!CS H 555S V th ia l O p e r a t i o n a l A m p lif ie r 2.1S K 4 .9 9 K fO - p - V J 1 246 193K). If the output enable pin (l) is at logical 0, the whole switch is turned off. Thus for each change in the most significant hits a different circuit board can trans mit Its data while the faster changing least significant address bits sample each of the photocells on that board. Hence the output voltage of each of the photocells is sampled sequentially starting at the top of the almometer each one-fifth of a second. Table 1-1. Logarithmic amplification of Input voltage 0 Intercept_________________Zero__________________ Gain 1.0 volt 320 846 0.3 volt 269 728 0.1 volt 214 6l8 0.03 volt 154 497 0.01 volt 103 395 0.003 volt 056 292 APPENDIX II Bathymetric changes and net influx or erosion between Port Hueneme and Point Mugu (from U. S. Army Corps of Engineers, Los Angeles District Hydrographic Surveys D.O. Sheets 3348-3350 C. 2434-2437, D. 2466-2471, E. 2411-2414, D. 2466-2471-70, and field log books). 247 248 EXPLANATION POE TABLES Traverse 1966 Baseline Distance from 6E 1281 + 57.52 ft. 18290 ft. E 8E 1291 + 60.72 ft. 17286 ft. E 10E 1305 + 26.00 ft. 15921 ft. E 14E 1350 + 84,00 ft. 11363 ft. E 16E 1371 + 50.00 ft. .. 9297 ft. E 18E 1391 + 12.00 ft. 7335 ft. E 20E 1411 + 32.04 ft. 5315 ft. E 22E 1434 + 28.00 ft. 3019. ft. E 22EX 1464 + 47.00 ft. 0 23E 1481 + 61.00 ft. 1714 ft. ff 23E5 1506 + 14.00 ft. 4167 ft. W 24E 1537 + 60.00 ft. 7313 ft. W 24E10 1550 + 25.00 ft. 8678 ft. w 25E 1574 + 11.00 ft. 10964 ft. w -2 ^ 5 1606 + 57.. 00 ft. 14210 ft. w 24$ September-October 1938 Posi tion Tra verse MLLW Dist. -12 Dist. -24 Dist. 6E 320 845 1730 8E 383 745 1770 10E 933 1230 2370 14E 1400 1800 2490 16E 920 1365 1890 18E 745 1165 1645 20E 645 1035 1505 22E 510 865 1485 22E, - - 23E 605 965 1600 23E. - - - - 24E 620 1120 1960 24E10 - - 25E 850 1230 1705 25E15 - 4 * - 250 July-August 1948 Posi tion MLLW -12 -24 -30 Tra verse Dist. Change Dist.' Change Dist. Change Dist, Change 6E 315 - 11.7 630 -102.5 1860 +225.9 8E 320 - 84.8 550 -101.1 1670 - 9.4 10E 625 -440.3 1040 -184.9 2490 +376.6 14E 735 -189.4 1190 -241.6 2095 + 63.5 16E 595 -789.3 950 -484.3 1720 +198.2 18E 395 -112.6 880 -122.4 1665 +227.1 20E 515 - 85.5 815 - 99.2 1475 +120.7 1945 22E 290 -276.1 730 - 8.4 1430 - 6.1 22E! - - - - - - - 23E 295 -338.4 805 - 47.1 1460 -386.2 23B5 - - - - - - - 2AE 385 -165.3 935 -187.2 1670 - 67.2 24E10 - - - - - - - 25E 690 1015 1690 25E15 - - - - - - Total, (x 10 cu. yds .) -2493.4 -1578.7 +1515.5 251 September 1953 Posi tion MLLW -12 -24 30 Tra verse Dist. Change Dist. Change Dist. Change Dist. Change 6E - - - - - - - - 8E - - - - - - - - 10E 440 -148.0 1050 +935.5 1850 -729.4 2400 + 8.6 14E 690 + 7,6 1085 - 26.5 1485 -127,5 1875 - 55.7 16E 500 + 11.6 920 - 20.3 1285 -112.5 1825 -106.1 I8E 420 + 9.3 890 - 15.8 1215 -117.5 1815 -207.6 20E 400 -134.6 885 +104.6 1205 + 41.7 1705 -126.9 22E 255 + 33.9 910 + 45.2 1480 + 41.2 2085 -146.2 22Et 385 + 5.8 780 - 41.8 1225 - 17.6 1610 -138.6 23E 75 - 16.7 710 - 1.0 1430 +117.6 2065 - 43.3 23EC 244 - 5.3 755 + 5.6 1625 -120.9 2280 + 15.4 24E 215 - 6.4 860 -110.8 1305 - 62.5 1975 - 15.9 24EiO 270 - 67.3 460 -431.6 1340 - 36.9 1930 -163.4 25E 135 - 60.1 475 -280.4 1175 - 98.9 1650 - 41.5 25E15 195 - 690 - 1320 - 1910 - Total. ( X 104 cu, yds .) -370.2 +162.7 -1223.2 -1021.2 252 June 1959 Posi tion MLLW -12 -24 30 Tra verse Dist. Change Dist. Change Dist. Change Dist. Change 6E NA - 530 - 1440 +626.7 2330 8E 180 - 25.0 565 - 18.6 1610 + 60.8 2330 10E 150 - 30.7 380 -221,3 1620 +1012.6 2170 14E 400 - 73.6 840 -176.8 1840 +247.1 2470 16E 50 -109.0 465 -291.9 1670 +230.6 2275 18E 50 - 64.0 445 -130.0 1390 +109.6 1945 20E 155 - 78.0 390 -134.2 1255 + 33.2 1775 -208,1 22E -10 - 81.1 460 -169.6 1375 -121.9 1900 22EL - - - - - - - - 23E 65 -432.3 605 -342,7 1415 +169.5 2125 23E5 - - - - - - - - 24E 410 -199.1 810 -105.8 1595 -117.7 2160 24E10 - - - - - - - - 25E 555 - 975 - 1550 - 1950 - 25E15 - - - - - - - - Total. (x 104 cu. yds.) -1083.8 -1590.9 +2250.5 253 June-July 1961 Posi tion MLLW -12 -24 30 Tra verse Dist. Change Dist. Change Dist. Change Dist. Change 6E 390 -154.7 750 -619.9 1930 + 62.2 2300 -196.7 • \ 8E 510 +179.7 740 + 91.4 1570 -661.8 2205 + 65.8 10E 610 +425.4 920 +310.1 1600 -1380.2 2250 +131.9 14E 750 +107.1 1125 + 52.8 1910 + 29.6 2540 - 69.3 16E 260 -168.7 560 +150.1 1430 -339.3 1870 +53.0 18E -75 -101,4 315 -102.8 1115 -158.3 1875 +167.1 20E -125 - 81.4 295 - 26.2 1145 - 52.9 1725 -299.4 22E -10 - 28.5 350 -641.7 1280 -2012.7 1780 -1884.3 22El -10 - 470 - 1260 - 1820 - 23E 135 -144.4 530 -467.0 1435 -1619.3 2055 -1691.5 23E, 130 - 580 - 1620 - 2250 - 24E 340 -178.5 1010 -277.5 1560 -948.3 2090 -738.3 24E10 385 - 845 - 1630 - 2145 - 25E 535 - 1020 - 1600 - 2050 - 25E. _ 15 420 - 710 - 1370 - 1810 - Total, (* 104 cu. yds 0 -145.4 -1530.7 -7081.0 -4461.7 June 1962 Posi tion MLLW -12 -24 30 Tra verse Dist. Change Dist. Change Dist. Change Dist. Change 6E 150 - 85.2 675 + 33.7 1835 + 12.5 2330 + 59.1 8E 240 -138.8 630 + 0.4 1555 +117.8 2220 - 69.8 10E 270 -188.5 665 - 65.5 1575 +112.0 2085 -297.0 14E 840 + 21.0 1120 + 23.1 1800 +383.2 2310 - 22.1 X6E 280 + 18.9 670 + 60.0 1480 + 43.5 2120 + 17.2 18E -5 + 27.1 395 + 42.9 1255 + 92.0 1915 - 91.2 20E -35 + 10.0 445 +108.7 1295 + 70.5 1820 - 63.3 22E -80 - 43.2 420 + 40.5 1370 + 10.2 1820 -111.6 22EL -120 - 30.3 400 + 41.4 1180 - 66.3 1690 - 80.2 23E 65 - 18.6 635 + 76.5 1415 + 23.2 1975 -134.9 23E5 120 - 14.5 590 -183.0 1680 +289.9 2220 - 99.7 24E 320 + 3.3 740 - 85.0 1560 +110.2 2090 - 21.9 24Eio 395 + 18.8 825 +236.1 1685 -150.7 2145 -531.8 25E 610 + 22.6 920 - 49.0 1370 -137.1 1710 -197.2 25E15 420 - 770 - 1440 - 1850 - Total, (x 104 -397.5 +280.8 +910.9 -1644.4 255 June-July 1966 Posi tion MLLW -12 -24 30 Tra verse Dist., Change Dist. Change Dist. Change Dist. Change 6E 310 + 51.1 730 + 6.3 1785 - 87.3 2220 - 94.9 8E 350 + 95.6 785 + 59.9 1520 -187.3 2050 - 74.4 10E 580 +165.4 920 + 20.2 1550 -418.2 2080 +149.5 14E 740 + 3.8 1030 + 6.8 1600 -127.6 2235 +273.8 16E 400 + 94.8 785 +140.8 1500 - 89.2 2150 + 77.6 18E 330 +162.9 830 +107.8 1460 -129.1 2180 +181.8 20E 300 + 42.3 600 +174.3 1300 -183.6 1960 +268.0 22E 280 +151.3 700 +259.5 1410 -118.6 2020 +269.3 22EL 320 +118.8 770 + 42.4 1440 - 14.0 1985 + 92.5 23E 330 +113.3 710 - 70.4 1420 -258.3 2050 +112.0 23E5 315 + 74.3 600 - 90.0 1470 -425.9 2090 +115.9 24E 335 - 9.9 710 - 34.4 1360 -158.3 1960 + 30.1 2AE10 290 - 37.5 710 - 18.8 1400 -402.4 1920 -406.7 25E 545 - 40.6 940 - 12.3 1340 - 79.9 2000 +409.3 25E15 350 - 670 - 1340 - 1790 - Total- <x 104 cu* yds.) +1086.6 +592.1 -2679.7 +1403.8 256! May-July 1970 Posi tion MLLW -12 -24 30 Tra verse Dist. Change Dist. Change Dist. Change Dist. Change 6E 300 - 2.6 740 - 8.8 1560 -127.0 2020 + 0.2 8E 380 + 20.4 730 - 5.3 1400 - 4.5 1940 - 34.8 10E 640 + 39.0 1015 +126.3 1690 + 34.1 2150 -241.5 14E 740 + 2.0 1130 + 96.9 1625 -167.2 2110 -123.0 16E 430 + 26.2 920 + 62.6 1370 -260.6 1980 -115.6 18E 425 + 37.1 910 +134.9 1320 -280.5 1970 - 56.5 20E 360 +147.5 880 +138.3 1280 -323.7 1960 - 30.1 22E 260 + 56.5 980 +167.2 1380 -320.7 1940 - 66.9 22E1 270 - 34.9 850 + 74.6 1370 -100.2 1920 + 18.2 23E 165 - 60.6 740 +162.8 1380 - 67.6 2025 +103.7 23E5 230 - 68.4 760 +290.1 1550 + 0.5 2235 +134.7 24E 240 - 15.6 855 +102.4 1485 + 44.5 2100 + 76.7 24Eio 290 - 32.1 850 +151.4 1590 +237.5 2210 + 32.0 25E 400 -109.7 1020 +155.9 1625 +204.1 2150 - 45.9 25E1S 130 - 660 - 1300 1810 - Total + 4.8 +1649.3 -1131.3 -348.8 25.7 March 1971 Posi tion MLLW -12 -24 30 Tra verse Dist. Change Dist. Change Dist. Change Dist, Change 6E - * * - - * • - - - 8E - - - - - - - - 10E 440 -148.0 1050 4935.5 1850 -729.4 2400 + 8.6 14E 690 + 7.6 1085 - 26.5 1485 -127.5 1875 - 55.7 16E 500 + 11.6 920 - 20.3 1285 -112.5 1825 -106.1 18E 420 + 9.3 890 - 15.8 1215 -117.5 1815 -207.6 20E 400 -134,6 885 +104.6 1205 + 41.7 1705 -126.9 22E 255 + 33.9 910 + 45.2 1480 + 41.2 2085 -146.2 22El 385 + 5.8 780 - 41.8 1225 - 17.6 1610 -138.6 23E 75 - 16.7 710 - 1.0 1430 +117.6 2065 - 43.3 23E5 244 - 5.3 755 + 5.6 1625 -120.9 2280 + 15.4 24E 215 - 6.4 860 -110.8 1305 - 62.5 1975 - 15.9 24E10 270 - 67.3 460 -431.6 1340 - 36.9 1930 -163.4 25E 135 - 60.1 475 -280.4 1175 - 98.9 1650 - 41.5 25E15 195 Total, (x 10 cu. yds.) -370.2 690 +162.7 1320 -1223.2 1910 -1021.2 APPENDIX III Bathymetric changes and cut and fill values for U. S. Army Corps of Engineers (1970) traverses for 1938 to 1971* This informa tion was used to evaluate the long-term behavior of sediments on the inner shelf between Ventura and Point Mugu. 258 259 July-August 1948 Posi tion MLLW -12 -24 ______-30 Tra- verse Dist, Change Dist, Change Dist. Change Dist, Change 6E 315 - 11.7 630 -102.5 1860 +225.9 8E 320 - 84.8 550 -101.1 1670 - 9.4 10E 625 -440.3 1040 -184.9 2490 +376.6 14E 735 -189.4 1190 -241.6 2095 + 63.5 16E 595 -789.3 950 -484.3 1720 +198.2 18E 395 -112.6 880 -122,4 1665 +227.1 20E 515 - 85.5 815 - 99.2 1475 +120.7 22E 290 -276.1 730 - 8.4 1430 - 6.1 22E± - - - - - - 23E 295 -338.4 805 - 47.1 1460 -386.2 23E5 - - - - - 24E 385 -165.3 935 -187.2 1670 - 67.2 24E10 - - - - - 25E 690 1015 1690 25E15 - - - - - Total (xlO* cu. yds,.) -2493.4 -1578.7 +1515,5 260 September 1953 Posi tion MLLW -12 -24 ______-30 Tra- verse Dist. Change Dist* Change Dist. Change Dist. Change 6E 145 - 33.4 730 + 97.4 1905 -750.2 8E 290 -124.3 680 - 86.1 1680 -311.3 10E 150 -399.1 380 -249.7 1515 -761.0 14E 485 - 94.7 1190 - 6.7 1900 - 93.7 16E 350 -103.4 710 - 97.2 1615 - 27.8 18E 125 -107.7 640 - 99.7 1415 - 49.7 20E 335 - 92.9 610 - 55.5 1350 +109.9 1865 22E 105 - 83.2 655 -119.2 1515 -426.0 2080 22EX - - - - - - - 23E 190 670 1525 23E5 - - - - - - 24E NA 24E10 25E NA m - - * 25E. . Total, (x 10 cu, yds. ) -1038.7 -616.7 -1457.8 261 June 1959 Posi tion MLLW -12 -24 ______-30 Tra- verse Dist, Change Dist, Change Dist. Change Dist. Change 6E NA 530 - 1440 +626,7 2330 8E 180 - 25.0 565 - 18.6 1610 + 60.8 2330 10E 150 - 30.7 380 -221.3 1620 +1012.6 2170 14E 400 - 73.6 840 -176.8 1840 +247.1 2470 16E 50 -109.0 465 -291.9 1670 +230.6 2275 18E 50 - 64.0 445 -130,0 1390 +109.6 1945 20E 155 - 78.0 390 -134.2 1255 + 33.2 1775 22E -10 - 81,1 460 -169.6 1375 -121.9 1900 22El - - - - - - 23E 65 -432.3 605 -342.7 1415 +169.5 2125 23E5 - - * » - - - 24E 410 -199.1 810 -105.8 1595 -117.7 2160 2*E10 - m - m - - - 25E 555 * * 975 - 1550 1950 25E15 - - - - - - Total, (x 10* cu. yds.) -1083.8 -1590.9 +2250.5 262 June-July 1961 Posi tion MLLW -12 -24 -30 Tra- verse Dist. Change Dist. Change Dist. Change Dist. Change 6E 390 -154.7 750 -619.9 1930 + 62.2 2300 -196.7 8E 510 +179.7 740 + 91.4 1570 -661.8 2205 + 65.8 10E 610 +425.4 920 +310.1 1600 -1380.2 2250 +131.9 14E 750 +107.1 1125 + 52.8 1910 + 29.6 2540 - 69.3 16E 260 -168.7 560 +150.1 1430 -339.3 1870 + 53.0 18E -75 -101.4 315 -102.8 1115 -158.3 1875 +167.1 20E -125 - 81.4 295 - 26.2 1145 - 52.9 1725 -299.4 22E o H t - 28.5 350 -641.7 1280 -2012.7 1780 -1884.3 22EL -10 - 470 1260 - 1820 - 23E 135 -144.4 530 -467.0 1435 -1619.3 2055 -1691.5 23E5 130 - 580 - 1620 - 2250 - 24E 340 -178.5 1010 -277.5 1560 -948.3 2090 -738.3 24E10 385 - 845 - 1630 - 2145 - 25E 535 - 1020 1600 - 2050 - 25E10 420 - 710 - 1370 - 1810 - Total, (x 10* cu* yds .) -145.4 -1530.7 -7081.0 -4461.7 26j June 1962 Posi tion MLLW -12 -24 -30 Tra verse Dist,, Change Dist. Change Dist. Change Dist. Change 6E 150 - 85.2 675 + 33.7 1835 + 12.5 2330 + 59.1 8E 240 -138.8 630 + 9.4 1555 +117,8 2220 - 69.8 10E 270 -188.5 665 * * 65.5 1575 +112.0 2085 -297.0 14E 840 + 21.0 1120 + 23.1 1800 +383.2 2310 - 22.1 16E 280 + 18.9 670 + 60.0 1480 + 43.5 2120 + 17.2 18E - 5 + 27.1 395 + 42.9 1255 + 92.0 1915 - 91.2 20E -35 + 10.0 445 +108.7 1295 + 70.5 1820 - 63.3 22E -80 - 43.2 420 + 40.5 1370 + 10. 2 1820 -111.6 22El -120 - 30.3 400 + 41.4 1180 - 66.3 1690 - 80.2 23E 65 - 18.6 635 + 76.5 1415 + 23.2 1975 -134.9 23E5 120 - 14.5 590 -183.0 1680 +289.9 2220 - 99.7 24E 320 + 3.3 740 - 85.0 1560 +110.2 2090 - 21.9 24E10 395 + 18.8 825 +236.1 1685 -150.7 2145 -531.8 25E 610 + 22.6 920 - 49.0 1370 -137.1 1710 -197.2 25Ei5 420 - 770 - 1440 1850 - Total -397.5 +280.8 +910.9 -1644.4 2 64 Posi tion MLLW Tra verse Dist. Change 6E 310 + 51.1 8E 350 + 95.6 10E 580 +165.4 14E 740 + 3.8 16E 400 + 94.8 18E 330 +162.9 20E 300 + 42.3 22E 280 +151.3 22EL 320 +118.8 23E 330 +113.3 23E5 315 + 74.3 24E 335 - 9.9 24E10 290 - 37.5 25E 545 - 40.6 25E15 350 - Total, +1086*6 (x 104 cu. yds.) June-July 1966 -12 Dist. Change Dist. 730 + 6.3 1785 785 + 59.9 1520 920 + 20.2 1550 1030 + 6.8 1600 785 +140.8 1500 830 +107,8 1460 600 +174.3 1300 700 +259.5 1410 770 + 42.4 1440 710 - 70.4 1420 600 - 90.0 1470 710 - 34.4 1360 710 - 18.8 1400 940 - 12.3 1340 670 1340 +592.1 24 -30 Change Dist. Change - 87.3 2220 - 94.9 -187.3 2050 - 74.4 -418.2 2080 +149,5 -127.6 2235 +273.8 - 89.2 2150 + 77.6 -129.1 2180 +181.8 -183,6 1960 +268.0 -118.6 2020 +269.3 i 4. 0 1985 + 92.5 -258.3 2050 +112,0 -425.9 2090 +115.9 -158.3 1960 + 30.1 -402.4 1920 -406.7 - 79.9 2000 +409.3 1790 - 2679.7 +1403.8 26g Mav-Julv 1970 Posi tion MLLW -12 -24 -30 Tra verse Dist. Change Dist. Change Dist. Change Dist. Change 6E 300 - 2.6 740 - 8.8 1560 -127.0 2020 + 0.2 8E 380 + 20.4 730 - 5.3 1400 - 4.5 1940 - 34.8 10E 640 + 39.0 1015 +126.3 1690 + 34.1 2150 -241.5 14E 740 + 2.0 1130 + 96.9 1625 -167.2 2110 -123.0 16E 430 + 26.2 920 + 62.6 1370 -260.6 1980 -115.6 18E 425 + 37.1 910 +134.9 1320 -280.5 1970 - 56.5 20E 360 +147.5 880 +138.3 1280 -323.7 1960 - 30.1 22E 260 + 56.5 980 +167.2 1380 -320.7 1940 - 66.9 22Ej 270 - 34.9 850 + 74.6 1370 -100.2 1920 + 18.2 23E 165 - 60.6 740 +162,8 1380 - 67.6 2025 +103.7 23E5 230 - 68.4 760 +290.1 1550 + 0.5 2235 +134.7 24E 240 - 15.6 855 +102,4 1485 + 44.5 2100 + 76.7 2kh o 290 - 32.1 850 +151.4 1590 +237.5 2210 + 32.0 25E 400 -109.7 1020 +155.9 1625 +204.1 2150 - 45.9 25E15 130 - 660 - 1300 - 1810 m Total, (x 10 cu. yds.) + 4.8 +1649.3 -1131.3 -348.8 266 March 1971 Posi tion MLLW -12 -24 -30 Tra verse Dist,, Change Dist. Change Dist. Change Dist. Change 6E - - - - - - - 8E - - - - - - - a t 10E 440 -148.0 1050 +935.5 1850 -729.4 2400 + 8.6 14E 690 + 7.6 1085 - 26.5 1485 -127.5 1875 - 55.7 16E 500 + 11.6 920 - 20.3 1285 -112.5 1825 -106.1 18E 420 + 9.3 890 - 15.8 1215 -117.5 1815 -207.6 20E 400 -134.6 885 +104.6 1205 + 41.7 1705 -126.9 22E 255 + 33.9 910 + 45.2 1480 + 41.2 2085 -146.2 22EX 385 + 5.8 780 - 41.8 1225 - 17.6 1610 -138.6 23E 75 - 16.7 710 - 1.0 1430 +117.6 2065 - 43.3 23E5 244 - 5.3 755 + 5.6 1625 -120.9 2280 + 15.4 24E 215 - 6.4 860 -110.8 1305 - 62.5 1975 - 15.9 24E10 270 - 67.3 460 -431.6 1340 - 36.9 1930 -163.4 25E 135 - 60.1 475 -280.4 1175 - 98.9 1650 - 41.5 25E.R 195 15 Total, <x 10 cu* yds*) -370.2 690 +162.7 1320 -1223.2 1910 -¥021.2 .APPENDIX IV Mean sand diameter ranked according to tidal stage. 267 269 Table 1-2. Mean sand diameter ranked according to tidal stage Falling tide_________ Rising tide__________ Mean Mean Distance Diameter Rank Distance Diameter Rank 130 .191 56 130 .189 55 120 .186 53 120 .176 49 140 .174 47.5 150 .173 46 150 .172 45 140 .169 43.5 140 .169 43.5 250 .168 42 170 .165 39.5 125 .162 38 140 .161 36,5 190 .160 34 160 .160 34 135 .158 31 140 .154 27 135 .153 26 210 .152 25 165 .145 19 270 .142 17 160 .141 16 175 .138 13 180 .135 11 200 .134 9.5 220 .133 8 220 .128 7 325 .126 6 220 .124 5 270 .119 3 210 .118 1.5 195 .118 1.5 110 .230 62 130 .209 61 125 .201 60 120 .199 59 110 .198 58 110 .197 57 130 .186 53 140 .186 53 135 .180 51 165 .178 50 190 .174 47.5 170 .166 41 190 .165 39.5 135 .161 36.5 210 .160 34 120 .159 32 235 .157 30 160 .156 29 270 .155 28 175 .150 24 240 .149 23 180 .148 21 230 .148 21 270 .148 21 190 .144 18 375 .139 15 200 .138 13 205 .138 13 325 .134 9.5 240 .123 4 R = 1068 R = 885 APPENDIX V 270 DERIVATION OP FORMULAS The derivation of formulas to smooth data fcy a second degree polynomial using least squares is as follows. Let Si be the observed value at point 1. This may be range, azimuth, elevation, range rate or any function which may vary with time. Let Si fp be the corresponding values on the curve „ = b0 + bit + bgt2, which is fitted by least squares*to p data points to obtain the un known coefficients b0, bi» and bg. Proceeding by least squares theory, the quantity to minimize This may be accomplished by setting the partial derivatives of Y with respect to b0, bi» and bg equal to zero. Thus is X CS; (l) (2) 2T1 where all summations are taken from i = -K to +K. Then the normal equations become X. * + £ t r : + = S.S.- 4 - t , 3 i i * = - S ! S ; t i Vi„ -V L ,2"t-,,4- (3) Now without the loss of generality, the data may be con- sidered as centered about the time point t = 0, since t does not enter into the calculations. Now if the data are taken at equal time intervals, T, then t]_ = iT. If 1 is the index which is summed over p points centered about zero, from -K to K, then S. = O Equations (3) become s.*; 1 - £VC + I = P (4) t-k ’ x ' V^TSL*- ^ 21^ (5) (6) 272 Now we solve from the above set for b0» b^, and b2; from (5), where «S “ * “ W Q ~ G7 L - -U. V> = _ S.L Si T * ^ ” <7> Prom (4) and (6) By substituting (8) into (6) we obtain , W^SSi. - WlSLlSi — 5----------- (9) MoW, - Hi Then for smoothing, sv = k . + k - T + t ^ n . i v f e - + (10) J. ]Qt i ^ W- U.>L-U^ )^L APPENDIX VI Poll wave photograph. Figure shows a roll wave or hydraulic jump in the transition zone of the test area. 273 274

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Early Diagenesis In Southern California Continental Borderland Sediments

PDF

Wave-Induced Scour Around Natural And Artificial Objects

PDF

The Aleutian-Kamchatka Trench Convergence: An Investigation Of Lithospheric Plate Interaction In The Light Of Modern Geotectonic Theory

PDF

Late-Neogene Paleomagnetic And Planktonic Zonation, Southeast Indian Ocean - Tasman Basin

PDF

Petrology And Depositional History Of Late-Precambrian - Cambrian Quartzites In The Eastern Mojave Desert, Southeastern California

PDF

Marine Geology Of The Baja California Continental Borderland, Mexico

PDF

Oceanography And Late-Quaternary Planktonic Foraminifera, Southwestern Indian Ocean

PDF

Sedimentology And Pleistocene History Of Lake Tahoe, California - Nevada

PDF

Distribution And Transport Of Suspended Matter, Santa Barbara Channel, California

PDF

Holocene sedimentation in the southern Gulf of California and its climatic implications

PDF

Ecology And Paleoecology Of Hudson Bay Foraminifera

PDF

Evolutionary paleoecology and taphonomy of the earliest animals: Evidence from the Neoproterozoic and Cambrian of southwest China

PDF

Recent And Upper Pleistocene Sediments Of The Southwestern Portion Of Losangeles County, California

PDF

Continental Slopes Of The World

PDF

Distribution Of Foraminifera And Radiolaria In Sediments Of The Scotia Sea Area, Antarctic Ocean

PDF

Shelf Sediment Transport System

PDF

Marine Geology Of The Andaman Basin, Northeastern Indian Ocean

PDF

Ultrastructure Of Tests Of Some Recent Benthic Hyaline Foraminifera

PDF

Economic Analysis Of Factors Underlying Pricing In The Southern California Tuna Canning Industry

PDF

Heat Flow And Other Geophysical Studies In The Southern California Borderland

Asset Metadata

Creator Brenninkmeyer, Benno Max (author)

Core Title Synoptic Surf Zone Sedimentation Patterns

Degree Doctor of Philosophy

Degree Program Geological Sciences

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

Tag Geology,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Gorsline, Donn S. (committee chair), Osborne, Robert H. (committee member), Tibby, Richard B. (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c18-861283

Unique identifier UC11364206

Identifier 7331633.pdf (filename),usctheses-c18-861283 (legacy record id)

Legacy Identifier 7331633

Dmrecord 861283

Document Type Dissertation

Rights Brenninkmeyer, Benno Max

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 au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA