ONSHORE-OFFSHORE SAND TRANSPORT ON DEL MONTE BEACH, CALIFORNIA John David Wi 1 1 iamson NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS ONSHORE-OFFSHORE SAND TRANSPORT ON DEL MONTE BEACH by , CALIFORNIA John David Williamson The sis Advisor: Warren C. Thompson September 1972 Approved {fin. pabtic n.oXojxML; dU-tAxhuution. untimltzd. T149564 Onshore-Offshore Sand Transport on Del Monte Beach, California by John David Williamson Ensign, United States Navy B.S., University of Oklahoma, 1971 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN OCEANOGRAPHY from the NAVAL POSTGRADUATE SCHOOL September 1972 ABSTRACT Daily sand volume transport values were calculated for a selected beach profile during a two-month period. Wave data were recorded continuously directly seaward of the profile. Tide effects were largely filtered out by use of a lunar day (24.8 hour) sampling interval. Offshore sand transport occurred in isolated events of one to two-day duration, and had a maximum value of 132.5 cubic feet/foot of beach width/lunar day. Onshore transport occurred over longer intervals of up to seven days, and had a maximum value of 47.0 cubic feet/foot/day. Onshore-offshore transport over a 24.8 hour period depends, to a first approximation, on the mean wave steepness incident upon the beach and the initial beach slope for the period. If the initial beach slope is greater (less) than the equili- brium slope associated with the existing wave conditions, or if the profile is initially at equilibrium and the wave steepness increases (decreases) , sand will be moved offshore (onshore). The closer to equilibrium the beach is, the smaller the transports are. TABLE OF CONTENTS I. INTRODUCTION 7 A. OBJECTIVE OF THE STUDY 7 B. DESCRIPTION OF THE BEACH 8 C. FIELD AND OBSERVATIONAL SETUP .14 II. BASIC CONSIDERATIONS 16 III. DATA ANALYSIS 19 A. BEACH DATA 19 1. Computation of Sand Transport 19 2. Computation of Initial Beach Slope ... 20 B. WAVE AND TIDE DATA 24 IV. RESULTS AND INTERPRETATION 30 A. OBSERVED ONSHORE-OFFSHORE SAND TRANSPORTS . 3 0 B. RELATION BETWEEN VOLUME TRANSPORT AND INCIDENT WAVES 32 1. Synoptic Wave Events 35 2. Wave-Beach Correlation 39 C. THE EFFECT OF WAVE POWER AND THE TIDES ... 42 V. CONCLUSIONS 4 3 LIST OF REFERENCES 4 5 APPENDIX A DAILY SAND VOLUME TRANSPORTS 4 7 APPENDIX B WAVE AND TIDE DATA 54 APPENDIX C MEAN BEACH SLOPES 6 2 INITIAL DISTRIBUTION LIST 63 DD FORM 1473 65 3 LIST OF TABLES Table Page 1 Wave and Beach Parameters 34 LIST OF TABLES Table Page 1 Wave and Beach Parameters 34 LIST OF FIGURES Figures Page 1 Monterey Bay, California 9 2 Location of Beach Profile and Wave Gauge . . io 3 Del Monte Beach Profile 11 4 Seaward Portion of Profile and Reference Rail 12 5 Calculation of Sand Transport 21 6 Calculation of Beach Slope 22 7 Daily Sand Transports and Wave and Tide Data 28 8 Cumulative Sand Transports 29 9A-9D Synoptic Wave Events 36-37 10 Daily Sand Transport as a Function of Wave Steepness and Initial Beach Slope 41 ACKNOWLEDGEMENTS The author wishes to express his appreciation and thanks to Professor Warren C. Thompson who suggested the use of synoptic wave graphs in the analysis of the data, and whose many hours of patient assistance were invaluable in the com- pletion of this investigation. The facilities of the W. R. Church Computer Center at the Naval Postgraduate School were utilized for data reduction and analysis. I. INTRODUCTION A. OBJECTIVE OF THE STUDY Previous investigators have demonstrated that natural sand beaches on the open coast are sensitive to incident ocean waves, and that the observable portion of such beaches may change measurably over very short time intervals ranging from less than an hour to approximately one day, (Shepard and LaFond, 1940; Inman and Filloux, 1960; Strahler, 1964; Rohrbough, Koehr, and Thompson, 1964; Ingle, 1966; Harrison, et al., 1968; Haydock, 1969). Such changes in a beach profile are a consequence of onshore-offshore transport of sand by wave action, with the nature of these changes presumably being closely related to the character of the waves incident upon the beach. However , to the author's knowledge, only one quantitative relationship has been published (Thompson and Harlett, 1969) on the response of a natural beach to the incident waves. The present investigation utilizes the beach-profile data gathered by Harlett (1967) in Monterey Bay, California. Whereas Harlett worked with beach profile changes, this study examines sand volume gains and losses. The beach-profile measurements used were made daily over a two-month period along a selected profile, and the waves incident upon the profile were recorded continuously during most of the period. The objectives of this study were: (1) to describe, on a daily basis over the two-month period, the characteristic values of and the variation in the volumes of sand transported on and off the beach in a direction perpendicular to the shore, and (2) to relate this sand transport to the incident wave conditions . B. DESCRIPTION OF THE BEACH The beach profile examined in this study is located on Del Monte Beach in the southern end of Monterey Bay, California (Figures 1-4). Del Monte Beach is a long, unbroken, gently curving, sand beach backed by an inactive dune ridge. The shoreline is in dynamic equilibrium and has remained essen- tially in the same mean location since the earliest survey of 1851 (House Doc. No. 219, 1959). The beach is quite uniform laterally and characteristically possesses a simple profile with no offshore bars. The slope at the mid- tide level is approximately 1:50. Seaward of the surf zone the bottom is smooth and slopes gently seaward with the bottom contours being parallel to the shoreline. The material composing the exposed portion of the beach is a very well sorted, medium to fine, quartz-feldspar sand with a mean grain diameter of about 2$. The textural pro- perties of the sand, sampled daily across the beach face during the period of the field measurements, were found to be nearly constant (Harlett, 1967) . Subdued cusps frequently occurred on the upper portion of the beach during the field study. 8 122°10' 122°00' 121° 50' ?"^"*500.....; MILES 37°00'- 36°50'- 36°40/ DEPTHS IN FATHOMS Figure 1: MONTEREY BAY, CALIFORNIA Figure 2: LOCATION OF BEACH PROFILE AND WAVE GAUGE 10 t* *' *ri A :■; H Pm O Pi CM u < w CQ W Eh Z o s w Q CD M •H Cm 11 u e W U z w w Cm W OS Q Z w hH H Cm O « En O Z o H En Pi O a* a Pi < w CO (L) M •H Cm 12 The beach studied is protected by the Monterey Peninsula in such a manner that essentially all waves arriving on the beach from the open ocean are transformed by intense refraction to swell of low height and steepness (Figure 1) . In addition, refraction is such that the waves arrive on the beach with their crests parallel or nearly parallel to shore. Plunging breakers with heights characteristically below three feet predominate. Because of the very low to zero breaker angles character- istic of waves on Del Monte Beach, littoral drift is negligible The absence of littoral drift is amply demonstrated by the fact that a littoral barrier about 1000 yards downcoast from the profile site has not caused accretion or erosion of the adjacent shoreline, and that the beach at the profile site has remained stable since its construction. The barrier in question is a solid bulkhead built in April 1962, which runs alongside Monterey Municipal Wharf No. 2 from the rear of the beach to a depth of about 18 feet. In view of the absence of littoral drift and the lateral uniformity of the beach, it was concluded that the changes observed in the profile of the beach involve only onshore-offshore transport of sand. The tides in Monterey Bay, as for the entire Pacific Coast, are of the mixed type, and have an average diurnal range of 5.3 feet (MLLW to MHHW) . The tidal datum for the coast is MLLW. 13 It is evident from this description that the beach under investigation is a natural laboratory where profile changes may be examined under relatively simple beach conditions and distinctive wave conditions. Accordingly, it appears that conditions are simple enough to expect that the observed onshore-offshore transport of sand can be correlated with the incident wave conditions. C. FIELD AND OBSERVATIONAL SETUP The beach and wave information utilized in this study were collected over the period from 1 February through 31 March, 1967. Sand-level measurements were made relative to a series of twenty permanently fixed railroad rails driven into the beach (Figures 3 and 4) . The rails extend from the toe of the dunes at the rear of the beach, above the level of the highest normal wave runup, down to the lowest tide level, and are approximately ten feet apart. The eleva- tion of the top of each rail above MLLW was measured by a leveling survey to 0.01 feet relative to benchmarks located in the immediate vicinity. The profile measurements consist of daily sand levels measured at each rail on the beach reduced to an elevation above MLLW (tabulated in Harlett, 1967) . These sand levels were measured with respect to the top of each rail using a graduated, T-shaped staff. The purpose of the T was to bridge the scour depressions that sometimes occurred around the rails, particularly on the lower portion of the beach. In making 14 a measurement, the horizontal bar of the T was oriented parallel to the beach contours. Sand-level measurements were made to the nearest millimeter and are considered accurate to 0.5 centimeters or approximately 0.015 feet. As was mentioned earlier, the measurements were synchro- nized with the daylight occurrence of lower low water when observations could most conveniently be made and the beach was most exposed. This resulted in a standard sampling interval of approximately 24.8 hours or one lunar day. How- ever, when the time of the low-tide observation, progressing approximately 50 minutes from one day to the next, occurred near sundown the next sampling was shifted ahead only 12.4 hours (one-half lunar day) to the morning low tide. Four such "half-intervals" are included in the period of observa- tions, occurring on February 13, and every 15 days thereafter. Using these intervals of observations resulted in all but three of the sampling tides being the lower low tide of the day. The relation of the daily sampling times to the tides is shown in the lower curve of Figure 7. Wave data were recorded continuously over most of the period covered by the beach study using a bottom-mounted, pressure-type wave sensor. The sensor was located about 700 feet directly seaward of the profile at a mean depth of about 30 feet. The resulting analog wave records were manually analyzed for significant height at the sensor depth and wave period, as described later. 15 II. BASIC CONSIDERATIONS It should be noted at the outset that this investigation was based on some important initial considerations. Several assumptions as to the character of beach changes with respect to changing wave parameters were made based on the results of wave-tank and field studies done by others and from examination of the data collected for this study. These assumptions are: (1) that real ocean waves having a specific set of properties will produce a characteristic equilibrium profile in the beach if they remain constant for a sufficient length of time, (2) a beach, therefore, will tend constantly to readjust its profile so as to approach the equilibrium profile associated with the momentarily prevailing wave conditions, and (3) the response of the beach profile to changing wave conditions to a first approximation is suffi- ciently rapid that the profile is fairly close to equilibrium at all times. The first two assumptions are amply supported by numerous laboratory and theoretical studies (Watts, 1954; Rector, 1954; Watts and Dearduff, 19 54; Ippen and Eagleson, 1966; Nayak, 1970). The third assumption was adopted from Thompson and Harlett (1969) and allows the daily sand transports to be correlated with the wave conditions occurring over the same interval of time. From these assumptions, it was concluded that if, at a given time, a beach is steeper (less steep) or at an elevation 16 higher (lower) than the equilibrium profile associated with the wave conditions prevailing, the sand on the beach will be transported offshore (onshore) in order to adjust the beach toward an equilibrium condition, since the littoral drift is negligible, as noted above, for the beach being studied, and the beach is uniform laterally, it is logical to assume that essentially all of the net volume changes computed from daily profile changes are the result of onshore- offshore transport of sand. It is also important to note that the beach observations used in this study were synchronized with the daily occurrence of lower low water. This results in a very nearly repetitive tidal sequence between successive observations as well as tide levels that differ only slightly from one observation to the next. It was assumed that this choice of sampling interval largely filters out or minimizes the effect of the tides, and that most of the beach changes measured are, therefore, attri- butable to changing wave conditions alone. Finally, it should be noted that this study was limited to the exposed intertidal portion of the beach above the lowest daily tide level. The reason for this was the practical difficulty of making measurements in the surf zone. However, it has been demonstrated that the exposed portion of the beach profile above the low tide level behaves very differently from the section to seaward (Rector, 1954; King, 1959; Eubanks, 1968). It is therefore considered that the beach above the 17 low tide level may be studied as a separate unit 18 III. DATA ANALYSIS A. BEACH DATA 1. Computation of Sand Transport Computation of the daily volume transport on and off the beach was based on the assumption that all sand volume changes occurring on the beach represent onshore-offshore transport of sand, as stated previously. Since no profile changes occurred above the highest reach of the waves, the rear of the beach was taken as a landward boundary across which no transport occurred. Thus, if a given rail or point on the profile is selected, the net transport of sand up or down the beach past that point from one observation to the next is given by the sum of the volume changes occurring between all of the rails landward of the point. It was desired to examine the day-to-day volume change over the entire beachface; accordingly, a reference rail was selected at the toe of the beach at approximately the low tide level past which onshore-offshore sand transport to and from the beachface was computed. The rail lowest on the beach which had been continuously accessible at low tide over the period of the study was Rail 17; this rail was, therefore, chosen as the reference rail (Figure 4). The net volume of sand transported onshore or offshore past this rail from one day to the next for a unit beach width (1 foot) was computed according to the procedure illustrated 19 in Figure 5. First, the volume change per unit beach width between two adjacent rails from one observation to the next was approximated by the volume of a trapezoidal solid of unit width as shown in the figure. The volume changes between the successive pairs of rails were then summed from the back of the beach to the reference rail, with the resultant sum being the net volume of sand transported past the reference rail during the period. Net onshore transport past the reference rail, which represents sand gain, was taken as positive, while offshore transport representing sand loss was taken as negative. The net daily sand transports past Rail 17 for the two-month period of the study are shown graphically in Figure 7. These transport values were also cumulated over the two-month period, and are shown in Figure 8. The cumu- lative sand transport represents the net accumulation on or loss of sand from the beach since the beginning of the study. The daily volume transport values past each rail on the pro- file calculated for the two-month period covered by this study are presented in Appendix A. 2 . Computation of Initial Beach Slope In addition to describing daily changes in the beach profile in terms of volume changes, the necessity of describing the condition of the beach before an observed change occurs is apparent from the following considerations. It has been demonstrated by studies in both laboratory and natural 20 w •o «h V) >% <0 -a c 0) o 5 -M < to < *— >* H3 CO + C-3 a W • i X U «-l rH < o a II + -H X ^— * tn c > II * — -«0J <0 in "•""1 1! a 4-» x: > -a <3 < 5 to a> o a, CO 2 21 •o e t> o 4J 0) u 5 V ■»-• <*H a> *M XI o o r-l H ••H -^ « -M Ih «4H 4-» o «r"I (0 % 0) -o .. -H .c o rH r-4 r T 0> -lH X. -iH -rl 0) id U^J X d) a 4-> 4-» T-t S1 o I c XI C •H <0 c^ kl r-i -o 3 o § '0 w (X o r-H «^. rH o J en + -rt CO rH fi +J • ,d o og X o |) || « o a) «0 < 0) fv ■»"! 0) w XI rH r* rH CO c; re V u 1) 3 to fe <0 o >% o H 1-3 H < Q u •H S^ 28 - * X CO En Pi O co 1 Q S CO w > H Eh D D U oo d) H CP ■H fa •»1 P"-5 ••ll»l«««3 29 IV. RESULTS AND INTERPRETATION A. OBSERVED ON SHORE -OFF SHORE SAND TRANSPORTS The onshore-offshore sand transports occurring on the selected beach over the two-month period of the study are presented in histogram form in Figure 7 and cumulated in Figure 8. The daily transports and cumulative transports are plotted against a time scale composed of intervals corresponding to the times between successive beach profile observations. Most intervals on the time scale are equivalent to one lunar tidal cycle or 24.8 hours; however , when two successive daylight occurrences of low water are only 12.4 hours apart the graphed interval is indicated as only half as long. The sampling interval between beach-profile obser- vations is hereafter referred to as a "period" . It has been stated previously that Rail 17 on the profile was used as the reference point for onshore-offshore volume transport computations, and that transports past Rail 17 give a measure of the net day-to-day volume change over essentially the entire beach face. Figure 7 indicates, for example, that 16.7 cubic feet of sand per foot of beach width were moved offshore past Rail 17 during the 24.8 hour interval between the profile measurements on days 1 and 2. Perhaps the most striking feature of Figure 7 is that offshore transport, indicating erosion of the beach face, was normally limited to isolated events of large magnitude lasting 30 only a day or two, in which as much as 156.3 cubic feet of sand per foot of beach width per event was carried past the reference rail. The offshore transport during a 24.8 hour period had a maximum value of 132.5 cubic feet/foot/ period and averaged about 35 cubic feet/foot/period. Onshore transport prevailed during 69% of the period covered by the study, and normally occurred daily over a series of successive days. The magnitudes of onshore daily sand transport were, however, much lower than those of off- shore transport, with the maximum onshore transport of sand past Rail 17 being 47.0 cubic feet/foot/period. Onshore transports averaged only about 15 cubic feet/foot/period, with transports during roughly half the accretion periods being less than 10 cubic feet/foot/period. It may be seen in Figure 7 that transport may change abruptly from one day to the next in both magnitude and direction. Examination of the associated wave data indicates that these changes are sensitive to changes in the waves inci- dent upon the beach. It is apparent that large offshore transports correspond roughly to times of increased wave height although no correlation was found in the magnitudes of these. The graph of cumulative volume transport past Rail 17 from day-to-day, presented in Figure 8, shows the net or cumulative volume change in the beach occurring over the two- month period covered by the study. The first profile measurement 31 of the series was used as the reference point in time for cumulating the transports; however, the volume changes over any period of time desired can be obtained from the figure. In Figure 8 it may be seen that the beach tended to build throughout the two-month period. This trend can be considered to represent a two-month segment of the seasonal cycle occurring on this beach, the segment closely following the extreme winter condition that has been observed to occur in January on California beaches (Shepard, 1950; Johnson, 1971) . B. RELATION BETWEEN VOLUME TRANSPORT AND INCIDENT WAVES In view of the relatively simple nature of the beach being studied and the association that may be observed in Figure 7 between waves and sand transport, it was concluded that it should be possible quantitatively to relate the daily sand transports to the incident waves. In addition to the basic wave parameters H' and T, it was decided to additionally characterize the waves by their initial steepness, y', and power , P . The selection of steepness as a wave parameter seemed logical because of its demonstrated relationship to numerous wave characteristics such as mass transport, breaker height, breaker type, and wave runup. The initial wave steepness is given by y1 = H'/L . For purposes of correlation, it was found that the mean steepness, yIi occurring over the 24.8 -hour interval between beach 32 observations gave the best measure of the wave steepness for use in explaining the volume changes observed on the beach over that interval. The mean steepness over the interval was computed by averaging the steepness at the final observa- tion time with the steepness values calculated every 6.2 hours during the interval preceeding the observation, i.e., 7; = 1/4 [Y; + Y- + Y; + Y£ 1 . ° [ °i °i-6.2 °i-12.4 °i-18.6 J where i represents the beach profile observation time at the end of a period. 'Wave power was selected as a parameter since it is indic- ative of the amount of energy available over a period of time to perform the work of moving sand up and down the beach. Wave power may be determined from the Airy relationship P= (pg/16) (g/2Tr) (H" )2T (f t-lbf /sec-f t) where g is the acceleration of gravity, p is the average den- 3 sity of seawater (2.0 slug/ft ), and T is the dominant wave period. For purposes of correlation, mean wave power over the 24.8 hour interval between beach observations was assumed to give the best measure of power. This quantity was calculated in a manner similar to v ' • o A tabulation of all wave and beach parameters used in this study is given in Table 1. 33 Table 1 WAVE AND BEACH PARAMETERS Wave Parameters »; Deep water unrefracted wave height. Dominant wave period. Mean initial wave steepness Mean wave power. H' — K -, . K . H o d s g Kd = Damping coefficient Ks = Shoaling Coefficient H g = Wave height at sensor depth Extracted manually from wave records. From one profile observation to the next. From one profile observation to the next. Beach Parameters Daily sand transport. Initial mean beach slope above Rail 17. From one profile observation to the next. + = onshore - = offshore At time of profile observation at the beginning of a period . 34 1. Synoptic Wave Events The first step taken toward establishing a relation- ship between beach changes and the incident waves was to construct a graph of synoptic wave events. The ordinates of the graph are H' and T. Two families of curves of y* 3 r o 'o and P', both of which are functions solely of H1 and T, are ' J o ' shown on the graph. These curves do not extend into the area left of the curve labeled "limiting steepness", which, for practical purposes, is taken to be H'/L =0.10. A synoptic wave event is defined as the series of waves arriving on the beach over a period of time from a single generating source, and may be a swell train from a distant storm or wind waves of local origin. By way of illustration, Figures 9A through 9D present selected wave events occurring on the indicated dates. The H'-T combina- tions occurring at beach observation times are indicated by a circled dot and labeled with the date; the H'-T combina- o tions at 6.2-hour intervals in between are indicated by a dot only. These are connected by a directed, continuous time curve from which can be read the height-period combina- tion for the wave train at any moment during its life. On such a graph, swell and wind wave events each have a distinctive form. A swell event, such as the event of February 20 - 22 in Figure 9A, normally begins on the right of the graph with the earliest wave arrivals being of long period and low height. As time progresses the period decreases, and the height increases, with the resulting 35 co w > w w 1 U H E-i G. O 53 >H CO < as w > u H Eh O Z >H CO Q I CQ c^ w a) M CP •H Em 37 height-period "vector" being directed upward and to the left, crossing lines of increasing power and steepness. After the peak height, or power, for the swell train is reached, the vector descends, crossing lines of decreasing power, with steepness either being roughly constant or decreasing. A wind-wave train exhibits a very different character, and is illustrated in Figure 9A by the wave event of March 2-4. The vector representative of wind waves begins in the lower left-hand corner of the graph with small, steep waves. As the wave height builds, the steepness remains large until the peak power is reached; after which the height-period vector descends in a manner similar to that of the waning portion of a swell event. The sand-volume transports occurring between successive beach observations are shown numerically on the appropriate portions of the H'-T curves in cubic feet/foot/period. When the transports are associated with the graphed intervals between beach observations in Figures 9A through 9D a pattern emerges. It can be seen that whenever there is an increase in steepness and power between beach observations, there is normally a corresponding offshore (negative) transport. This is true for both wind wave and swell events. After the peak wave height in an event is passed and the wave heights begin to decrease, the beach normally begins to accrete. It may be noted in Figure 9A, however, that for the wave event of February 13 - 15, offshore transport continued even after the peak height had passed. This lag in response of the 38 beach to changing wave conditions would seem to indicate that for some hours after the wave heights had begun to decrease, the beach was still at a higher elevation, or was steeper, than the equilibrium condition for the wave conditions pre- vailing over that period. This observation is consistent with the argument that on a beach which is initially at an elevation higher than, or has a slope greater than, that of the equilibrium profile for the existing wave conditions, transport will be offshore. It is thus apparent that the initial condition of the beach must be taken into account in any attempt to correlate daily sand transports with the existing wave conditions. 2. Wave-Beach Correlation The relationship between beach changes and the incident wave conditions was examined using an empirical graphical approach. Three-factor graphs were constructed, with transport values being plotted for various logical combinations of the wave and beach parameters listed in Table 1. From the basic considerations given in Section II and from insight gained from the examination of Figures 7 and 9A through 9D, it was determined, following some experi- mentation, that the components of a satisfactory relationship between incident wave conditions and beach response include: (1) the volume transport, V, occurring over the period between two successive beach observations, (2) the mean beach slope, a"., at the beginning of the 39 period, and (3) the mean wave steepness, y"' , over the period between the two successive beach observations. The results of this correlation are presented in Figure 10. This figure contains all of the data for the two-month study with the exception of the data for the period of extremely low waves from March 11 to 22 , during which scatter of the data was extreme. It is apparent from examination of this graph that a reasonably good, first-order relationship exists between these parameters. For each given average wave steepness, for example, there is apparently an equilibrium average beach slope, as indicated by the zero transport curve labeled "equilibrium condition". As the waves become steeper for a given initial beach slope, sand is transported off the beach, the beach is eroded, and that portion of the beach affected by the waves comes to have a gentler average slope. The converse is also true, but the relationship seems less well defined for onshore transports than for offshore transports. This agrees with the qualitative observations of Shepard (1963) and others that waves of low steepness are construc- tive and waves of high steepness are destructive, and with the statement of Wiegel (1964) that "normal" wave conditions tend to move offshore sand toward a beach, while "storm" conditions cause erosion of the beach. 40 .050 .05 5 l« v a o u o V 00 c o .060 .065 .070 H> " 10 100 Figure 10: DAILY SAND TRANSPORT AS A FUNCTION OF WAVE STEEPNESS AND INITIAL- BEACH SLOPE 41 C. THE EFFECT OF WAVE POWER AND THE TIDES Correlations were attempted utilizing wave power as a parameter. No relationship was observed, however, and it was concluded that wave power is probably, at most, of only minor importance in the determination of sand transport values. Similarly, even during the long period of low waves in mid-March when some tidal effects appear to have occurred (Figure 7) , no quantitative relation between the tides and sand transports could be developed. In the final analysis, it is clear from the nature of the variation of the volume transports from day to day that beach changes reflect primarily variably changing wave con- ditions rather than the regular changes of the tides. 42 V. CONCLUSIONS The conclusions reached in this investigation of the daily volume changes over a two-month period in the exposed profile of Del Monte Beach, California, are as follows: (1) Offshore transport of sand from the beachface occurred as isolated events of usually large magni- tude lasting one to two days. Onshore transport occurred over longer intervals of time of up to seven consecutive days and was of relatively small daily magnitude. Onshore transport prevailed during 69% of the period covered by the study. (2) Offshore transport past Rail 17, located at the foot of the beachface, averaged approximately 35 cubic feet of sand/foot of beach width/lunar day (24.8 hours), and had a maximum value of 132.5 cubic feet/ foot/day. Onshore transport, on the other hand, averaged only about 15 cubic feet/foot/day, with the maximum being 47.0 cubic feet/foot/day. The maximum volume of sand carried off the beach during an off- shore transport event was 156.3 cubic feet/foot of beach width, while that returned during an onshore transport event was 189.2 cubic feet/foot. (3) The large offshore transports were normally associated with wind waves or swell of larger steepness and wave heights (H1) of 1 to 5 feet, while the smaller 43 onshore transports were associated with swell of very small steepness and wave heights of less than a foot. (4) Numerous correlation attempts utilizing both wave steepness and power as parameters indicate that wave steepness greatly influences onshore-offshore sand volume transport, while wave power is of generally secondary importance. (5) The onshore-offshore transport of sand during a lunar day (chosen to minimize the effect of the tides) depends to a first approximation upon the mean beach slope at the beginning of the period and the average wave steepness during the period (Figure 10) . If the initial mean beach slope is greater than the slope of the equilibrium profile associated with the existing wave steepness, or if the profile is initially at equilibrium and the wave steepness increases, sand will be moved offshore (the beach will erode) until the equilibrium profile for the new wave conditions is reached. Conversely, if the initial mean beach slope is less than that for the equilibrium profile, or if the wave steepness has decreased, sand will be transported onshore until the equilibrium is reached. The closer to equili- brium the beach is, the smaller the transports are. The results of this study probably generally characterize relatively sheltered sand beaches along coasts where the open-ocean wave regime is generally similar. 44 LIST OF REFERENCES 1. Eubanks, G. E. , 1968. A field study of tide-induced sand movement on Del Monte Beach, California. Naval Postgraduate School, Monterey, California, M.S. Thesis, 52 pp. 2. Harlett, J. C. , 1967. Daily changes in beach profile and sand texture on Del Monte Beach, California. Naval Postgraduate School, Monterey, California, M.S. Thesis, 84 pp. 3. Harrison, W. , et al . , 1968. A time series from the beach environment. Environmental Science Services Administra- tion, Atlantic Oceanographic Laboratories Technical Memorandum No. 1, 28 pp. 4. Haydock, D. G. , 1969. Alteration of a beach profile during a tidal cycle. Naval Postgraduate School, Research Paper in Oceanography, 43 pp. 5. Monterey Bay, California. House Document No. 219, 86th Congress, 1st Session, Appendix V: Shoreline Changes, 27 August 1959. 6. Ingle, J. C. , 1966. The movement of beach sand. Elsevier, 221 pp. 7. Inman, D. L. , and J. Filloux, 1960. Beach cycles related to tide and local wind wave regime. Journal of Geology, V. 68, No. 2, pp. 225-231. 8. Ippen, A. T. , and P. S. Eagleson, eds., 1966. Estuary and coastline hydrodynamics. McGraw-Hill, 744 pp. 9. Johnson, J.W., 1971. The significance of seasonal beach changes in tidal boundaries. Journal of the American Shore and Beach Preservation Association, V 39, No. 1, pp. 26-31. 10. King, C. A. M. , 1959. Beaches and coasts. Edward Arnold, Ltd., London, 403 pp. 11. Nayak, I. V. , 1970. Equilibrium profiles of model beaches. University of California, Hydraulic Engineering Laboratory, Technical Report HEL-2-25, 117 pp. 45 12. Rector, R. L. , 1954. Laboratory study of equilibrium pro- files of beaches. Corps of Engineers, Beach Erosion Board, Technical Memorandum No. 41, 3 8 pp. 13. Rohrbough, J. D. , J. E. Koehr , and W. C. Thompson, 1954. Quasi-weekly and daily profile changes on a distinctive sand beach. American Society of Civil Engineers Pro- ceedings of Ninth Conference on Coastal Engineering, Chapter 16, pp. 249-258. 14. Shepard, F. P., and E. C. LaFond, 1940. Sand movement along the Scripps Institution pier. American Journal of Science, V. 238, pp. 272-285. 15. Shepard, F. P., 1950. Beach cycles in Southern California. Corps of Engineers, Beach Erosion Board, Technical Memo- random No. 20, 26 pp. 16. Shepard, F. P., 1963. Submarine geology. Harper and Row, Second Edition, 557 pp. 17. Strahler , A. N. , 1964. Tidal cycle of changes in an equilibrium beach, Sandy Hook, N. J. Columbia University, Department of Geology, Technical Report No. 7, 51 pp. 18. Thompson, W. C, and J. C. Harlett, 1969. The effect of waves on the profile of a natural beach. American Society of Civil Engineers, Proceedings of Eleventh Conference on Coastal Engineering, Chapter 23, pp. 352- 372. 19. Thompson, W. C, 1972. Wave frequency by the wave- group method. American Society of Civil Engineers, Pro- ceedings of Thirteenth Conference on Coastal Engineering, Abstract. 20. Watts, G. M. , 1954. Laboratory study of effect on varying wave periods on beach profiles. Corps of Engineers, Beach Erosion Board, Technical Memorandum No. 53, 19 pp. 21. Watts, G. M. , and R. F. Dearduff, 1954. Laboratory study of effect of tidal action on wave-formed beach profiles. Corps of Engineers, Beach Erosion Board, Technical Memorandum No. 52, 21 pp. 22. Wiegel, R. L. , 1964. Oceanographical engineering. Prentice-Hall, 532 pp. 46 APPENDIX A DAILY SAND VOLUME TRANSPORTS Transports are in cubic feet of sand/foot of beach width/ period carried past a given rail on the profile, between observations on the dates indicated. A period is the interval of time between two successive beach profile observations. 47 RAIL DATE 2 3 4 5 6 7 8 9 10 11 2/1-2 0.0 0.0 0.4 -0.4 -4.8 -6.8 -8.7 -10.9 -13.3 -15.3 2-3 0.0 0.1 0.4 1.0 0.8 -0.1 -0.6 -0.5 0.4 1.8 3-4 0.0 0.0 0.0 0.2 2.4 4.4 6.4 9.0 11.5 13.8 4-5 0.0 1.5 1.7 -3.6 -22.6 -35.4 -47.2 -58.9 -69.5 -78.9 5-6 0.0 0.6 2.5 4.8 9.9 12.4 14.2 14.9 14.5 13.5 6-7 0.0 0.0 -0.0 -1.9 -2.0 1.5 4.9 7.9 10.0 11.4 7-8 0.0 0.0 -0.0 3.9 15.2 18.8 21.4 22.2 23.0 25.1 8-9 0.0 0. 1 2.0 4.4 4.8 3.0 1.3 1.3 1.8 1.5 9-10 0.0 -0.1 -0.1 0.0 3.2 3.2 3.9 8.7 13.5 18.1 10-11 0.0 0.0 0.0 0.0 1.0 7.7 16.4 22.5 27.6 31.2 11-12 0.0 0.0 0.0 0.0 0.6 2.1 4.5 8.1 12.6 17.2 12-13 0.0 0.0 0.0 0.0 0.0 0.1 0.7 3.9 8.8 12.1 13.14 0.0 0.0 0.1 1.4 6.1 6.2 0.9 -10.7 -25.1 -37.7 14-15 0.0 0.0 0.1 0.1 -1.5 -4.3 -7.6 -10.7 -13.9 -17.2 15-16 0.0 0.0 0.0 0.0 -1.7 -2.1 -1.4 -0.8 -0.8 -1.0 16-17 0.0 0.0 0.0 0.0 4.7 8.4 9.8 9.6 8.2 6.4 17-18 0.0 0.0 0.0 0.1 1.4 1.7 1.7 3.1 5.8 9.2 18-19 0.0 0.0 0.1 0.5 0.5 0.3 1.3 3.3 5.3 6.9 19-20 0.0 0.0 0.0 0.0 3.0 6.0 7.9 9.0 9.7 10.6 20-21 0.0 -0.1 0.3 1.3 -0.7 -3.8 -6.2 -7.9 -8.6 -8.7 21-22 0.0 -0.1 0.1 1.0 0.4 -1.0 -1.6 -1.9 -2.2 -2.3 22-23 0.0 0.0 0.0 0.2 -2.1 -4.1 -3.9 -1.4 2.7 7.7 23-24 0.0 0.2 1.1 -3.1 -15.3 -17.1 -18.1 -18.9 -19.1 -18.9 24-25 0.0 -0.1 -4.7 -8.4 -6.5 -5.9 -5.7 -5.9 -7.2 -9.4 25-26 0.0 0.0 1.0 2.7 5.7 6.8 7.1 6.9 6.1 5.1 48 RAIL DATE 12 13 14 15 16 17 18 19 20 2/1-2 -16.8 -17.9 -18.5 -18.3 -17.7 -16.7 -15.5 -14.1 -13.2 2-3 5.1 8.5 10.0 11.3 12.2 12.8 13.3 13.9 14.3 3-4 14.8 16.2 19.5 23.5 27.9 33.6 39.8 46.4 52.2 4-5 -88.2 -97.3 -106.0 -114.8 -123.1 -132.5 -142.4 -153.5 -163.2 5-6 12.2 8.6 4.8 2.6 0.2 -2.4 -4.7 -5.9 -7.0 6-7 12.0 14.1 16.2 > 16.7 17.8 19.8 22.5 25.7 28.5 7-8 27.3 29.6 31.7 33.8 35.9 38.0 39.5 40.5 41.3 8-9 2.0 3.0 4.9 7.2 9.2 11.0 12.2 13.4 14.7 9-10 20.6 22.3 24.3 25.1 25.2 24.7 24.0 23.0 21.3 10-11 35.6 39-5 41.3 42.6 43.4 44.2 44.6 44.4 44.2 11-12 22.1 27.1 32.1 36.3 39.0 40.0 39.5 38.5 37.7 12-13 13.8 14.7 14.4 13.2 12.4 11.4 10.1 9.0 8.6 13-14 -48.7 -58.2 -64.6 -68.1 -73.1 -77.5 -80.1 -82. 5******* 14-15 -21.6 -29.1 -41.7 -57.1 -69.4 -78 . 8********************* 15-16 -0.9 0.6 3.3 6.0 8.4 10.1********************* 16-17 5.1 4.8 6.8 12.3 19.6 27.6 33 4************** 17-18 13.2 18.8 25.1 31.2 35.6 38.3 40.7 42 5**** *** 18-19 6.3 4.9 4.4 2.8 0.5 -2.2 -4.7 -6.2 -6.7 19-20 13.3 15.6 16.1 17.2 19.0 22.0 26.0 31.2 36.5 20-21 -8.5 -8.0 -7.3 -6.4 -6.0 -6.0 -6.4 -7.0 -7.3 21-22 -2.0 -1.6 -0.8 -0.0 -0.5 0.4 -0.4 -2.5 -5.4 22-23 13.0 18.3 23.1 27.2 30.4 33.2 35.5 37.8 39.5 23-24 -18.2 -17.4 -16.9 -16.5 -16.1 -15.4 -14.5 -14.0 -13.8 24-25 -12.2 -15.3 -17.9 -19.8 -21.0 -22.8 -25.8 -29.3 -33.3 25-26 4.2 3.5 2.5 0.8 -0.9 -2.0 -1.7 -0.2 1.9 49 RAIL DATE 2 3 4 5 6 7 8 9 10 11 26-27 0.0 0.0 0.0 0.0 0.0 0.9 3.2 6.6 10.4 13.0 27-28 0.0 0.0 0.0 0.0 0.2 1.8 5.8 9.6 10.5 10.0 2/28-3/1 0.0 0.0 0.0 0.0 2.2 4.0 4.2 4.4 6.5 10.0 1-2 0.0 0.0 0.0 0.0 1.6 4.1 7.5 10.7 12.4 13.1 2-3 0.0 0.0 0.5 1.2 -3.9 -12.4 -23.6 -35.5 -44.0 -49.8 3-4 0.0 0.0 0.0 0.0 3.4 7.2 10.3 12.7 13.4 12.5 4-5 0.0 0.0 0.0 0.0 0.9 2.0 3.9 5.9 7.4 8.2 5-6 0.0 0.0 0.0 0.0 0.5 1.7 3.4 4.7 5.5 6.3 6-7 0.0 0.0 0.0 0.0 0.2 1.5 4.1 6.6 8.0 8.7 7-8 0.0 0.0 0.0 0.0 1.3 3.1 4.8 5.9 7.0 8.8 8-9 0.0 0.0 0.0 0.0 0.0 0.4 1.8 3.3 3.1 2.3 9-10 0.0 0.0 0.0 0.0 -1.7 -4.1 -9.6 -19.1 -25.3 -26.0 10-11 0.0 0.0 0.0 0.0 3.3 6.3 10.5 19.7 28.3 31.7 11-12 0.0 0.0 0.0 0.0 0.0 0.2 1.8 5.6 10.2 14.2 12-13 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.4 4.7 7.8 13-14 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 2.5 5.2 14-15 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.5 2.6 15-16 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 1.9 4.0 16-17 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.4 1.2 4.1 17-18 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 1.5 18-19 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.7 0.4 -1.7 19-20 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -0.2 -0.3 1.0 20-21 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 1.1 2.5 21-22 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 1.2 50 RAIL DATE 12 13 14 15 16 17 18 19 20 26-27 13.6 12.5 11.4 11.0 11.1 11.6 12.2 12.5 12.7 27-28 9.3 8.7 8.2 7.9 7.9 8.4 9.1 9.7 9.8 2/28-3/1 14.5 19.6 23.6 26.1 26.9 26.5 25.5 23.9 22.7 1-2 13.0 12.0 10.6 9.2 8.1 7.0 5.9 4.9 4.0 2-3 -53.6 -55.5 -55.5 -53.9 -51.4 -48.8 -46.3 -43.3 -40.0 3-4 10.9 9.3 7.5 5.5 3.7 2.6 2.3 2.3 2.6 4-5 8.1 7.2 5.7 3.8 2.0 0.3 -0.9 -1.8 -2.3 5-6 7.4 8.0 8.2 8.7 9.1 9.4 9.4 9.8 10.5 6-7 8.5 7.6 6.1 3.5 1.2 0.4 0.7 1.3 2.1 7-8 11.3 14.4 17.6 21.0 23.7 24.9 25.3 25.5 25.5 8-9 1.4 1.1 1.4 2.0 2.5 2.7 2.4 1.3 -0.3 9-10 -25.2 -25.5 -26.2 -26.8 -26.8 -26.3 -25.3 -23.7 -22.1 10-11 33.3 35.5 37.9 39.8 40.6 40 2_************ ********* 11-12 17.6 20.4 22.5 24.1 25.5 26. 7********************* 12-13 10.0 11.2 11.4 11.1 10.8 10.2 g 3************** 13-14 6.8 7.3 7.8 8.5 9.4 10.6 11. 8************** 14-15 4.7 4.1 2.6 0.4 -2.2 -4.5 -5. 7*,v ************ 15-16 5.9 8.7 9.7 8.5 5.7 2.3 0 9************** 16-17 7.8 10.2 11.9 12.8 12.8 11.7 10 o********** **** 17-18 2.8 4.5 6.0 7.8 9.3 9.5 9.8 11 1******* 18-19 -3.4 -2.4 0.7 5.3 10.7 17.8 22.7 24 o******* 19-20 4.8 7.5 6.1 3.1 0.7 -0.5 -0.2 0.1 0.3 20-21 1.9 0.8 1.9 4.2 6.9 8.7 8.9 9.1 9.6 21-22 0.7 -1.3 -3.3 -5.7 -8.3 -10.4 -10.6 -9.8 -8.8 51 RAIL DATE 23456789 10 11 3/22-23 0.0 0.0 0.0 0.0 0.0 0.0 0.5 2.5 4.1 2.6 23-24 0.0 0.0 0.4 1.4 1.0 -3.3 -11.0 -23.7 -41.2 -58.5 24-25 0.0 0.0 0.0 0.3 5.0 8.1 7.4 4.4 1.1 -3.2 25-26 0.0 0.0 0.0 0.0 -1.9 -0.4 6.9 15.1 20.0 23.2 26-27 0.0 0.0 0.0 0.0 0.0 0.5 1.6 4.1 8.9 15.1 27-28 0.0 0.0 0.0 0.0 0.8 1.3 1.9 1.5 -0.2 -0.9 28-29 0.0 0.0 0.0 0.0 0.5 0.9 -0.5 -2.2 -2.6 -3.4 29-30 0.0 0.0 0.2 1.4 -4.0 -13.7 -24.5 -34.7 -43.4 -51.4 30-31 0.0 0.0 0.0 -1.0 -0.1 2.7 5.4 7.9 9.5 11.1 52 RAIL DATE 12 13 14 15 16 17 18 19 20 3/22-23 2.2 4.9 7.5 9.7 11.8 13.6 14.0 13.7 13.5 23-24 -72.9 -83.3 -88.1 -88.6 -86.6 -83.7 -80.8 -78.3 -77.0 24-25 -8.7 -14.9 -21.0 -27.0 -33.1 -39.7 -46.0 -52.1 -57.0 25-26 25.6 27.5 29.3 30.8 32.1 31.7 30.6 30.1 28.2 26-27 23.3 30.9 35.5 39.7 42.9 47.0 49.7 49.5******* 27-28 -2.3 -3.8 -4.6 -7.3 -10.6 -14 . l********************* 28-29 -4.2 -4.2 -3.6 -2.2 -0.3 3.0********************* 29-30 -59.8 -67.7 -74.0 -78.9 -82.6 -85.2 -86.5 -86.9 -86.3 30-31 12.7 13.4 14.1 15.1 16.3 17.6 18.3 17.7******* * INDICATES RAIL WAS INACCESSABLE 53 APPENDIX B WAVE AND TIDE DATA Wave height at sensor depth, H , dominant wave period, T, y hydrodynamic damping coefficient, K , , shoaling coefficient, K , and deep water unrefracted wave height, H' . are tabulated s o every 6.2 hours with the date, time, and tide height (relative to MLLW) being given additionally for the times of beach pro- file observations. Wave data for February 1-13 and 18-20 are not tabulated. 54 OBSERVATION TIME DATE (Time of LLW) TIDE 2/14 0750 1.8 2/15 0844 1.6 2/16 0950 1.3 2/17 1056 0.9 2/21 1432 -0.9 2/22 1514 -1.2 H g T Kd Ks H' o 0.75 5.0 2.575 1.078 2.08 1.00 5.7 1.950 1.094 2.13 1.60 6.0 1.841 1.095 3.23 2.20 6.0 1.841 1.095 4.43 1.75 5.8 1.900 1.095 3.64 1.60 5.6 1.948 1.093 3.41 1.30 5.0 2.575 1.078 3.61 1.10 4.0 5.245 1.033 5.96 1.15 12.8 1.119 0.920 1.18 0.90 12.0 1.143 0.943 0.97 0.75 11.2 1.168 0.967 0.85 0.90 10.4 1.199 0.991 1.07 0.95 20.0 1.048 0.761 0.76 0.90 19.0 1.053 0.778 0.74 0.90 17.9 1.060 0.799 0.76 1.20 16.5 1.072 0.830 1.07 0.90 19.2 1.052 0.775 0.73 1.05 18.4 1.057 0.790 0.88 1.14 17.6 1.062 0.805 0.97 1.15 16.8 1.069 0.823 1.01 1.11 16.0 1.076 0.840 1.00 0.75 15.2 1.085 0.860 0.70 0.50 14.4 1.096 0.878 0.48 0.37 13.6 1.108 0.898 0.37 0.37 13.8 1.105 0.894 0.37 55 OBSERVATION TIME DATE (Time of LLW) TIDE 2/23 1556 -1.2 2/24 1632 -1.1 2/25 1714 -0.7 2/26 1750 -0.1 2/27 1832 0.6 2/28 0720 0.5 3/1 0832 0.3 H g T Kd Ks o 0.43 18.4 1.057 0.790 0.36 0.50 17.8 1.061 0.801 0.42 0.60 16.9 1.068 0.820 0.53 0.66 16.0 1.076 0.840 0.60 0.61 15.1 1.086 0.861 0.57 0.53 14.2 1.098 0.884 0.51 0.37 14.0 1.102 0.888 0.36 0.35 14.6 1.093 0.874 0.33 0.63 14.8 1.090 0.869 0.60 1.44 14.8 1.090 0.869 1.36 1.75 14.4 1.096 0.878 1.68 1.24 13.1 1.118 0.912 1.26 0.77 12.8 1.119 0.920 0.79 0.77 11.9 1.145 0.947 0.83 0,72 11.2 1.168 0.967 0.81 0.56 10.8 1.180 0.978 0.65 0.41 10.4 1.199 0.991 0.49 0.33 10.0 1.216 1.003 0.40 0.33 9.7 1.230 1.012 0.41 0.40 10.8 1.180 0.978 0.46 0.40 12.0 1.143 0.943 0.43 0.54 13.8 1.105 0.890 0.53 0.59 13.1 1.118 0.912 0.60 0.60 12.3 1.132 0.935 0.64 0.58 14.2 1.098 0.884 0.56 56 OBSERVATION TIME DATE (Time of LLW) TIDE 3/2 0944 0.1 3/3 1056 -0.1 3/4 1208 -0.3 3/5 1314 -0.5 3/6 1408 -0.6 3/7 1450 -0.6 H g T Kd K s H1 o 0.58 13.7 1.107 0.896 0.58 0.65 13.1 1.118 0.912 0.66 0.62 12.2 1.136 0.937 0.66 0.80 9.6 1.237 1.015 1.00 1.10 9.7 1.230 1.012 1.37 1.20 9.8 1.224 1.009 1.48 1.65 10.0 1.216 1.003 2.01 1.40 10.2 1.210 0.997 1.69 1.41 10.3 1.200 0.994 1.68 1.20 10.3 1.200 0.994 1.43 0.72 10.4 1.199 0.991 0.86 0.75 10.5 1.195 0.987 0.88 0.65 11.2 1.168 0.967 0.73 0.50 10.7 1.188 0.982 0.58 0.55 10.2 1.210 0.997 0.66 0.55 9.6 1.237 1.015 0.69 0.40 10.0 1.216 1.003 0.49 0.45 12.6 1.124 0.926 0.47 0.54 12.6 1.124 0.926 0.56 0.33 11.9 1.145 0.947 0.36 0.34 11.4 1.159 0.962 0.38 0.38 10.7 1.188 0.982 0.44 0.39 10.0 1.216 1.003 0.48 0.40 14.1 1.100 0.886 0.39 0.55 13.0 1.120 0.914 0.56 57 OBSERVATION TIME DATE (Time of LLW) TIDE 3/8 1526 -0.4 3/9 1556 -0.2 3/10 1626 0.1 3/11 1650 0.5 3/12 1720 0.9 3/13 1744 1.3 3/14 0626 1.0 H g T Kd Ks H' o 0.51 11.9 1.145 0.947 0.55 0.59 10.8 1.180 0.978 0.68 0.55 10.0 1.216 1.003 0.67 0.43 9.3 1.256 0.024 0.55 0.51 8.4 1.325 1.052 0.71 0.50 8.0 1.373 1.063 0.73 0.31 7.7 1.410 1.074 0.47 0.26 7.6 1.425 1.078 0.40 0.30 9.0 1.278 1.034 0.40 0.37 10.8 1.180 0.978 0.43 0.35 12.5 1.127 0.928 0.37 0.65 12.8 1.119 0.920 0.67 0.66 12.8 1.119 0.920 0.68 0.90 14.4 1.095 0.878 0.87 1.10 13.7 1.107 0.896 1.09 0.65 12.6 1.124 0.926 0.68 0.34 12.0 1.143 0.943 0.37 0.55 11.4 1.159 0.962 0.61 0.35 10.5 1.195 0.987 0.41 0.30 12.3 1.132 0.935 0.32 0.40 11.8 1.149 0.950 0.44 0.45 11.5 1.160 0.959 0.50 0.51 11.0 1.174 0.973 0.58 0.54 10.6 1.189 0.985 0.63 0.40 10.3 1.200 0.994 0.48 58 OBSERVATION TIME DATE (Time of LLW) TIDE 3/15 0708 0.9 3/16 0802 0.7 3/17 0902 0.6 3/18 1008 0.4 3/19 1120 0.1 3/20 1220 -0.2 H g T Kd Ks H' o 0.30 9.7 1.230 1.012 0.37 0.19 9.2 1.264 1.028 0.25 0.20 8.7 1.300 1.044 0.27 0.13 8.9 1.284 1.037 0.17 0.25 10.3 1.200 0.994 0.30 0.24 13.9 1.103 0.891 0.24 0.18 14.2 1.098 0.883 0.17 0.20 13.6 1.108 0.898 0.20 0.39 12.8 1.119 0.920 0.40 0.42 12.2 1.136 0.937 0.45 0.40 11.5 1.160 0.959 0.44 0.38 10.9 1.179 0.976 0.44 0.36 10.2 1.210 0.997 0.43 0.37 9.4 1.250 1.021 0.47 0.40 15.4 1.079 0.845 0.36 0.34 15.1 1.086 0.861 0.32 0.54 14.4 1.096 0.378 0.52 0.54 13.7 1.107 0.896 0.54 0.50 13.1 1.118 0.912 0.51 0.46 12.2 1.136 0.937 0.49 0.40 12.0 1.143 0.943 0.43 0.30 11.9 1.145 0.947 0.33 0.20 11.9 1.145 0.947 0.22 0.14 11.7 1.152 0.953 0.15 0.35 11.2 1.168 0.967 0.40 59 OBSERVATION TIME DATE (Time of LLW) TIDE 3/21 1314 -0.5 3/22 1356 -0.7 3/23 1438 -0.8 3/24 1520 -0.6 3/25 1556 -0.3 3/26 1638 +0.3 H g T Kd Ks H' o 0.40 10.4 1.199 0.991 0.48 0.50 9.8 1.224 1.009 0.62 0.36 9.2 1.264 1.028 0.47 0.42 8.8 1.291 1.040 0.56 0.25 8.6 1.308 1.047 0.34 0.24 8.4 1.325 1.053 0.33 0.12 8.3 1.337 1.055 0.17 0.15 8.5 1.316 1.050 0.21 0.10 9.0 1.278 1.034 0.13 0.49 9.8 1.228 1.009 0.61 0.30 10.6 1.191 0.988 0.35 1.00 5.2 2.320 1.085 2.52 0.98 19.8 1.049 0.765 0.79 1.05 4.0 5.245 1.033 5.69 1.31 5.5 1.970 1.091 2.82 1.44 6.5 1.660 1.092 2.61 1.12 7.0 1.533 1.086 1.86 0.90 6.7 1.600 1.090 1.57 0.68 6.0 1.841 1.095 1.37 0.61 15.7 1.079 0.848 0.56 0.61 15.2 1.085 0.860 0.57 0.60 14.9 1.088 0.865 0.56 0.60 14.4 1.095 0.878 0.58 0.59 14.1 1.100 0.886 0.58 0.54 13.8 1.105 0.894 0.53 60 OBSERVATION TIME DATE (Time of LLW) TIDE 3/27 1714 +0.9 3/28 1756 1.6 3/29 0702 -0.6 3/30 0808 -0.6 3/31 0914 -0.5 H g T Kd K s h; 0.49 13.5 1.110 0.920 0.50 0.46 6.5 1.660 1.092 0.83 0.39 7.2 1.490 1.083 0.63 0.38 7.0 1.533 1.086 0.63 0.40 5.6 1.948 1.092 0.85 0.37 5.4 2.000 1.090 0.81 0.65 8.0 1.373 1.063 0.95 1.10 7.5 1.440 1.076 1.70 1.60 6.2 1.760 1.094 3.08 1.30 5.4 2.000 1.090 2.83 1.35 14.2 1.098 0.884 1.31 1.00 13.0 1.119 0.914 1.02 1.00 12.0 1.143 0.943 1.08 0.86 11.0 1.174 0.973 0.98 1.35 12.5 1.127 0.928 1.41 3.10 14.8 1.090 0.869 2.94 61 APPENDIX C MEAN BEACH SLOPES at the time of the beach profile observations on the date indicated. DATE a DATE a DATE a DATE a 2/1 .0631 2/16 .0648 3/3 .0541 3/18 .0658 2/2 .0559 2/17 .0614 3/4 .0549 3/19 .0591 2/3 .0551 2/18 .0615 3/5 .0565 3/20 .0632 2/4 .0463 2/19 .0614 3/6 .0565 3/21 .0629 2/5 .0572 2/20 .0675 3/7 .0566 3/22 .0571 2/6 .0620 2/21 .0593 3/8 .0568 3/23 .0592 2/7 .0631 2/22 .0587 3/9 .0567 3/24 .0526 2/8 .0664 2/23 .0630 3/10 .0535 3/25 .0598 2/9 .0533 2/24 .0587 3/11 .0586 3/26 .0599 2/10 .0546 2/25 .0537 3/12 .0603 3/27 .0564 2/11 .0518 2/26 .0548 3/13 .0609 3/28 .0591 2/12 .0523 2/27 .0544 3/14 .0596 3/29 .0668 2/13 .0605 2/28 .0539 3/15 .0611 3/30 .0516 2/14 .0686 3/1 .0553 3/16 .0617 2/15 .0655 3/2 .0615 3/17 .0628 62 INITIAL DISTRIBUTION LIST No. Copies 1. Defense Documentation Center 2 Cameron Station Alexandria, Virginia 22314 2. Library, Code 0212 2 Naval Postgraduate School Monterey, California 93940 3. Professor Warren C. Thompson 5 Department of Oceanography Naval Postgraduate School Monterey, California 93940 4. Ensign J. D. Williamson 2 1727 Caddell Lane Norman, Oklahoma 7 3 069 5. Professor E. Thornton 1 Department of Oceanography Naval Postgraduate School Monterey, California 93940 6. Department of Oceanography 3 Naval Postgraduate School Monterey, California 93 940 7. Oceanographer of the Navy 1 The Madison Building 732 N. Washington Street Alexandria, Virginia 22314 8. Dr. Ned A. Ostenso 1 Code 480D Office of Naval Research Arlington, Virginia 22217 9. Evelyn L. Pruitt, Director 1 Geography Programs, Code 414 Office of Naval Research Department of the Navy Washington, D. C. 20360 10. Commanding Officer 2 Fleet Numerical Weather Central Monterey, California 93940 63 No. Copies 11. Coastal Engineering Research Center 5201 Little Falls Road, N. W. Washington, D. C. 20016 12. Mr. Charles Fisher, Chief Coastal Engineering Branch U. S. Army Corps of Engineers P. 0. Box 2711 Los Angeles, California 90053 13. Commanding Officer San Francisco District U. S. Army Corps of Engineers • 100 McAllister Street San Francisco, California 94102 Navigation and Shoreline Planning Section Library 14. Coastal Engineering Branch Planning Division U. S. Army Engineering Division, South Pacific 630 Sansome Street San Francisco, California 94111 64 Security Classification DOCUMENT CONTROL DATA -R&D {Security clas silic ation of title, body of abstract and indexing annotation must be entered when the overall report Is classified) ORIGINATING ACTIVITY (Corporate author) Naval Postgraduate School Monterey, California 93940 Za. REPORT SECURITY CLASSIFICATION Unclassified 26. GROUP REPORT TITLE Onshore-Offshore Sand Transport on Del Monte Beach, California DESCRIPTIVE NOTES (Type of report and.lnclus ive dates) Master's Thesis; September 1972 au THO RiSl (First name, middle initial, laat name) John David Williamson REPOR T D A TE September 1972 7«. TOTAL NO. OF PAGES fifi 76. NO. OF REFS 22 CONTRACT OR GRANT NO. PROJEC T NO. 9*. ORIGINATOR'S REPORT NUMBERIS) B6. OTHER nc POfl T NOISI (Any other numbers that may be assigned this report) DISTRIBUTION STATEMENT Approved for public release; distribution unlimited. ABSTR AC T Daily sand beach profile d continuously di filtered out by Offshore sa day duration, a width/lunar day up to seven day Onshore-of f first approxima and the initial is greater (les ing wave condit the v/ave steepn (onshore) . The transports are. volume transport values were calculated for a selected uring a two-month period. Wave data were recorded rectly seaward of the profile. Tide effects were largely use of a lunar day (24.8 hour) sampling interval. nd transport occurred in isolated events of one to two- nd had a maximum value of 132.5 cubic feet/foot of beach Onshore transport occurred over longer intervals of s, and had a maximum value of 47.0 cubic feet/foot/day. shore transport over a 24.8 hour period depends, to a tion, on the mean wave steepness incident upon the beach beach slope for the period. If the initial beach slope s) than the equilibrium slope associated with the exist- ions, or if the profile is initially at equilibrium and ess increases (decreases) , sand will be moved offshore closer to equilibrium the beach is, the smaller the )D ,F°o":..1473