Transcript

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MP 4 -70I

TRACING SAND MOVEMENT IN~ THlE LITTORAL ZONE:PROGRESS

IN THE, RADIOISOTOPIC SANDTRACER (RIsT-) STUDYjJuly 1968 -February 1969byI

David B. Duane

MISCELLANEOUS PAPER NO. 4 -70

AUGUIST 19I7-0 ROrdJdbte

* * or Federal Scientific & TechnicalInformation Springfield Va. 22151

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U. S. ARMY, CORPS OF ENGINEERS 4COASTAL ENGINEERING

RESEARCH CENTER

This document has been approved for public release and sale;

its distribution is unlimted.

RI~eri fit o1- I-epub I i Catoi Of m' ofY01 tili ae!T)ha 11 give appropriate credlit to the U . S. d'rmv Laast

g linci-r ig Researchi Center.

LJir;1.itcd free distribution within tile Un tced State:,o f single copies of this publication is m.,ade by:

Coastal Engineering Research Center,5-20.1 Litticq ..Falls Road, N. W.Wa~.hington, D. C. 20016

Contents of this report are not, to be used for adver-tising, publication, or promotional purposes. Citation oftradec names does not constitute an official endorsement Or

ZapproVal Of the Use Of Such commercial p~roduicts.

"'he findings in this report are nct to be cOnstrueJias a officizal Department of the Army posi ti on unless sodes ignat ed by Other authiori zed documeInts.

TRACING SAND MOVEMENT INTHE LITTORAL ZONE:PROGRESS

IN THE RADIOISOTOPIC SANDTRACER (RIST) STUDY

July 1968 - February J969by

David B. Duane

MISCELLANEOUS PAPER NO. 4 - 70

AUGUST 1970

U. S. ARMY, CORPS OF ENGINEERS

COASTAL ENGINEERINGRESEARCH CENTER

This document has been approved for public release and sale;its distribution is unlimited.

ABSTRACT

The Coastal Engineering Research Center, in cooperation with theAtomic Energy Comission, initiated a multiagency program to create aworkable radioisotcpic sand tracing (RIST) program. Tagging procedures,instrumentation, field surveys and data handling techniques were de--reloped which permit collection and analysis of over 12,000 bits ofinformation per hour over a survey track of approximately 18,000 feet.Data obtained can be considered as nb.rly synoptic observations of sedi-ment transport in a single environmental zone or in adjacent beach, surfand offshore zones.

Studies at Surf, California, indicate that sand labeled with theradioisotope of gold 198-199 provides much more data for analysis ofsediment movement than does sand labeled with xenon-133. Surveys con-ducted confirm that, in response to any given set of wave conditions, avery different rate of sediment movement occurs in the zones between thehigh water line and -15 feet mean lowdr low water, Because of thesedifferences, tracing surveys confined solely to the foreshore or offshorezone produce data only partially indicative of transport in the zone ofimmediate concern to coastal engineers. While an accurate determinationof sediment drift volume remains illusive, qualitative data on sedimentmovement useful for engineering purposes can be obtained on a scaleheretofore unattainable.

FOREWORD

Since July 1966, the Coastal Engineering Research Center (CERC) hasdirected a multiagency program to develop a workable sand-tracing systemcapable of operating on the beach, in the surf zone, and offshore. Theprimary effort is toward the use of radioactive tracers to understand themechanics, pattern and volume of sediment movement. Results to June 1968were summarized in "Radioisotopic Sand Tracer Study, Point Conception,California", May 1969, by D. B. Duane and C. W. Judge. That report is nowout of print; copies may be purchased from the Clearinghouse for FederalScientific and Technical Information, 5285 Port Royal Road, Springfield,Virginia 22151. The catalog number is AD 690 804

This report was prepared by D. B. Duane, Chief, Geology Branch andRIST program director, under the general supervision of G. M. Watts, Chief,Engineering Development Division. It is part of Contract AT(49-Il)-2988(as modified) betwoen the Atomic Energy Commission (AEC) and CERC. Workof the AEC is provided through the Oak Ridge National Laboratory (ORNL).Other participants in the present west coast studies are: U. S. Army

*Engineer District, Los Angelqs, U. S. Army Mobility Equipment Command,

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iFirst Strategic Aerospace Division of the Air Force, U. S. Navy PacificMissile Range, Nuclear Systems and Space Power Division, National Aero-nautics and Space Administration (NASA), and Department of Water Resources,State of California.

The contributions of all participants in the program havm been out-standing. Particular appreciation is expressed to the following:

0. M. Bizzell, Division of Isotope Development, AECT. B. Kerr, Nuclear Systems and Space Power Division, NASA •R. R. Baray, First Strategic Aerospace Division, Vandenberg AFBE. Rhodes, U. S."Navy Pacific Missile RangeColonel J. Irvine, Jr., Western Area Office, Los Angeles DistrictHal Leeson, Department of Water Resources, State of CaliforniaJ. H. Bittner, T. A. Bertin, and the field crews and technicalpersonnel of the Los Angeles District.

This report has benefited from comments and suggestions fromF. N. Case, E. H. Acree, and H. R. Brashear of ORNL, and C. W. Judge,P. A. Turner, and W. R. James of CERC.

At the time of publication, Lieutenant Colonel Edward M. Willis wasDirector of CERC: Joseph M. Caldwell was Technical Director.

NOTE: Comments on this paper are invited. Discussion will be publishedin the next issue of the CERC Bulletin.

This report is published under authority of Public Law 166, 79thCongress, approved July 31, 1945, as supplemen;ed by Public Law 172, 88thCongress, approved November 7, A963.

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CONTENTS

Page

Section I. INTRODUCTION ...... .... ..................... 1

1. Background ........ ... ....................... 12. Scope and Objectives ...... .. .................. 3

Section II, ISOTOPES, TAGGING TECHNIQUES, AND INSTRUMENTS . . . . 4

,. Isotopes and Tagging Techniques ..... .............. 42. Injection Devices ...... ....... ............. S3. Detector and Onboard Data Collection System . . ... ... 74. Computer Program ..... ..... .................... 8

Section Ill. FIELD TESTS ..... ...... ...... ... 13

1. General Program Design ................. 132. Xenon Experiments ....... .................... ... 13

3. Results of Xenon Experiments ..... .............. ... 194. Gold Experiments ....... .................... 24S. Results of Gold Experiments .... ............... .... 25

Section IV. COMPARISON OF THE RIST SYSTEM WITH OTHER ARTIFICIALTRACING METHODS ..... ................... .... 36

I. General .............. . ..... .. 362. Comparison of RIST to Other Sediment Transport'Studies . 39

Section V. SUMMARY ...... .. ....................... .... 42

LITERATURE CITED ..... ..... .. ....................... 45

ILLUSTRATIONS

Table Pag

I SU1NARY OF INJECTIONS ...... ................ ..... 17

F gure

1. Study Area. Actual site of tracing operations was onVandenberg Air Force Base property .... ............ 2

2. Cumulative size frequeicy curves .... ............. . 6

3. Packet of gold-tagged sand ...... .. ................. 7

4. Tagged sand carrier dispenser installed on stern of LARC XV. 8

V

I LLUSTRATIONS (Continued)

5. Amphibious LARC XV towing radiation detector vehicleentering surf ..... ...... ........................ 9

6. Onboard data acquisition system ..... ............. . ... 11

7. Computer listing of RIST data ..... ............... .... 12

8. Detail of study area ..... .. .................... ... 14

9. Profiles normal to the shore ... ................ .!.. 5

10. Schematic illustration of RIST tracing operations ... ...... 16

11. Pattern of xenonated sand immediately after release .. ..... 18

12. Pattern of xenonated sand approximately 24 hours afteremplacement ...... ... ......................... .... 20

13. Littoral transport summary, xenon experiments .. ........ 21

14. Sea and swell summary, xenon experiments .. ......... ... 22

15. Location of cores along profiles 50 feet upcaost ... ...... 23

16, Dispersal pattern of gold-tagged sand approximately 2 hoursafter injection ..... ...... ....................... 26

17. Dispersal pattern of gold-tagged sand approximately 4 hoursafter injection ...... .. ....................... .... 27

18. Dispersal pattern of gold-tagged sand approximately T4 hoursafter injection ...... .. ....................... .... 28

19. Dispersal pattern of gold-tagged sand 2 hours after injectiIn 29

20. Dispersal pattern of gold-tagged sand observed approximatelyI hour after the pattern depicted in Figure 19 .... ...... 30

21. Pattern of gold-tagged sand observed 4 days subsequent to

the survey depicted in Figure 20 .... .............. ... 31

22. Littoral drift summary, gold experiment ... ........... 32

23, Sea and swell summary, gold experiments .. ........... .... 33

24. Changes in radioactive gold 198-199 spectrum resulting fromburial of non-radioactive (dead) sand ... ........... ... 37

25. Comparison of tagged sand dispersal patterns ..... ...... 43

VI

TRACING LITTORAL SAND MOVEMENT: RADIOI3OTOPIC SAND TRACER (RIST) STUDY

Progress July 1968 - February 1969

Section I. INTRODUCTION

I. Background

In 1966, the U. S. Army Coastal Engineering Research Center(CERC)-, in cooperation with the Atomic Energy Commission (AEC), initiateda Radioisotopic Sand Tracer (RIST) Investigation of Littoral Transportaround Point Conception, California. Program objectives were: (a) astudy and selection of suitable radioisotope(s); (b) development of radi-ation detection equipment capable of operating on the beach and in thenearshore waters to depths of 100 feet; and (c) trace the movement oftagged sand in the littoral zone.

A major part of the development of hardware and tagging techniqueswas done by AEC's Oak Ridge National Laboratory (ORNL) at Oak Ridge,Tennessee. Other direct participants in the study in fiscal year 1969were U. S. Navy Pacific Missile Range; U. S. Air Force First StrategicAerospace Division; U. S. Army Engineer District Office in Los Angeles;I. S. Army Mobility Comand; National Aeronautics and Space Administra-"on; and the Division if Water Resources, State of California.

Results of this program through June 1968 have been summarizedpreviously (Duane and Judge, 1969; Acree, et al, 1969). This paperis a report on progress of the program since June 19680 especially onvarious aspects of sediment movement on the beach and nearshQxe zone asdepicted by experixents at Surf, California, during September-October1968, and February 1969 (Figure 1).

Since 1968, result; of several different field experiments innuclide tracers have been published. Coatois and Monaco (1969) reporton tests carried out along the French Mediterronean Coast in water 12 to1S feet deep, using chromium 51 and iridium 9S a5 the tagging isotopes.The French experiment established sediment dispers& patterns over aperiod of 1 month.

The U. S. Army Engin~ev Waterways Experiment Station (WES),Vicksburg, Mississippi, recently completed a survey in the Houston ShipChannel (Hart, 1969). The isotope, gold-198, was mixed 2n solution withsediment at the site. The experiment lasted about 2 week:.

Several studies using fluorescent tracers have been reported re-cently-. Kennedy and Kauba (1968) in a U. S. Geological Survey (USGS)open-file report, present results of-studies in sediment transport atClear Creek, Colorado. At the University of Florida, the Departmentof Coastal and Oceanographic Engineering has been experimenting with

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Figure 1. Study Area. Actual site of tracing operations was onVandenberg Air Force Base property immediately northof Surf, California.

2

fluorescent tracing in the marine environment for several years. Resultsof recent studies, carried out on the east coast of Florida, are sum-marized by Stuiver and Purpura (1969). Komar (1969) reports on resultsof the use of fluorescent tracers on two beaches in southern California.McArthur (1969) discusses sand movement related to beach topography nearPanama City, Florida, as indicated by fluorescent tagged sand. Some ofthese investigations are discussed in more detail in Section IV.

2. Scope and Objectives

The RIST Study is a multiagency program directed by CERC todevelop techniques and technology to utilize radioactive-tracer methodsfor research into sand movement and littoral processes. Detailed dis-cussion of the scope and objectives of the overall plan were presentedpreviously (Duane and Judge, 1969). Within the comprehensive frameworkof the program, the scope and objectives of these recent studies atSurf, California (Figure 1), follow:

(a) Compare patterns of sediment movement observed in radio-active sand tracer tests in the Shore Processes Test Basin (SPTB),(Taney, 1963; Duane and Judge, 1969) with patterns observed on anatural sand beach;

(b) Observe nearly synoptical patterns of sediment movement onthe beach face, in the inshore and offshore zones;

(c) Compare results obtained using sand tagged with xenon-133

with those obtained using sand tagged with gold *198-199;

(d) Field test the upgraded data acquisition system; and

(e) Obtain a comparison of littoral transport under differentwave conditions by conducting tests during different seasons.

To obtain initial "data for the program objectives, two experimentswere conducted during the fall of 1968, The first series used sandtagged with xenon-133 placed at two different times as a simulated lne

source extending from the beach face through the su.-f zone. This seriesof injections and subsequent tracing operations were fros 25 to 29September 1968. The second series was conducted using sand t2gged withgold 198-199. To replicate the preceding xenon experiLets, gold-taggedsand was alio placed as a simulated line source extending frox the beachface through the surf zone. Injection was made on 4 and 5 October 1968,and dispersion monitored through 9 October 1968.

During February 1969, another field test using gold 198-199 wasconducted at Surf. Two simultaneous line injections were made extendingfrom -6 to -14 feet mean lower low water and -21 to -27 feet mean lowerlow water. Equipment problens and high wrves prec!uded offshore opera-tions; tracing was confined to the'beach.

This paper will describe operations and procedures used, and givea preliminary analysis of the results of the experiments.

Section II. ISOTOPES, TAGGING TECHNIQUES, AND INSTRUMENTS

1. Isotopes and Taggirg Techniques

Two isotopes were used in this series of tests - xenon-153 witha half-life of 5 days and a mix of gold 198-199 with a halt-life ofabout 3 days.

Radioactive xenon is injected into the quartz grain in a processlike that of kryptonation described by Chl6ck, et al., (1963). Inessence, the process involves heating carbonate-free quartz sand toapproximately 900 degrees centigrade in an atmos5phere of xenon-133, thencooling rapidly with liquid nitrogen. Labeling is a function of the massof the particle and does not affect the hydraulic characteristics of thegrain. Xenon~tion has been described in detail by Acr'ee, et al., (1969).

Isotopes of gold were used in numerous sediment tracing programs(Krone, 1960; Cummins, 1964; Ingram, et al., 1965; and Hart, 1969).However, the tagging procedures have not been explained in detail. Aspart of one of the RIST objectives - the search for isotopes and taggingtechniques suitable for sand tracing - the Oak Ridge National Laboratory(ORNL) initiated a study of existing gold-tagging techniques, andexplored possible improvements. As a result of this research, a newtagging technique was developed (Stephens, et al., 1968) and utilizedin RIST programs. The new technique involves pretreating carbonate-free quartz sand with a solution of p-isopropylbenyaldchyde-ethanol.After washin6 and drying, the sand ir treated with a solution of gold Fchloxide containing the gold isotopes 198 and 199. After decanting ex-cess solution, the sand is cured by heating to 1,000 degrees centigrade.Leaching and abrasion tests show insignificant loss and An inclusiveprocess efficiency of 90 percent.

Because this new ORNL tchnique labels the surface, two drawbackswere possible. One was inhomogeneous tagging on a mass basis becauseof the wide rarge of surface areas present in natural sands consistingof a range of particle sizes. A second was the possible effect onhydid'ulic.characteristics of the grains. Stephens, et al., (1969)found that mass labeling could be approximated by fractionatii:g thesand prior to tagging, and then labeling each fraction with the requi-site proportion of total sample activity of gold 198-199. While theirdata indicate some differences in activity (counts per milligram)among the size classes, counts reported from all size classes have

*no significant statistical difference.

4

In the samples so far tested, the sand grains are slightly modifiedby tagging. In both xenonated and gold-tagged sand a color change isnoticeable.

The untagged sand, after being leached i: hydrocholoric acid, wasmedium grained (X = 1.7; .31 im), was largely quartz with accessoriesof feldspars, metamorphic rock fragments, and heavy minerals; and was4light gray in color (Munsell color code 2.5 Y 7/2 or 10 YR 7/2).

Xenonated sand was medium grained (Xk = 1.6; .33 mm), color wasgray (7.5 YR 6/0). No noticeable change in grain morphology occurredalthough some agglomeration was noted, and was attributed to fusion ofsome grains in contact with the heating elements of the xenonationfurnace during labeling.

The gold-tagged sand has a weak red color (2.5 YR 5/2). and althoughafter tagging it still lies in the medium grain class (X, = 1.97; 25 mm),it is shifted to the extreme fine end of the class and the number of sizeclasses (variance) is narrowed (Figure 2). Some agglomeration of thegold-tagged sand occurred due to accidental overheating during the curing.

Differences between size characteristics of the gold-labeled andunlabeled sand are more difficult to explain than the small amountof agglomeration, and size analysis of gold-tagged sediments used infsubsequent studies continues. Reproducibility in the size gradationprocess is much better than the difference., apparent in Figure 2, andis therefore not considered as a cause for the deviations. As the sizecharacteristics of the actual gold-tagged sand were within the rangeof characteristics of the sand at the test site, it is judged that nodeleterious effects were thus introduced into the experiment. No de-tectable difference in specific gravity (2.65) of the sand occurred asas a result of the gold tagging;none was anticipated because only a fewmilligrams of metallic gold are used in tagging a liter (about 1,500grams) of sand.

2. Injection Devices

As an improvement upon previously used emplacement techniques,water-soluble plastic bags were utilized. Available in different thick-uesses Fid hot-water and cold-water types, this polyvinyl alcohol mate-rial has proved to be very useful. The cold-water variety is used anddissolves in 20 to 30 seconds in the limited temperature range tested(19-21 degrees centigrade). The ORNL packages tagged sand which arrivesat the site ready for use. Prepackaging greatly facilitates field-sitehandling, and makes safety considerations simpler. Xenonated sand ispacked in 1-liter quantities which are handled easily with long-handledtongs.

Gold-tagged sand, packaged in small packets of approximately 15 grams,is placed in a slotted rod fitted inside a shielded cylinder (Figure 3).

5

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size distribution of sand used in the reported experiments.Analysis by rapid sediment analyzer. (RSA)

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Figure 3. Packet of gold-tagged sand. When the watersoluble packaging material dissolves (approximately 30seconds) the tagged sand is free to move as individualparticles responding to waves and currents.

Based on exper.mental results of Pirie (1965), who studied the settlingrates of granule- and pebble-sized particles (2 to 64 rillimeters), thepackets containing the gold-tagged sand would have a settling velocityof approximately 25 centimeters per second. At this rate the packetswould reach the ocean bottom in water depths up to about 25 feet beforedissolving and releasing the sand to move under the influence of ambientforces on the bottom. Nevertheless, to ensure more rapid settling, thepackets were weighted with several lead pellets. Also, dissolving timecan be lengthened by using thicker plastic bags.

The use of sand tagged with gold, which has a higher energy gammaphoton than xenon, required design of another injection device by ORNLto effect safe and efficient handling. The dispensing device describedby ORNL (Case, et al., in preparation) is shown in Figure 4, rigged for-operation just prior to injecting the sand. The same container, withdifferent end plates, is used to ship the tagged sand by common carrierfrom Oak Ridge to the study site.

3. Detector and Onboard Data Collection System

No significant changes have been made to the towed ball-likedetector vehicle (Figure 5) as previously described (Acree, et al., 1969;

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The data acquisition system was modified slightly and now includeselectronic circuitry for collecting two channels of radiation data and

water depth (Figure 6). A high-speed, paper-tape punch was added topermit accumulation and punching of data on a 1-second basis. However,normal operationui mode was at 2-second intervals, i.e., every 2 secondsthe operating data channels are interrogated and read into the real-timedata display and putsch paper tape storage for later data h idling andanalysis. The syst,!mi development and modifications were accomplished bythe participating ORNL personnel and are detailed in reports by Acree,et al. (1969) and Case, et al. (in preparation).

The mix of gold 198-199 provides three gamma photon maxima: 80 kiloelectron volts and 0.4 million electron volts for gold 198, and 0.2 millionelectron volts for gold 199. Discriminator settings are selected so thatradiation Channel 1 sees the photon energy range from 80 kilo electronvolts to 0.6 million electron volts, and Channel 2 is focused on the 80kilo electron volts peak.

4. Computer Program

Radiation measurements are made continuously as the mobiledetector is towed along a beach, through the surf zone, or along theoffshore bottom. Interpretation of the detected radioactivity, in termsof speed and direction, and ultimately in volume of sand movement, dependsin large measure on making maps based on the collation and manipulationof data pertaining to position, observed radiation, and time.

Individual surveys generally last from 1,000 to 6,000 seconds (about16 to 100 minutes). As data from seven channels are accumulated every2 seconds during the course of field surveys, as many as 21,000 bits ofinforrmation may be collected. The only means of handling the data isby a computer. The basic CERC program, RAPLOT, which is written for aUNIVAC 1108, 64,000 memory computer, has undergone several modificationsto refine the data processing procedures and to provide more completeand useful printed and graphic output. Details of the RAPLOT II programand information of continued direction of program modification (RADCON)are presented by Turner (1970). An example of printed output is shown inFigure 7. Graphic output consists of maps drawn on an incremental plotter(Bcnson-Lehner Model 305) driven by RAPLOT II-generated data. Theseworking maps are the basis for those in Section III of this report. Workto improve data handling and analysis continues at CPRC, and at ORNL.

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Section ITI. FIELD TESTS

1. General Program Design

Field tests conducted during September-October 1968 were de-signed to determine zones of maximum sediment movement (velocity) ona real beach; impreve all aspects of the RIST operation over previousstudies; test the modified instrumentation and new hardware; comparerelative merits of utilizing sand tagC: s' with either xenon-133 orgold 198-199; and for the first time known to the author, attempt tosimultaneously trace sediment movement on the beach face, and in theinshore and offshore zones.

The beach near Surf, California, on Vandenberg Air Force Baseproperty, was selected for the test site (Figure 8). It is a relativelystraight, sandy beach, and the nearshore bottom is sandy to +30 feetmean L wer low water and beyond (Figure 9). To accomplish the severalobjectives, replicate experiments were designed using the two isotopes.In each instance, the packets of isotopically labeled sand were droppedst S-meter intervals along a line extending from the foreshore into thenearshore zone. Actual length of the injection line varied somewhat;this is explained later in this section.

As a backup to instrumental sensors, and wave-weather forecasts,visual observation cf littoral environmental factors were obtained usingthe methods described by Berg (1968) and Szuwalski (1970). These ob-sarvations, made at least twice daily, provided data on wind speed anddirection, tide, wave and breaker characteristics, littoral current andbeach slope. As a consequence of instrument sensor failures, dependencehad to be placed on the visual observations and the wave and weatherforecasts.

Radiation measurements are made continuously as the mobile detectorsystem is towed along the beach, through the surf zone, or along the off-shore bottom. Position of the LARC XV is determined directly by theCubic Autotape navigation system used; position of the radiation detec-tion vehicle is computed. The schematic diagram (Figure 10) illustrates

*a typical RIST survey, based upon the actual experimental operations atSurf. Data and placement of injection and isotope activity are suma-rized in Table I.

2. Xenon Experiments

On 25 September 1968, 36 1-liter packets of xenonated sand(specific activity 42.3 microcuries) were placed as a simulated lineinjection 590 feet (180 meters) long from 46 feet mean lower low waterto -6 feet mean lower low.water. The approximate position of theinjection along the range is shown on Figure 11 which represents con-ditions immediately following injection. Several surveys a day were

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$:4I +j ~ 0 . ~ 0

4))

Li-I +r- 4I V

.H 00

a) 0 - 00 0

U -4q 0

V)4 000

LI- 414)-4) 0 -4 0 V

0 0

V) 00 0

i7 .~

1 8

CORRECTEO COUNT R.TE .C/S)

E] S IX ocgrurx!4

/ /IM: 4 X otkotound

E3: 16 X kcgound:1> 16 X ockgroudr I

--6

0 0I

EXPLANATION A.

.------- Swvy Track Li.Dote 25 September : 1045-1101Apr-oximoe Injection Line, 25 September 1968

------ Approximote h Contours

.- k Aouima, Zone of Brving Waw. A-Appoximote Tide Line Ms 4u m - -

Figure 11. Pattern of xenonated sand immediately after release. Thedetector was operating and towed behind the LARC XV duringemplacement of the sand.

18

made through 28 September 1968, with patterns very similar to the patterndepicted by data collected in the morning of 26 September (Figure 12).On 28 September, a second line injection was made about 1,200 feet(635 meters) south. This line was about 672 feet (205 meters) long.Surveys following the second injection never positively identified theinjection, although tagged sand was still identifiable at the site ofthe first injection, probably because of burial. It is assumed thatsand injected during the second operation was rapidly transported down-coast (south) and dispersed below detectable limits. Littoral transportis summarized in Figure 13. Sea and swell are summarized in Figure 14.

Short cores of sediment were obtained along the injection rangeon 25, 26, and 28 September 1968 at varying elevations, but always onesample at mean lower low water. On 28 September, cores were also ob-tained 50 feet (15.2 meters) north and south of the first injectionline (Range 158) and along the second injection range (300 feet northof Range 159). Samples were removed from the cores at 2-inch intervals,and counts made. The energy spectrum was displayed during the countingoperation to ensure that xenon was present, especially where counts wereonly slightly above background. Some of these data are depicted in

Figure 15 which clearly indicates burial of tagged sand.

3. Results of Xenon Experiment

Patterns of sediment dispersal and burial depicted in Figures11-, 12, and 15 make conclusions concerning sediment Uovement tenuous,particularly since a count-rate balance is lacking. Based on theapproach of Bagnold (1947) and the ambient ocean waves and currentsif (summarized in Figures 12 and 13), the tagged sediment was expected tomove a considerable distance downcoast. But dispersal patterns indi-

cated only slight downcoast movement. Core data indicate burial, yetintuitively, nearly total burial seems untenable. An alternative pos-sibility is that movement of the tagged sand occurs, but in a ;mannerwhereby the particles stream off in a random pattern at a random rate.If this is the case, it is entirely possible that the streaming rate,coupled with the low specific activity level of the xenonated sand,

2moves particles downcoast at a rate below the level of detectabilityof the system.

The experiment in the CERC Shore Processes Test Basin (SPTB) in1968 indicated that a small quantity of high specific activity xenonatedsand would produce dispersal patterns similar to those of a larger quan-tity of low specific activity xenonated sand. Therefore, the subsequentfield experiment with gold-tagged sand - analogous to the high specificactivity xenon sand in the laboratory experiment - should provide someinsight into the reason for the observed xenon patterns. Assuming burialof the sed4,ment or no movement of the sediment, then the gold-tagged sandshould describe the same (or closely similar) pattern as that depictedby the xenonated sand. Conversely. if movement of xenon-tagged sand

19

CORRECTED COUNT RATE (C/S)

S~ I X Baowmn

5 16 X 6wkqpoued:

> 16 XBcgruw /-

, •

0440

-R-158

EXPLANATIONASwvey Ttock Lk, Oole 26 bept, ber : 0949-1006

- - Appromule Ir.jectin IiW, 23 September 1969-- 6- Apposiot Oepf Colon

I -........ ,.. ffmt Zan of Bkrg Woms WAU0 F

Figure 12. Pattern of xenonated sand approximately 24. hoursafter emplacement.

20

-7 - -

'1*~O

2LU t/30N/

Figure 13.* Littoral transport sumary, xenon experiments.Measured using dye placed in the inshore zone.Figure shows velocity and direction frominjection point.

21

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446

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22

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23

occurred, but at a rate and in a manner which was below detectabilitylevel, then wide dispersal of the gold-tagged sand would be noted.Results of the experiments using the gold-tagged sand indicate thexenonated sand did move.

4. Gold Experiments

On 4 October 1968; 24 packets containing about 14 cubic centi-meters of sand tagged with gold 198-199 specific activity 47 microcuries Jwere placed as a simulated line injection 426 feet (130 meters) longfrom -4 feet to -11 feet mean lower low water. The track of the vesselduring injection and conditions 2 hours after injection are shown inFigure 16; and 4 hours after injection in Figure 17. Dispersal of the

tagged sand from one injection line 23 hours after emplacement is shownin Figure 18. An hour after that survey, a second injection of gold-tagged sand was made 600 feet upcoast. In this operation 36 packets ofgold-tagged sand (specific activity 22 microcuries) were placed as aline 575 feet (175 meters) long from about +5 feet to about -6 feet meanlower low water. The precise path the LARC XV described during injectionprocedures is not known because of electronic problems. Due to wind andlongshore drift, the actual track was some distance downcoast (south) ofthe planned line along Range 158 illustrated on Figure 19, which alsoshows the dispersion of gold-tagged sand 2 and 26 hours after the secondand first gold injections, respectively. A subsequent survey on 5October is illustrated in Figure 20. Results of the final full-scalesurvey of this test 4 days later are shown in Figure 21. In total,although not all surveys aro illustrated here, 23 surveys of varyingduration and areal extent were conducted. The information from all plotswas used in drawing the maps in Figures 16 through 21. Lpngshore current,sea, and swell during the experiment are summarized in Figures 22 and 23.

Short cores of sediment were obtained along the injection range(R-158) at elevations from -6 feet to +6 feet mean lower lo': water onS, 7, 8 and 9 October. Cores were also obtained SO feet north and southof Range 158. No radioactivity was detected in the cores although surveysshowed tagged sand to be in the area. Lack of tagged particles in thecores is judged to be due to the small diameter of the core and the rela-tively few tagged grains which make the probability of coring tagged orradioactive grains very small.

As a result of burial, degradation of the higher energy photonsoccurs with enhancement of the lower energy peaks, in this instance 80kilo electron volts peak. Ratios of counts read in the two discriminate-radiation counting channels are a measure of burial, i.e., the largerthe number the deeper the sand is buried. It is not yet possible togive significance to burial depths indicated by the ratio, although thequalitative significance is useful. Ratios of corrected count rate arecomputed as follows:

R2RD K= 1 - K2

24$3

.. .... . . -. 1 -...- ' : = --

-.- 7 : ' . -* ' '

where

RD = burial depth ratio

R, = corrected count rate (c/s) in RAD Channel f

2 = corrected count rate (c/s) in RAD Channel 2

R1 and R2 represent an average of 10 readings. On the beach face, com-puted ratios indicate burial with time on the injection line. Laterallyalong the beach face, ratios indicate sand is nearer the surface asdistance from the injection line increases. Seaward of the surf zone,little lateral change in ratios was detected, although an increase -inratios occurred through time. Interpretation is that mixing to somedepth has occurred, rather than stratification with an overburden ofdead sand.

S. Results of Gold Experimersts

A comparison of maps showing the distribution of xenon- andgold-tagged sand (Figures 11 and 12, and 16 through 21) indicates dif-ferences in areal extent and possible interpretive differences. Somedifferences in grain size of tagged sand was noted in a previous sectionof this paper. As the size characteristics were still similar to theuntagged sand in the study area, no deleterious effects are judged tohave occurred because of tagging techniques. Tests at ORNL (Stephens,et al., 1969) indicate their tagging techniques fimly fix the radio-active gold to the grain surface. The maps are therefore judged torepresent dispersion of sand grains and not the dispersion of goldabraded or leached from the surface of sand grains.

Differences iq ocean conditions during the xenon and gold experimentsmight be the cause of the different patterns of movement suggested by themaps. However, during the first days of the gold experiment, sea, swell,and longshore currents were closely similar to those during the xenonexperiment. During 6, 7, and 8 October, wind and swell were considerablyhigher than any conditions encountered during the earlier xenon tests.

Gamma photons emitted by gold are much greater than xenon in energy(0.4 million electron volts versus 0.08 million electron volts). There-fore, they are more easily detected, even in smaller grain concentrations,than xenon-tagged sand. It is the consensus of the field-program partic-ipants that the data used in compiling rAps depicting movement of gold-tagged sand are real, and that for purposes of working in the oceanenvironment on a large scale, gold-tagged sand yields better informationthan sand labeled with xenon using present tagging techniques.

An experiment in the CERC SPTB to study littoral drift indicatedrapid alongshore movement at the landward edge of the breaker zone, and

Text resumes on page 34

25

5A-

! " - ._ -I,

-CORRECTED COUNT RATE (C/S)_...------------ -------

Fl 5 4 X ockqround -t4] 16 X 8ockground ' "

> 16 X ackground ------------------------------------------

, - - -- - - -- -

e% %

* . *,

-EXPLAN.ATION i - 6

------- Sur vey Trock Line, Date 4 Qclober: 1224 -1:30t; .......... Aplrx~Oim kt W ec Line, 4 October' iMe

,,z'.m°/ - 6-- Approxinote Depth Contos U*m.VA

R-1-6AIrlmt 55 * of '- n Wove

R-159 Aproime Tide Lin

.,,S. , S

I- •. , ' I-. I

Figure 16. Dispersal pattern of gold-tagged sand approxinmtely2 hours after injection.

26

* *

CORRECTED COUNT RAIE (C/S)

i'] <I X BockgowAd .

1; 4 X ockrod 'i5> 16 X Beckq~ue w "4".

> (6Xocko I ---

4~*. /A -" --- -------

,1.,. ..

I , .: ..

-------------- - "

Art SWi kk 6 Ln eW iQ

,- .-, .___ ,..-,..._ ...4-

A~~~ ~ ~ .4W~kDP c~

AWWA T LMi S

S~r~y ~it 41D6 44 M M 4"-'. .4 -4 . .. ,,

Figre 7.Dispersal pattern off gold-tagged sand approximatelyigurea17.4 hours after injection.

2?'

-iAs

"ICORRECTED COUNT RATE (C/S) ----

E] S Ia ockgrouruiS 4 XBackground .....

Sc 16 XIakrud1

> 16 X Background -2

0 4

6 + ~. 6

A _ EXPLANATION %

----- Survey Track Line, Dote 5 October: 0914-1008

- -- Approximate tnjectiw1 Line, 4 October 1968I -6s- Approximate Depth ContoursI :zc-~.2 Approximcfe Zone of Breaking WavesR-5

R-!59 - - Approximate Tide Line

4 ISCALE IN IIE[

Figure 18. Dispersal pattern of gold-tagged sand approximately 23 hoursafter injection. Note the rather abrupt upcoast (north)truncation of the pattern and the minor movement shoreward.

* 28

000

< VCU .

oo -J

I.tI

V I I A A

Coi 1:1 Ecc----- ----- -- CJ~

+

Figure 19. Dispersal pattern of gold-tagged sand 2 hours after theinjection of 5 October from approximately +6 feet to -6 feet MLLW600 feet upcoast of the earlier gold injection. Note very rapiddowncoast movement of tagged sand just inshore of the breaker zone.

-. - . 1 -

'.

-- x

+

-- ~~ ------

%n CI w

-J',,.7 '

Fgr CC"a

1ahet n 1k-

41' VII VI A!

C IO

K~-F ~ ~ +

4 0 0

* .0

.....- . ......

.........

... .. .. .

In

........... .. ...... --- ---- E........... ............... 4

.. .. . ...

........

.. ... . .. . .

.. .. . .. '

a -H

4j r4

Vr n

.. ........ C

N

+414

EMI

4 14Figure 22. Littoral drift summary, gold experiment.

Measured using dye placed in the inshorezone, data is velocity and direction frominj ection.

32I

N

RleJ2-3 Foi - E Sea

N

WZ?0-. - -. DJ2-3ft ) SeI

0.

S

Figure 23. Sea and swell summary, gold experiments. Height in feet anddirection from which the wave is approaching.

33

for a short distance seaward of the breaker zone (Taney, 1963). In a2-dimensional sense, several aspects of that model are analogous to thefield data. Core data, obtained at Surf, California, indicate fardeeper burial (maximum 1.2 feet) than the 0.10 foot reported for the Imodel, although it is not possible to make a scale comparison.

Little onshore-offshore movement was indicated during the fieldtest. Some onshore movement of the first injection of gold-tagged sandis indicated in Figures 16, 17, and 18. However, after the second in-jection, shoreward movement of the offshore sand was obscured by thevery rapid alongshore movement of the sand from the second injection.The survey made on 9 October indicates some seaward movement of taggedsand; high waves during 6, 7, and 8 October are judged the cause. Usingfluorescent grain3, Ingle (1266, page 189) found ". . . . in all cases,the majority of tracer grains traveled shoreward into the breaker zonealthough dispersion occurred in all directions". However, in Ingle'sstudy of sediment movement immediately seaward of the breaker zone, sandwas released 75 feet seaward of the breaker zone. During the RIST test,tagged sand was released along a line extending up to 350 feet bayondthe breaker zone. Later, however, as a result of a storm and subsequenthigh waves on 7 October, the most seaward release point was in the breakerzone. By analogy then, the tagged sand should have been moved shorewardto the beach. The Jata do not show that this occurred.

Downcoast (lateral) movement is very evident, and during the initialsurveys some slight upcoast movement of sand is evident, particularly onthe beach face. However, rather sharp upcoast truncation of tagged sandis on all maps; it was not expected, but has been found in other RISTtests in nearshore areas. Such patterns .appear to preclude the use ofsimple diffusion models to explain the dispersal of tagged grains.

Another point of interest is the location of zones of transportrelative to the breaker zone. All maps depicted indicate the zone ofbreaking waves during the time of survey. Because-of the tide and waveconditions, the seaward limit of breakers was at about -5 feet mean loverlow water for the first survey of S October (Figure 18), and at about-6 feet from then to 7 October when the limit moved to about -12 feet.Movement of sand seems to be i-estricted to the zone of peaking, breakingand translatory waves.

Data also reveal zonal differences in relative rate of longshoremovement. Survey data on 5 October (Figures 19 and 20) show that sedimentat the landward margin of the breaker zone moved alongshore in about 3hours the same, or greater, distance than that sediment seaward of thatzone moved in 26 hours. Sediment on the beach face moved slower thansediment in the inshore zone, but faster than that in the offshore zone(seaward of the surf zone). Survey data on 9 October (Figure 21) indi-cate that much of the tagged sediment previously present in the inshorezone had moved completely out of the survey area. Ratios of count rate

34

indicate burial at the updrift end of the radioactive mass; particlesreleased from these zones therefore would be few in number, and by down-drift dilution with untagged sand could escape detection. A relativerate of alongshore transport would be: inshore zone > beach face > off-shore zone seaward of peaking and breaking waves. Sea and swell duringthe October series of experiments are summarized in Figure 23.

Mathematical simulation studies presently underway as part of theRIST program tend to fit the data observed in the field (W. R. James,personal communication). The observed difference in transport velocityis in direct agreement with the model tests conducted by Taney (1963)and the results of field studies reported by Ingle (1966). Studies byKomar (1969), which were confined to the beach face, imply greatervelocity of sediment transport in the inshore zone than on the beachface.

In any sand-tracing experiment, knowledge of the depth and patternof sand burial is important; it is fundamental to quantify littoral trans-port. Courtois and Sauzay (1966) present several theoretical models that,in general, follow a parabolic law and assume mixing (contrary to strati-fication) of the tagged sand with untagged "dead" sand. However, ex-perimental results obtained in a later study (Courtois and Monaco, 1969)indicate burial offshore more closely follows an exponential law, andthat stratification exists. Komar's (1969) beach studies (using fluores-cent dyed sand) suggest an exponent'al type of burial law; that is, thedepth of burial decreases exponentially with downdrift distmice from thepoint of injection.

Short cores from the beach face obtained in this RIST experimentindicate stratification occurred, and tagged sand was overlain by deadsand. Core data is insufficient to contribute additional confirmationto the decrease in burial depth downdrift from a source. Ratios of thepeak heights of "the two radiation channels do tend to confirm a decreasein burial downdrift. Calibration of the detector system is still in-complete, so precise information about burial depth is still unknown.However, where count rate is of the same order of magnitude, computedratios indicate decreasing depth of burial on the beach face with in-creasing distance from the source. Offshore, seaward of the outer lineof breakers, the ratios are not significantly different, and this is nowinterpreted to mean little burial by "dead" sand, or at least shallowburial with mixing of tagged and untagged sand. Bed forms offshore inthis area are slight ripples of sand overlying a firm sand bottom andare consistent with such an interpretation. Partially destroyed largeripples (6 by 4 by 1 1/2 feet deep) were also observed in the zone from-16 feet mean lower low water to the limit of observations at -20 feetmean lower low water. Waves and currents creating those features wouldbe expected to cause deep burial and a consequent change in the radiationratios.

During February 1969, another.field test at Surf, California, w;sundertaken. The specific purpose was to obtain data on the pattern of

35

sediment transport during a different season and under different oceano-graphic climate. Long-range wave and weather forecasts indicated sea andswell conditions of 6 to 8 feet 90 percent of the time. These waves arewithin the operational range of the LARC XV mnphibious vehicle. Based Ion preliminary analysis of the earlier September-October data, two simul-taneous line injections of gold-tagged sand wore made along Range 158 indepths of 6 to 14 feet mean lower low water and 21 to 27 feet mean lowerlow water. Returning to shore after injection, the LARC XV developedmechanical problems which could ,-ut be repaired at sea nor on the beach.Tracing components had to be transferred to the backup LARC V. Sea andbieakers then rose to heights of 12 to 16 feet and stayed that high until

the field study was terminated several days later. These high waves pre-vented safe operation of the backup vehicle in the sea, and tracing wasconfined Io the beach. Tracing data indicated the tagged sand did notreturn to the beach.

Static tests with the mobile detector were conducted to determine,empirically, the ability of the system to detect burial based uponattenuation of gamma photons emitted by the gold. Small quantities oftagged sand were buried at 10-, 6-, and 3-inch depths and covered withdead sand. The spectrum obtained, readout and photographed at the site,is shown in Figure 24.

Section IV. COMPARISON OF TilE RIST SYSTEM WIT! OTIERARTIFICIAL TRACING METIIODS

1. General

Discussions of sediment tracing experiments invariably generatecomparisons of particular programs, or comparisons between specificaspects of particular programs. Kidson and Carr (1962) present an ex-cellent summary of methods used in marking beach sediments for tracingexperiments. The purpose of this section is to relate the RIST studyto other sediment-transport studies, to review reported transport-studymethods, and briefly describe their procedures and scope.

Artificial tracers may be grouped into two major categories: stableand radioactive. In either case, the tracers represent particle, thatare placed in an environment selected for study, and are used for rela-tively short-term studies of sediment dispersion. Stable particles con-sist of crushed colored glass, crushed bricks, and anything else that isunlike the natural sediment. Naturally occurring sedimentary material,painted or coated with a bright paint or fluorescent dye, has also beenused to study sediment transnort (Ingle, 1966; Stuiver and Purpura,1969). Activity mayv be induced in radioactive tracers in a number of,av's . Labeling may involve neutron activation of an element in a mineral;for example, phosplherus-32 prel)ared by this method was used with limitedsuccess on the California coast (inman and Chamberlain, 1959). Radio-active material has been placed in holes drilled in a large pebble. Iti,ts beer incorporated in molten gl Iss which, when hardened, is crushed

36

-U)

Ch0

4.1$4 4

0',4.0

.4

WV)

and resized (Sato, 1962; Taney, 1963). Radioactive material has beenplated on the surface as in the ORNL-developed gold technique utilizedin the RIST program. Radioactive gas (Kryptn 85 and Xenon 133) hasbeen absorbed into quartz sand (Chleck, ot al., 1963; Acre, et al.,1969).

While particular experiments employ specific sampling methods andoperational characteristics, there are basic elements in all tracingstudies. These are: (1) selection of a suitable tracer, (2) taggingthe particle, (3) placing the particle in the nvironment, and (4)detection of the particle, either in situ or in a laboratory afterremoval from the field location. For stable tracers, except in clearwater or on a beach at low tide, samples of the sediment must be removedfrom the envirenment before the particle can be accurately detected.Collection of the data requires physically counting or weighing thesediment grains. In either nuclide or nonnuclide tracing, the particularparticle must be detected. With fluorescent pigments, the detectionis nornally acccmplished by an ultraviolet lamp. Sensitivity of thistechnique is usually reported to be about 1 part in 10 million of thesample examined. However, results are very dependent on the extent towhich the field area being studied can be tampled. Sincb dilution ofthe tracer with natural sediment occurs rapidly, sampling is difficult.As a result, most studies using a fluorescent material are restricted toshort periods of several hours. Also the number of samples that can becollected and processed is limited because manual sampling and laboratoryanalysis are time consuming. An automated device for counting fluorescentparticles, described by Teleki (1967) apparently has not had widespreaduse.

When a radionuclide is used as the tracer, it is possible to detectit at tVe field site. The xenon-133 isotope-tagging technique was de-veloped specifically for the RIST program, and is totally new to thefiel. ' sediment tracing. Gold-198 has been used numerous times in thepast, especially in studies to determine the dispersal pattern of siltsand alays, Jiowever, the gold-tagging technique developed for RIST(Stephens, et al., 1969) is greatly improved since the tag is firmlyfixed to the grain so that detection of the isotope definitely showsthat a tagged sediment particle has been detected. The same statementcannot be made with assurance for the previous gold-tagging techniques.In all studies reported, a sled device was used to carry the radiationdetector over the bottom of the water body. Detectors are Geiger-Willertube or scintillation crystals. The collected data are on a continuousstrip chart, although in some cases digital printout has been used(Hart, 1969; Courtois and Monaco, 1969). The field technique for locat-ing the position of the detector sled, or more specifically, the vesseltowing the sled, has been by the usual surveying technique, when on agiven signal, two men operating surveying instruments read an angle ofsight to the vessel. This information is recorded and later draftedby hand.

36

2. Comparison of RIST to Other Sediment Transpcrt Studies

(a) Radionuclide Systems. In addition to investigation in theUnited States, radionuclide tracing technology is actively pursued bythe French, Japanese, British, and Australians. Rather than review allof the reported st'dies, representative studies have been selected foxdescription and consequent comparison to the RIST program.

Perhaps the best known of the British studies wat. reported 1sCrickmore and Lean (1962). This study was carried out in laboratoryflumes with the goal of modeling sediment movement and providing aformula for quantifying results. G6iger-Willer tubes, buried in theflume, were used to detect radioactive sand moving in ripples over thedetectors. Results of the studies are presented as a formula whichprovides the quantity of sediment moving as deduced by the time-integration method.

Studies by the French (Courtois and Monaco, 1969) are similar tothe field programs of the British, Australians, and Japanese. Thesegenerally involve a sled-type detector carrying one or two scintillationdetectors. In the French program, the sled carried two scintillationdetectors with a sensitivity of 1 microcurie per square meter. Sandgrains were tagged by the adsorption and consequent oxidation ofchromitm-S1 on the surface of the grains; 10 pounds of sand were taggedwith a total of IC curies. Radiation was recorded on a strip chartand later by digital printout. Tha test was carried out on the Frenchediterranean Coast in water 12 to 15 feet deep. All surveys of sedi-

ment dispersion from a point source were seaward of the breaker zone.Location of the vessels 6tring the surveys was obtained by the cutoffangle technique described previously; angles were determined at 1-minuteintervals. No information is provided with regard u the number ofprofiles o( the length of time involved in each survey; however, thecontoured area covers a rectangle 360 by 1,200 feet. Three surveys wereconducted over a period of I month. Qualitative and quantitative resultsof the study are reported. Qualitative results are provided by a mapwich shows the dispersion of the tagged material during the survey.A quantitative analysis of the survey was made- by using a radiation-material balance to determine depte of burial (correlated with some coredata) which was then coupled to the displacement of the computed centerof gravity of the moving mass of tagged sand.

The U. S. Army Engineer Waterways Experi t Station (WES) atVicksburg, Mississippi, recently completed a survey in the Houston ShipChannel (Hart, 1969). This study in the Galveston, Texas, area is themost recent research in fediment tracing reported by WES and is one ofthe most up-to-&te of the radionuclide tracer studies in the UnitedStates. It is also representative of several previous WES programs.The isotope reported used was gold-198 which was mixed in solution withsediment at the site. Tagging occurred by simple 3dsorption by fine-grained sands. About 4 cubic feet of sediment were treated with a total

39

i

4

radioactivity of 4 curies; the tagging efficiency was not reported. Thesurvey was essentially a zigzag pattern in the ship channel, and covereda track about 1,000 feet wide and 8 miles long. The detector vehiclewas a sled that carried one scintillation counter with a sensitivity of6,000 counts per minute per microcurie per square foot. Radioactivitywas recorded on an nalog strip chart; counts were accumulated over a10-second period. Location of the towing vehicle was determined by thecutoff angle technique at 2-minute intervals. The experiment lasted 1 week;one survey was made each day. Method of data reduction is not stated, butit is assumed to be essentially by manual computation. Results - onlyqualitative - are shown as a diagram indicating the presence and level ofradioactivity versus distance along the channel. Other WES programs ofthis type have been conducted in San Francisco Bay, The Galveston areaand in Charleston, South Carolina.

(b) Fluorescent Systems. In the United States more studiesusing fluorescent dyes have been reported than those using radioisotopes.Although most studies are at beaches, some have been made of rivertransport.

The United States Geological Survey (USGS) recently prepared anopen-file report on sediment discharge at Clear Creek, Colorado (Kennedyand Kouba, 1968). In this investigation, dyed sand was introduced at aconstant rate at a point for a period of 28 hems. Samples were obtainedfrom a point near the stream bed 1/2 mile downstream. In this USGS study,three fractions of different sizes of the sand carried by the river weredyed with different colored fluorescent material. Daring the experiment,0.2 pound (90 grams) of each size fraction were injected every 3 minutesfor ?8 hours. About 300 pounds of sand wpre used. The stream was sam-pled continuously during the test. Samples were dried and sieved. Eachsize fraction was placed in a vibrating-feeder device with a spiraltrough, and observed under ultra--violet light so that the number offluorescent grains could be recbrded with a manual counting device.Results of the program are quantitative, based on the Crickmore andLean constant-injection technique.

At the University of Florida, the Department of Coasta! and ;,ceano-graphic Engineering has been experimenting with fluorescent tracing inthe marip, environment for several years. In their beach studies, theexperiments have generally been carried out between the high- and low-tideline. In a recent study (Stuiver and Purpura, 1969), material wa in-jected as a band 50 feet wide from the high-tide line to the low-tideline with additional sand placed in water-soluble bags to a 3-foot depth.Samples were obtained along ranges spaced 500 feet apart; three sampleswere collected along each range. After the samples dried, they were splitinto 100-gram parts which were then counted to give the concentration offluorescent particles as the function of distance from the injection line.The experiment lasted about 45 days, and samples of tagged sand wereobtained as far as 5,000 feet downcoast. In addition to the studiesat the beach, the University of Florida scientists studied sediment

40

dispersion at an inlet. In this study, 2,000 pounds each of 4 colo~r ofdyed sand were used. The study area was sampled periodically for about1 month with samples obtained along ranges spaced at 100-foot intervals.Results of both of these studies were qualitative only.

Recently, the Scripps Institute of Oceanography (Komar, 1969) re-ported the results of using fluorescent tracers through three beaches,two of which were in Southern California. In general the area studiedextends from the plus 3-foot contour to the minus 3-foot contour, withsand injected as a band of sediment raked into the beach face at lowtide. Where the sand had to be placed through the water column, the sandwas packaged in paper bags; these were manually broken open after place-ment on the bottom. Between 70 to 200 samples were recovered from an areaabout 200 by 1,000 feet; 100 to 200 pounds of sand were used. Resultswere expressed as maps showing number of grains of tracer per kilogram.Volume samples (grab) were obtained rather than surface samples (greasedcard), usually obtained in fluorescent studies. In the results reported,samples were usually obtained only once for each test. At Silver StrandBeach (south of San Diego) five tests were ronducted. The maximumelapsed time from tracer injection to sampling and conclusion of thesurvey was 4 1/2 hours; usual duration was 1 hour. Results expressed arequalitative and quantitative. However, the quantity of sand moving mustbe considered a minimum because the maps resulting from the study showmarked truncation at the seaward limits of the sample zone with indica-tions that maximum transport occurs seaward of the low-tide line. TheRIST study has confirmed that the maximum velocity of transport is in theinshore zone, not on the submerged foreshore.

Perhaps the most widely known and most often quoted work on fluores-cent tracers is that by James C. :ngle (1966). In his research, Ingleinvestigated five Califoiia beaches; the areal extent studied was aboutthe same in all cases. At Trancas Beach, west of Los Angeles, sampleswere collected as much as 3 hours after injection of the tracer; this wasthe longest study. In all studies, packets of tagged sand were placed atspecific intervals along a line seaward from thf beach backshore. AtTrancas, six packets of sand weighing 5 pounds each were placed at 25-footintervals along the line from mean sea level to a depth contour of 4 feetbelow mean lower low water. In all, only 57 data points were sampled overa rectangular area 200 by 850 feet; a total area of 170,000 square feet.The 57 data points, each represented by a 9-square inch sample (3- by 3-inch greased card) cover a total area of 3.56 square feet. This sampledarea represents 0.000021 of the total area on which to base contours ofgrain count.

In the following paragraphs, data on the test at Surf, Californiain October 1968 are used for a comxarison with of the studies brieflyreviewed above. On 4 October 1968, in a period of 44 minutes, an area900 by 1,300 feet (more than 1 million square feet) was surveyed. Thesurvey started 2 hours after injection of the isotope, and extended from"the p]:,s 3-foot contouz to about the minus 15-foot con-our. In the course

41

of the study, 1,300 data points (collected at 2-second intervals) wereanalyzed; and about 20,000 square feet (10,000 feet of track times a2-foot width visible to detector), or .017 of the area mapped, wereactually sampled. On 9 October (Figure 20), a rectangular area 3,300by 1,600 feet (in excess of 5 million square feet) was surveyed in lessthan 2 hours - 126 hours after injection of the isotope. The surveyextended from +6 feet on the beach to -15 feet seaward of the surf zone.All told, 3,000 data points were collected over a track nearly 20,000feet long. That track length represents examination of nearly 40,000square feet of the area represented by the map or about 0.0075 of thetotal area. A more significant comparison of the RIST data and thatof Ingle's study is illustrated on Figure 25. The paper by Courtoisand Monaco (1969) does not indicate the number of data points, but thedimensions of the dispersing mass of sand can be determined from themaps illustrated. For comparison purposes the larger pattern is alsoillustrated on Figure 25.

A search of literature shows no other studies have synopticallyexamined the beach face, inshore zone, and the offshore bottom. Otherreported studies are confined to a beach face or deep water (a harbor,a bay. or the ocean seaward of the surf zone). The earlier inability tolook at the inshore zone, the zone of maximum transport, has been due tothe detection vehicles and detector systems that were not rugged enoughto withstand the extreme forces of the surf zonc. The ball-type detectordeveloped for RIST solves this problem. However, the general techniqueof towing the detector vehicle over the sediment-water interface wheresediment transport is taking place is common between the RIST system andother radioisotope tracer systems. Use of a 4-detector array provides ahigh degree of sensitivity, increases detection capability, and examinesa larger area, and thus improves the counting statistics. The RIST dataacquisition system, which automatically collects and correlates time,position, and radiation counts, is unique in the field of sedimenttracing.

Section V. SUMMARY

Studies carried out at Surf, California, indicate the suitabilityof the techniques and technology developed in the RIST program for simul-taneously tracing sediment on a sand beach, through the surf zone, and tothe offshore bottom beyond. Sand labeled with the radioisotope of gold198-199 provides much more data for analysis of sediment movement thandoes sand labeled with xenon-133. In respect to collected data, gold isconsidered to be superior to xenonated sand for field tracing purposes.Use of a multiple-photon isotope, such as the mix gold 198-199, coupledwith a data collection system capable of discriminating between specificspectral levels, makes it possible to determine relative depths of burial,provided labeled sand is overlair. by "dead" sand.

Surveys conducted confirm that, in response to any given set ofwave conditions, a very diffcrent rate of sediment movement occurs in

42

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the zones between the high-tide line and -15 feet mean lower low water.Because of these differences, tracing surveys confined solely to theforeshore or offshore zone produce data only partially indicative oftransport in the zone of immediate concern to coastal engineers. Theindicated differing rates of transport, coupled with different depthsoi sediment mov¢ement, add complexities to the realistic determinationof quantities of sediment movement. Observed patterns of sediment move-ment indicate that previously used methods for solving the problem ofvolume sediment transport, such as displacement of the center of gravityof the tagged mass, simple dispersion models and random walk models, arenot adequate. While an accurate determination of sediment drift volumeremaips illusive, qualitative data on sediment movement useful forengineering purposes can be obtained on a scale heretofore unattainable.Data obtained with the RIST system can be treated as synoptic observa-tions of sediment transport in several adjacent environments. Qualita-tive sediment transport data of the type now possible to obtain throughRIST have application in the studies of such engineering works as:(1) the behavior of a groin; (2) the functioning of a "weir-jetty",and (3) shoaling harbors.

Research and development toward improving the RIST program continue,including improvement of data handling programs, quantification of driftmeasurements, and field tests on other sites. All are designed to makethe system a more efficient engineering and research tool.

44

LITERATURE CITED

Acree, E. H., Case, F. N., Cutshall, N. H., and Brashear, H. R. (1969)"Radioisotopic Sand Tracer Study (RIST) Status Report for May 1966-April 1968", ORNL-4341, Contract No. W-7405-eng-26. Oak RidgeNational Laboratory, operated by Union Carbide Corporation for theU. S. Atomic Energy Commission.

* Bagnold, R. A. (1947), "Sand Movement by Waves: Some Small-Scale Experi-ments with Sand of Very Low Density", Journ , Institute of CiviZEngineers, London, Paper 5554, pp. 447-469.

Berg, D. W. (1968), "Systematic Collection of Beach Data", Proceedings ofthe ttth Conference on CoastaZ Engineering, American Societyj of CivilEngineers, p. 273-297.

Chleck, D., Maehl, R., Curihiara, 0., and Caunrevale, E. H. (1963),"Radioactive Kryptoates", International Journal of Applied Radiationand Isotopes, Vol. 14, pp. 581-610.

Courtois, G. and Monaco, A. (1969), "Radioactive Methods for the Quanti-tative Determination of Coastal Drift Rate", Marine Geology, Vol. 7,pp. 183-206.

Courtois, G and Suazay, G. (1966), "Count Rate Balance Methods UsingRadioactive Tracers for Measuring Seciment Mass Flows", HouiZleBZanche 3: 279-290.

Crickmoure, R. J. and G. H. Lean (1962), "The Measurement of Sand Transportby Means of Radioactive Tracers", frooeedtnge, Royal Society (London)A266:40221, 1962, Nuclear Science Abstract 16:16588, 1962.

Cummins, R. S. (1964), "Radioactive Sediment Tracer Tests, Cape Fear River,North Carolina", Miscellaneous Paper No. 2-649, May 1964, U. S. ArmyEngineer Waterways Experiment Station, CE, Vicksburg, Mississippi.

Duane, D. B. and Judge, C. W. (1969), "Radioisotopic Sand Tracer Study,Point Conception, California, Preliminary Report on Accomplishments,July 1966 - June 1968", U. S. Army Coastal Engineering ResearchCenter, Miscellaneous Paper 2-69.

Hart, E. D. (1969), "Radioactive Sediment Tracer Tests, Houston ShipChannel, Houston, Texas", U.S. Army Engineer Waterways ExperimentStation H-69-2, pp. 1-14.

Ingle, J. C. Jr. (1966), The Movament of Beach Sand, Elsevier PublishingCo., Amsterdam, HollanO.

Ingram, L. F., Cmmins, R. S3. and Simons, H. B. (1965), "RadioactiveSediment Tracer Tests Near the Porth and South Jetties, GalvestonHarbor Entrance", U. S. Aroy Engineer Waterways Experiment Station,Miscellaneous Paper No. 2-472.

45

Inman, D, L. and Chaberlain, J. K. (1959), "Tracing Beach Sand Movement

with Irradiated Quartz", Journal of GeophyeicaZ Reearch, Vol. 64,No. 1, pp. 41-47.

Kennedy, V. C, and Kouba, D. L. (1968), "Fluorescent Sand as a Tracer ofFluvial Sediment". U.S. Geological Survey open-file report, 53 pp.

Kidson, C. and Carr, A. P. (1962), "Beach Materials for Tracing Experi-ments", JournaZ of the Hydrauio Division, Amerioa Society ofCivil Engineer., Vol. 88, No. HY4, pp. 43-60.

Komar, P. D. (1969), "The Longshore Transport of Sand in Beaches", ScrippsInstitute of Oceanography, Ph. D. dissertation, 143 pp. (unmublished)

WcArthur, D. S. (1969), "Sand Movement in Relation to Beach Topography",Coastal Studies Institute, Louisiana State University, T.R. No. 67,26 pp.

Pirie, R. G. (1965), "Sediment Rate of Granule- and Pebble-sized Clasts",Proceeding. 8th Conference on Great Lakes Refeeaoh, Pub. No. 13,Great Lakes Research Division, University of Michigan, pp. 232-239.

Sato, S., Takeshi, I., and Tanaka, N. (1962), "A Study of Critical Depthand Mode of Sand Movement Using Radioactive Glass Sand", Proceedingsof the 8th Conference on Coastal Engineemng, Council on WaveResearch, U;diversity of California, Berkeley. pp. 304-323.

Stephens, N. H., Acree, E. H. and Case, F. N. (1968), "Evaluation of FourMethods using Gold-198 for Surface Labeling Sand and a New Techniquefor Simulating Mass Labeling", Oak Ridge National Laboratory ReportORNL-4338, p. 9.

Stuiver, M. and Purpura, J. A. (1968), "Application of Fluorescent CoastalSand in Littoral Drift and Inlet Studies", Proceedings, 22th Confer-ence on Coastal Engineering, American Society of Civi Bnineers,pp. 307321.

Szuwalski, A. (1970), "Littoral Environment Observation Program irt Cali-fornia, Prelminary Report, !,ebruary-Deceaber 1968', U. S. ArmyCoastal Engineering Research Center, Miscellaneous Paper 2-70,

Taney, N. E. (1963), "Laboratory Applications of Radioisotopic Tracers toFollow Beach Sediments", Proceedings of the 8th Conferenoe.,on CoastatEngineering, Council on Wavc Research, University of California,Berkeley, pp. 279-303.

Teleki, P. G. (1967), "Automatic Analysis of Tracer Sand", Journal ofSedimentarj Petrology, Vol. 37, pp. 749-759.

Tz rner, P. A. (1970), "RAPLOT, A Computer Program for Processing andGraphical Display of Radioisotopic Sand Tracer Data", U. S. ArmyCoastal Engineering Research Center, M4isce~laneous Paper 3-70.

46

UNCLASSFIF ,,DbIt,,t Clamssicatl~ , ,,,

DOCUMENT CONTROL DATA. R & DSetwi Clieallkuti..O fe H889. ebef foec sf a lOWde ln omwleet mea be eatied * 0 owH so" sole 5. 8*a9e

I. ORl51iATING ACTIVITY (CeefpIeauah RePrIr SECURITY CLASSI6IMATtON ICoastal Engineering Research Center (CERC) iUNCLASSIFIEDCorps of Engineers, Department of the Army 86. GROUPWashington, D. C. 20016 •

3. NRPORT TITL

Et

TRACING SAND MOVEMENT IN ThE LITTORAL ZONE: PROGRESS IN TIHE RADIOISOTOPIC SANDTRACER (RIST) STUDY - July 1968-February 1969

4. OESCRIPTIVE NOTES (1n peo .1 A" -ac/elta. defs)

S. AUTHORISI (F rfe iA. 01d'0N 9l088, 8ies agod)

David B. Duane

.. REPORT DATE 7" TOTAL NO. OF PAES

August_1970 52_________

mL. CONTRACT OR GRANT NO. 900. OAIGINATORS REPORT NUEIECR.-

AT(49-1l)-2988 between Atomic Energy&PROJECT NO. Commission and Coastal Miscellaneous Paper 4-70

Engrg Research Center

A. OTHER REPORT NOISS (At *1 160 m A .a0O be e0edpd

;. fe 1114UTION STATEMENT

This document has been approved for public release and sale; its distributionis unlimited.

IS. SUPPLEMENTARY NOTES a. SPONSORING LITARY ACTIVITY

it. AD&TRACT

.Tagging procedures, instrumentation, field surveys and data handling techniqueshave been developed by the radioisotopic sand tracing study for the collection andanalysis of over 12,000 bits of information per hour over a survey track of aboutJ8,000 feet. Data obtained can be considered as nearly synoptic observations ofsediment txansport in a single environmental zone or in adjacent beach, surf andoffshore zones. Experiments at Surf, Point Conception, Point Mugu, and Oceanside,California, used sand tagged with isotopes of xenon or gold. Data from studies inbeach areas unmodified by littoral barriers indicate that the alongshore velocityof sediment transport differs from zone to zone. Transport seaward of peaking,breaking waves is less than transport on the beach face which is less than transportin the plunge and surf zone. Zone dimensions change with waves and tides. Tracingsurveys confined to the foreshore or offshore zones produce data only partly in-dicative of transport in the zone of immediate concern to coastal engineers. Studiesconducted at the site of shore structures indicate the RIST system can provide datauseful in understanding the effect of such structures ca sediment transport.

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Sediment analysesIlydrographic surveysRadioisotopesXenon- 135Gold 198-199Radiation detectorCesium iodide crystalsAutomatic Data ProcessingHleadlands

BeachesCalifornia

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UNCLASSIFIED


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