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~- 89 - . . . Exhibit E _ . . . . . . . . . , , v S=I~ON SrI13DI~ BY I~ SOIL CONS13RY~ON S3~VIC~' 1939 - 1940 earl B. Brown Soil Conservation Service Washington, D. C. . . . . The current sedimentation investigations of the Soil Gonsewation Service consist of (1) the research studies of the Sedimentation Div~- sion' Office of Research, and ( 2) the sedimentation surveys in designated 'watersheds conducted wail the tech Abidance of the S~d3;mentation. ;D,~ision under the administrative direction of the Flood Cont=1 Section of The Project Plus Division of the Service. These flood-control surveys are rJ Lad e jointly by the Soil Conservation Service, Forest' . . . . . . . Service' and Bureau of Agricultural Economics under the authority of Public No. 738,^ 74th Congress, which directs that "~nvesti~;ations of water sheds and measures; for run-off and mat erfiow retardation and sol ~ erosion preventio:n on watersheds shall be under the jurisd~ct~on:of and . . . . shall be prosecuted by the Department of Agriculture under the direction of the Secretary- of AgricUlture.'t ; · . . .. . ..-. Me general lines of activity of the Sedimentation Division (formerly Section of Sedimentation Studies, Division of Research) were described in the reports of the Committee on Sedimentation I°or 1956-ig37 (Appendix A); and 1957-1958 (~hppendix F). Me work of the Division is sub divided under four Secti ons covering respectively ( 1 ) ~ reservoir sed~nen;tation stuaiesj ~23'stre&= any varied sedimentation ;stud~es, (3) stream-load transportation studies conducted on natural siren principally at ~ station at Greenville, S. C., and ;~4) laboratory nvestigatio:n~ of sediment tr~sp;ortat~on conducted cooperatively with the ~alifor:nia Institute of Technology, Pasadena, Call t. : .. ,. ; . .... . . .. . .. . .. Prior to 1939 a large part of the activities of the Reservoir and Strew arid Valley Sections consisted of engineering surveys am su~?plehent6:~y geological studies of existing sedimentation conditions. This was necessary at first in order to establish a quantitative basis for dete:~n;ing the Are ai5:il ret o of sedimentation under present watershed conditions. Since the inaugurat~o:n of Flood Control Surveys, Wllich required much tlie same type of quantitative survey data, the Sedimentation Divisidn has ttmsterred most of its engineering survey work to the flood control survey organization. .. . . , . . . .. . . . - : ; The present personal of the Reservoir and Streisand lTalley Sections have dwoted ~ large patt of their Lime during the patst two years to developing techniques for, and assisting in the organization of,
~itit I: . -- 90 ~- and the analysis of data from, s.edimentat~ on phases of the Flood Control Surveys. At present (June 1, lg4O) ~ survey parties of 5 men each and approximately ~ dozen geologists are engaged full time on sedimentation studies Qua the flood control surveys* me two field sections of the Sedimentation Division now ,~.~e lS tochn~ca1 Hen. In the past tow ~years the close re.lati onshore of sod~mentat' en to problems of flood control ~ ~ several sections of Me country has boon adequately demonstrated,- and the practical importance fit sed~n~entat~on -investigations in the development of national policies and plans for flood control ma conservat' on has become more fully reco~;nized. Bone of these relationships =e pointed out here. The cowt~ction of f~ood~control acid multiple-purpose reservoirs constitutes one of the largest classes of public works in recent yams. The aggregate investment made or obligated for this purpose in the last decade, mainly by the Fe dorm Gove~ont, is not less than half a billion dollars. As the true value of these dewed cements must be measured not by the original cost but in terms of the ultimate worth of' the, dam sites thus utilized, it is apparent that ~ reasonably accurate prediction of the manner and ret o of storage depletion by sedunontat~on in those reservoirs is ~ matter of Cited concern. this lS true not only With res~?cct to the prior selection of tho Bite,, design, and reamer cop operations, but also in determining the extent of soil e~osion~con-trol regulated in the.~atershed once the reservoir ~s built. :I?our methods, separately or in combination, furnish possible awns of predicting the rate of silting of a new or proposed reservoir. Chose are (1} sapling the suspended load of the stream on which the reservoir is to be located, (2) measuring the sediment accumulation in existing reser- voirs having watersheds of si,~ni~ar character, (5) raeasuri~ the sediment accumulation on valley flood plains and in stream channels, usuallyin conjunction with the first or fourth method, and (4) moasuri~ the soil erosion by appropriate surveys of the watershed. Sump ended-load sampling has three disadYa~ta,:;es: (1) 7,'~th the exception of the Colorado Diver and Do Grand e no stream in the United States have been systematically sampled for ~ longer period than five years. As flood-control or other planning surveys are ordinarily complet- ed within two years from their authorization, ~t is seldom possible to obtain a record win ch satisfactorily represents a lox~-t~-e average. Analysis of 12- and 13-year records on the Rio Grande and Colorado shows that the largest annual Deduct load was 1,139 percent ma .'B54 percent more than the minimum annual load, respectively, for these streams. (2) Where ~ appreciable part of the sent is tra:as?~orted as bed load, a factor of error is introduced which thus far has been impossible to evaluate correctly. (3) Properly conducted suspended-load sampling s costly' even for relatively short periods.
__ 9~ __ ~cl~ibit _ Measurement of the sediment volume accumulated over ~a. period of years tin existing reservoirs gives, with certain correct' any, a basis; for determining the average.a~1 sediment:production per unit of area from a watershed of given physical and :~=d-use Characteristics. The measured sediment includes both bed load and suspended load. Factors that moist be considered in applying such data to other reservoirs fall: in two classes, which relate (~) to the degree of Similarity of water- .shed characteristics, and (2) to [actors affecting measurement of total sediment load in the existing reservoir ma to the depositiona1 charac-terist' cs the serge load would assuage in ~ proposed reservoir. Conaideri~ only the second class, three conditions need to be taken into account: (1) Me Percentage of tote sediment from the vatersI~ed which passes completely through the reservoir, and must therefore be estimato-d separately varies greatly, depending upon such factors as the relation Cal storage capacity to watershed area, the shape of the reservoir, the caner of operation of the den, and the character of sediment. (2) The amount of sediment that will be deposited above the reservoir as the top-set beds of the reservoir delta Id must be added, after measurement, to the reservoir accumulation depends on the topography of the valley above the head bf the reservoir and on the character of the stream load. (5) Lee volu~ne-we~;ht relations of the sediment, as deposited and as altered by tinge, to the total stream load and to the soils and other sediment sources in the watershed. For . .. . example, 1,000 acre-teet of sediment r.easured in a given reservoir may have a dry weight of 40 pounds per measured cubic foot, whereas at its source, as soil, it weighed 80 pounds per cubic foot And comprised only 500 acre-~et. However, ero:;~or~ of 500 acres of soil from the same sources may have a weight of 60 pounds per cubic foot in another type of resorro'~ because (1) the second reservoir, if for example used for flood control, may be dry each reason allowi:n~; compac- t~on of the sed:i~Qent or (2) because of sorting in the course of stream tran~porta:tion or within the reservoir the average texture and hence the ~rolume-weight relations of the deposited part of the 500 acre-sect of erosional debris may be d~ere:E~t than in the first reservoir. . Quantitative measurements of modern sedamm:t in alluvial valleys have been; made successfully in Gracious places in the United States. Such measurements in combination with suspended-load records or erosion surveys Ernest a basis for estimated :~ore closely than may otherwise be possible the rate of sedimentation in a proposed reservoir. This method is particularly applicable where the reservoir basin covers a relatively large part of the valley lands on which deposition is occurring within a watershed, or valley Ends on which deposition is occurring rapidly and includes. a considerable [faction of the fatal sediment coming into the reservoir area. This method has recontI'.r been used in estimating the rate of silting; in the Sardis Flood-Control Reservoir in the Little Tatlahatchie watershed of northern D.~lississippi.
~hibit E -- 92 -- Discussion of the purpose and methods of erosion surely of watersheds is beyond the scope of this paper. It is perhaps suffici ent to state that from the standpoint of volumetric measurements those now cc'~npleted have been found to reflect more the movement of erosional debris within a watershed, often for Very short distances, than the amount ~ . Of material which has been transported out of a drainage basin. However. the large Closet of basic data being collected and delineated in survey, of soil, slope, 1 end use, and degree of erosion may at some :Outure time, with perhaps supplementary field studies, procure Screwy useful in volumetric calculat i ons . The stream- arid valley-$ediment problems Countered in connection Ninth flood-control surveys have been of four major types, (~) damage to alluvial soils bar deposition of relatively coarse and i~erti~e sediment, (2) dodge to highways and railways by sediment accumulation on them, or lathe ditches requiredformaintene.nceof theroadbed, (3) damage end Crease flood hazards caused by filling of stream channels or drainage aid irrigation ditches, and (4) increasing flood hazards and flood damages due to lo as of capacity for overbank flood discharge below the l~el of terrace lands or other relatively valuable or highly improved properties, as a result of aggradation of lower flood-plain surfaces, For conven- ienc<3 in fiend surveys, the sedimentation investigations have also frequently been extended to cover problem of flood damage by scouring of relatively fertile top soil from alluvial lands, or by destruction of alluvial ~ ends by stream-bank erosion. In the research field, as distinct Prom flood-control surveys, a technical bulletin (9) entitled, "Some Principles of Accelerated Stream and Cables' Sedimentationt' was completed during the year and is in press as this Is written. This bulletin sun~a~izes the results of detailed studies in ~ small part of the Tal~ahatchie River drainage basin, north-c<3ntral Missy ssinpi, and presents 45 '"principles" based on these and other less intensive studies in various areas of excessive diluvial sed~entat~on. The ~SSi$S1ppi investigations revealed tat the greatest part of the sediment delivered to the valley system from accelerated upland sol 1 ero sion has apparently been accumulated In the upper parts of the minor valleys, generally within ten miles or so of the point of origin, and that sand derived arose griller erosion has apparently caused more valley damage than the larger quantities of silt derided chiefly from upland sheet erosion. On the basis of studies In various parts of the country, ~ new s~.ster.` of genetic classification of valley sediment is proposed. Ire 45 principles are presented, sub- ject to revision as more information becomes availabl e, as statements Has described in a series of Depar=ont of Agriculture reports, an exer.:ple of which ~ s "boon and Related Land Uso Conditions on the Watershed of Quito Rock Reservoir now Dallas, Texas," by Richard dust. :.;arshall and Carl B. Brown, 1939.
__ 93 -- Inhibit of fact designed to focus attention on factors of major concem in the understanding of the relation between soil erosion and stream and valley sedimentation, and on the nature and importance of various kinds of dense found to occur as a result of accelerated rates of sedimentation. The scope of these principles is indicated by the following list of' sub-head~;s, under which they are grouped: Sig:L~fica:ace of criteria for recognition of modern valley sediments; notional processes as [actors ~n excessive sedimentation; Valley sedimentation as a measure of upland erosion; Damages resulting from culturally accelerated valley sedimentation; Inculcations of future trends in str~ and Maloney sed,unentation; Relation of strew and valley sedimentation to flood- control problems; and Relation of sedimentation conliro1 to soil conserva- ti on. Stream and valley sedirner~tation research was canting during the year in several representative secti ons of the upper Mississippi Valley and in the South Carolina Piedmont, and further progress was made on office Ad laboratory studies previously undertaken ~n connects on with a study of sedimentation in -the l.siddle :E~o Or and e Valley, New Mexi co . the study of str~ transportation of sediment load at a station on the Enoree :River near Greenville, S. C., has been described in an article by Dobson and Johnson (5~2 during the year. ~ continuous record of bed load, suspended load, dissolved load, and discha:r~;e has been maintained at this station since January 1, 1939. Textural analyses have been made of the sediment and graphs have been prepared showing the movement of total sediment load by particle sizes. IsoLyetal maps shower hourly precipitation on the 64.4-sq.uar`3-mi1e watershed have been prepared from records of 13 recording rain gaffes within or immediately adjacent to the watershed. ~ representative station record for :February 1939, given in the above article, showed: P~n:fall 9.6 inches, :run-off 3.9 inches, .. ma:~:irm3m din scharge 1,200 second-feet, load ~:neesured by suspended-load saxapli~ 6,410 tolls, additional load measured by parting from the bed of the river (equivalent, undo the general conception of the meaning of this te~, to bed load, or the load below the practical level of suspended-load sampling 174 tons, and average dissolved Scat 71 ram. A useful by-product of the Apogee statio:E~ has been the development of the Anderson~:3instein sampler Huh pO=Q1tS silul~neous measur=.lent of current velocity and collection of a t~me-integrated sampler. Tile sampler t~c0~3s~sts primarily at As} ordinary pint Bilk bottle equipped with a two-hole rubber stopper ttro~h which 1/4 in. copper tubes are provided for intake of sedim=~-~aden water and escape of air. This sampler fi31$ ~e . 1 _. .- -. Numbers in parentheses refer to Publications of the Sedimentation Divi- si on, 1939~1940, p. 95.
Alibi ~ __ 94 -- . . . gradually and causes very little disturbance of flow. Because the sampler can be placed ~n position Sickly, no valve arrangement on the entrance aim exit tubes has been found necessary to prevent filling to cadence before the desired sampling point is reached. This type of sapper has several advantages, the most important of which is that it also mar be used as a flow meter after careful calibration. Other advantages are that (2) a time average instead of an insta;ntanecus sediment concentration at ~ point is obtained; (b) several sampling units may be easily minted on ~ single rod to obtain ~ vertical distri- bution of sediment; ma tc' the sample need rlof be removed droll tile sampler before being taken to the laboratory (5~. me work of the cooperative laboratory at the Cal~tora~a Institute of Technology was continued d:urin,~ the year in the fields described in pore - Gus reports. From its inception, this pro ject has been engaged in studying various phases of the problems of erosion and sedin~tation with the ot jocti~ of prodding base c intonation and principles that would be of assistance ~n the ultimate solution of p~ac~cicai problems confronting the Soil Conservation Service. In general, each individual study deals with some aspect of the mechanics of sediment movement and fluid flow aired has for its objective the determination of a relationship or law that Fill eclair the causes of some phenomenon of erosion or sedimentation and thus point the way to the application of this information to soil conservation practices. The studies have been carotid on under the follo~ring; general classifications: (1) T.fechani cs of transportation of suspended sediments by water. (2) Turbulonco as a [actor in the transportation of sediment in suspension. (3) ~o mochax~ics of t:~=sportation of bed load. (~) Hal and physical-composit~on of sod~monts in relation to the method of transportation nod dopo$~tion. (~) The phonomonon of stratified flow (density currents) in Sirs in relation to the transportation of sediment by water. (6) Protection of channels below drops. (7) Design and developraent of suspended-load samplers. Considerable progress has been made in all fields of investi~a- tions, as shown in the papers and reports of Knapp (123, Rome (17, IS, 19), Bell (2), and Otto (13, 14~.
~LICAI~ONS OF IRE S:~)IP~=Oll Drawl: ON, 1939-1940 Exhibit E _ _ 1. Barnes ~ F. F., Eracbel j C. J. ~ and L - Lotte' R. S. Erect of Accelerated Erosion on Silting in Morem Reservoir, San Diego -County, Calif. tin cooperation with the Forest Service.] tJ. S. Dept . Agr ~ Tech. But . 639 ~ 21 1?P ., illus. 1939. 2. Bell, H. S. Minored Mud Balls, Their Origin, Properties, and Role In Sedimentation. Jour. Geol. vol. 48, no. 1, 31 pp., i 11 us. 1940 . 3. Brown, O. B., and Barest P. F. Selected Annotated Bibliography on Sedimentation as Related to Soil Conservation and Flood Control. U. S. Soil. Conserv. SerY. MP-2Q, June 1939. Mimeographed ~ 4, Connaughton, M. P., aloud Rough, J. [. Advance Report or the Sedimentation Survey of Lake Bee, Monroe, North Carolina. U. S. Soil Consent. Serv. 8~3-34, 23 ppe, Talus. October 1939, 5. Dob son, O. C., and Johnson, I. W. 9. studying Sediment Loads ~n Natural Streams . Civ. Engin. vol. 10, no ~ 2, pp . 93-96, ill us . 1940. 6 . 31:akin, H. M. Silting of P`eservoirs . U. S. Dept . Ague. Tech. afoul. 524, 142 pp., illus. 1936. Premised by Carl :3. Brow, ~ 939 .] 7. Glymph, L. it., Jr. Silting of :Reservoirs. Ix~ternatla Union Geod. Ed Geophys. Round-table Discussion. Washington, Sept . 13, 1939 . (~imoographed) 8. Knapp, S. C, Stream and Valley Erosion and Deposition. Inter- nat!~ Union Geod. and Geophys . Ro,wd-table Discussion. Washington, Sept. 13, 193g. (~imeo,graphed) , Ritterrhouse, Gordon, and Dobson, G. C. Some Principles of Accelerated Stream and Valley Sedimentation. Us B. Dept. Agr. Tech. lBul. 695, 135 pp. ~ illus. 1940. 10. Johnson, J. W. I~ansportatiLon of Sediment by Streams; Bed Load. Inte~at1. Union Geod . Ad Geol~hys . :E: ound-table DO s cuss on. Washington, Sept . 13, lO39 ~ Mimeographed ~ 11. , The Transportation of Sedin~lt by Flowing Water, TI. S. Soil Conserve. Serv. ResearcI}. Sed~3ne3:~tat~0I1 Div~si on, April ~ 1940 . (Mimeographed )
1~b it -- 9 6 -- 12. Happy R. T. Density Currents. InternatI. 1; Geod. and Geophys. Rmud-table Discussion. Washington, Sept. 13, 1939. (M~ograpihed) 15. Otto, G. H. ~ ~Oaifi" Logerith~ric Probability Graph for the Interpreta*ton of Mechazaicai Analyses of Sediments. Tour. Sodiment~y Petrology, vol. 9, no. 2, pp. 62~7G, illus. lgag. 14. ~ am Rouse, Tint - . Wind-~ne, Classifier for Sand and Silt. Civ. Engin. 94~4~ 5, July 1939. I5. Pittenhause, Gordon. The Pipette Method \£oditied for AS Production. NatI. Res. Council, Ad. Gecl. and Geog. Cam. of} Sedimmiat~on Pail, inhibit G. pp. 88-102, Slept ant er lg39. 16. Ritter~ouse? Gordon. ~ Method cE Comparing Hoavy l~neral~s in Sedim - Wary Deposits. (abstract.) .Geol..~ac.: Amer. Bull Prod. Do, no. 12, (pt.2) ~ppe 19~-1931. ~c. I, 1939. 17. Rouse, Haters An analysis of Sediment l~portation in the Light of fluid Turbulence. U. S. Soil Conner. Serv. {EP-25, 25 pp., illus. July 1939. (Mimeographed ~ 18. . Laws of Transportation of Sediment by Streems Suspend . ed Cad. Internatl. Union Geod. and Geophys. Round- table Disenesion. Washington, Sept. 15, ]939. (]Eimeo- graphed) 19. . Criteria for Similarity ~n the Transportation of Sediment. . Eydraul ~ Conference Proc. ~ Union o ~ Iowa Studies in Eon Bull 20' June 1940.
