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. . .
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,
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~itit I:
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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.
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~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.
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~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.
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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.
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Alibi ~
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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~.
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~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 )
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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.
Representative terms from entire chapter:
bed load
