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<br />
<br />T?.e primar>' use of recorded flo«'s ar.d pre-
<br />cl;. ;::+;ion records in the computation o, an
<br />i::::p\': ccslen °ood is the determination of a
<br />Ilcii;:rapa and of retention logs characteristics
<br />of ;hc \c;.;ershad. Dc•tai!s red; rdir.;; these anal.
<br />~-:•.: arc prcaenled in sections ~I. .i'_, and v3.
<br />V,'i:rr•• s:rcamrloir record of su:'ir.unt Icn~th
<br />t> :....:~:w!e. a fn•gnenc}' cr,r':e n;a•; be conput•
<br />rr. !;• cite proced~are outlined in section 59,
<br />-0Z. lYotcr:hcd Data.-a!I ncai!ab!c itltorma-
<br />tiu^ conccrninr r:atcrshcd characteristics
<br /><hoaid be a~semb!ed. .-~ map of the area abocc
<br />tha ('.:.^:='.:c should Ue prepared shouir.~ she
<br />drat^.~~• ~}'stcm, contour.: i` acai;aLlc, drain-
<br />,_~ i ,~;:ndarics, ; nd locations of and' preciplta-
<br />ti.a: -...;:oas and sireamt;o\c gaoir.~ stations.
<br />..,.:!;:b:e (!a:a on soil ;:pc=, coccr, ar.d land
<br />t:<a~•, , rocide caluab!c ;;u:des to judemcr,t.
<br />golf ...::, s prepv'cd b>' the Seil Conser•:ation
<br />Scrcice of the C.S. Department of A~riculUne
<br />\+~II pro•;e hclptul t:hcn :!:^ ~•:;.tershed lies
<br />........ arc;.s so m::ppcd. ; he aca:iabi2i;:: of
<br />:1:!~ ,': i, H'.Ta;l O]) IS d:SC UFcCd 1: PCCli 011 ~~.
<br />'i!•• r::;:;necr prrparin the ,`food study
<br />:~U;:. ~.: :.C;n:C• al: I.^.~;',CC::O.^. ;rl;.: O': C:' :}l l' ~`:a:C:'-
<br /><!:,',! ',n ': C'I'll t' dl'al n:g(C a!'Ca t10ti!1(la!'1CP and
<br />•i! :~~,:! cocrr in;'orni::;iott, ar.d to dclcrmntc
<br />.. :: no u(ur.iri'u;stir:: a.rc:u arc inclu(Icc •'.rh-
<br />:n .i~c dr;::n::~c hound::r:cs. Thu trip .,ituuld
<br />:~:>~, :;:r!ude chits ro nearbc \eatersheds if 1; is
<br />n::iir:;~:,:cd t!:at rccurd~ iron; nu;+rbc v:atcr-
<br />-{•~•.' : \cia I,c u;cd in the iC•Id'•'.
<br />:3 Fo:rors ro be Considered in Esrimotiny Ffood
<br />Frovis.-(;U <:(,rcvul.-Floou iorm u!as primnr-
<br />F::ce been deri\ed from ;:nd arc (lirecud
<br />'.•~l::+r~: pC'ak dischar;c computation=. Peal:
<br />I~:":',:Ire calucs os major OCOCIs ;:ru mere read-
<br />ii_r ub:::itt::UL] fetal columc c;:iues; he.^.ce, there
<br />;u'e mare data ac;rlable far peak discharte<.
<br />Fu\•:r:r.', in most i:a:anccs, the columc of t•un-
<br />(f ..<<oclatcd kith ;he peak u:scharee ::nd its
<br />;:rr•, c'.I :ribution is of city! cenccrn to the dc-
<br />•rli~r<, o:ile usually' nec(I a h~(!ro;:r::Ph, ni the
<br />ul!i..:•. ,ic;it;n hood. i~ur ;his rc::~~~n, as \ccll as
<br />iur u;hcr rrasuns t0 Lc (Iiscus,cd la[ct•, flood
<br />ivrn:li!:I; can Lc con<idcrcd only' :a a t•unlc to
<br />~mhr.:ln:u'y ;hint:u,~ ;uul for making cum-
<br />~':1:.. U.^.
<br />'Tile ,ic•C:il u-i;h v:hich hc~drol~cic cumnu[a-
<br />t,ons n_rd be mat's in pr(•parini; :. flood ~tud}•
<br />i •
<br />l.. ~_-.....T -~
<br />depend on: ill the character and anp!i,abil-
<br />it}' of the streamfo:c tiara a\aii::blc. ::..c (21
<br />the relationship of spill :•: a;: cost [o o: era:; ro;t
<br />of the project. In regions ei hi~:h I.ainfo:i po-
<br />tential, the cost o` a spillo:a., adeGu;:;e ;,; pre-
<br />veu: i;:ilure ion:cur.:cs makes ccrs:roc:io:: o; a
<br />(lane e~ceedin~l.: cOc;!)•. Fw' imnoruu',: ~ru;•
<br />ect~.:uul par;lr,;;arl v:hcre the spar.::;: ~,.1 i.
<br />a major item o; project cos: and thus :. :-avc
<br />an imJ)os~t::r.; bcanr.; on the tcav6:!it?' of a
<br />prolrc:. [hc best po~si'u;c use o: s:r~::r:,uv:
<br />Baia s?totad be r:cde. The ^::drolo~:c >.::dics
<br />refit:ued in s•.tclt uls:ances z.e e.e;ran:ri:.' com-
<br />plcs, ,.::d cors:t!:a:ion tci;h an cn~::;oar or
<br />h_: dl'O~O~IS: C>:PC':~iCnCCd in t'.:a ',: o:-k i. .ccom-
<br />mende(i. For sr,:all project>, cr for tiro,E proj-
<br />ect, it: •::hich spiil•.ca~' capac:;} is OS;a::::.',:r at
<br />r-
<br />1'elai:t'ell' loc. COP:. 1 SIL nC:!` ~: aiQ)1'OX::L..::On
<br />of ;hc in ~o:•: dc~i~:: flood disc4ar~c r.::.;: Le
<br />determined L~ procedurd; disct:s:e;i .,. this
<br />cha;acr.
<br />C]a1i.:lial ......^.1 \'r 25 Of S:I'C.^.'a~0:'. 1'C'CL:' ~.; GO
<br />IIOI )>I'O\'lOC I'C'.:a OiC C;; LT.a:_< 0: .....
<br />p:ch::'+Ic flood ui.c`,r::acs. ~.:c;..^,::'.o:•: :ors'.,
<br />p l'M'IC!C IIIC 1"C•1::((O.^:::: i) Gi:t:'CC^ -: ~`:. _. ,~..~.-
<br />c:J):..^.LOn :1 I1C : II P. C:! :.:tf! 11::0:'^la!10!: O:'. :.... d'~
<br />di=u'iSuuan. Tit., ('°:err.:i:::~::or. ~.; ,... n^:n-
<br />imt:m ta'obab!c I'OO' ~iwcld Lr ba<cc! o:::. =:ndy
<br />of <torm poter.ual, ranw` po:rnu:::, a: run-
<br />of? dlsu'iuution ::~ rc:a;cd to :he phi-:c::. ci:ar-
<br />::riurisuc: et ;hr v:;r,er>hrd.
<br />Each ~trc•am an(1 r.lch ~ :ir.~ <tauu:: ut a
<br />d:-::in;lgc area pr'c-en;- ar. .::cn:d::^1 ..+!cm
<br />Lcc;nl<u of the caryin~ ra:r.fall (lic:r. ~u;wu
<br />at:(1 du~erent rune:.` citvac:crtstics. I: :; net
<br />DOS SI b!C CU CSpI'Ci3 aII iaC :OI'i al~C'l tl l._ ;'UI W:f
<br />in unc =imply iormu;a for :::! :•:a:cry:'tr('-. Tile
<br />simplici;\' o; ;hc Cauor.a, \]etf10(! io:mula.
<br />~1=Ci.-1, t•:hirh is iamtliar to cn~in-acs cn-
<br />countc'iug problems o:` rune:' e,:in::r.c-.:- (lc-
<br />crp:icc in t:'tat :: prnpa' cralu::hor, of ::,e co-
<br />C:~•CICIII, C, tad I"Ill ll; all I1'.ii'n<:i':, !, I~ :;111'C;
<br />a detailed h>drolo;•IC stud.: for each r.plJlica-
<br />tiul:. Eu;;inc(a's con;ici•_rln~ u,c ul ,... (ur-
<br />mc+la should realize that t':c rc!iabili;••' of the
<br />resulu dr(•rea,cs ;': i;h increase in TiL'c of ,!ruin-
<br />:1a'C arCa.
<br />~Or (100(1 l!C';erm:na :10::5, data CO::. Ct'N n;r
<br />the folloc:ink :actor; for each site ne:ii ;o k,c
<br />as<cm Llcd and s;cdird: Ecc~raphlcal kcauon,
<br />
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