|
<br />
<br />.'
<br />
<br />: ,~
<br />
<br />
<br />MAR-28-2000 TUE 10:43 AM
<br />
<br />Sundquist, 1951; Hall, 1971), '!'ho recossion constant,
<br />k (measured in days), is usually osthnntcd usinl' a
<br />graphical technique that inherently depends on the
<br />j,"lll'lmont of the hydrologist performing tho bo.sol1ow
<br />'scrnration. lIenee, rec:a~f1ion f:onSltnntl!l obLnhlQd fr011:1
<br />separt\to storm "vents tend to he dill'crent.
<br />This paper US08 a data set of 20 storm events to
<br />address two issues Tolated to PMF reutiL\g, '!'he lirst
<br />issue concerns the variability of the paTlllllotcrs k and
<br />CNSTL when estimated from separate storm ev"nts.
<br />111e second issue relates to the selection of tho design
<br />pnir of STRTI. and ONSTL, and to nssessing their
<br />effects on the PMF. .
<br />'1'he layout of the paper is as follows. Firsl:, hase-
<br />no", ,;Ol,nrnt;on I. I'o1'forl11",1 on Glaoh of tl", 20 total
<br />runoff hydrogrlll'hs to obt"in surface r\lnofi" hydro-
<br />lira phs, snn (nl.o known as tho direct runo(1' hydro-
<br />grnph). The variation of the recession constn\lt. and
<br />the ndllquacy of the slll'aration procedure O1"e then
<br />investigated, Thell, for each of the 20 sl.orms, the ~IUI
<br />of the HECl model is litted to tht, observed SRI:! in
<br />order tll estimate the parameters 5TH')'!. aad CNSTL,
<br />Next, design val lies llf STK'l'L and CNS'!'l. are
<br />ohtained and llseu to route th" PMF. l,'illally, the
<br />effect of v<1rinbility of S'l'RTL and CNS'!'l. estimates
<br />on both tho PM.ll' nn<l the o\l'ort.opping oC Il:ngl(1wnod
<br />dam (FigUTo 1) is evaluated.
<br />
<br />.sr."",
<br />t f.r~/"f
<br />North
<br />
<br />
<br />Englewood Local
<br />-.......
<br />~-
<br />.-
<br />
<br />it
<br />
<br />"
<br />,,/.
<br />"
<br />-"
<br />G....nvlll.
<br />
<br />Pleo.anl Hill
<br />
<br />E""lewood O<:111l
<br />
<br />D'y100
<br />.
<br />
<br />~'igunt 1. ^ 'l'opogrDphic Mop of Lho EU'ilIQwc"xl W:.Itcr..h"J..
<br />
<br />,IAWRA
<br />
<br />FAX NO,
<br />
<br />p, 02
<br />
<br />Jlo\1fmlcl
<br />
<br />HYDROLOGIC LAYOUT
<br />
<br />The ~:nglewoor.1 watel'shr.lI ((150 mi2) j,q 1,,<,"le,1 in
<br />tho southwo.t part of Ohio (1";11\11'0 1) an'\ ""1,1I1inl
<br />fo". subb".ins: COIlviJlgton, P1CManl Hill. E"l:kwl)nd
<br />Local, and Bradford, The soil COVert1~o of tl"',,, ",,1,-
<br />bnEiin,b; is very similar, arHI corn j~ tho pr~tllfl1li";'Int
<br />vegl!t.,.,tion type. '1'he topography or U,e wnll,,.,,hrd i.
<br />relntively mild. The aVeTllge annual prec.ipit"lion is
<br />nbout 30 inchcs (75 em).
<br />The watershed di~"harges at the )!~1l!11clV,.,,(1 "til'~"
<br />Dam, This limn i~ cnller! "tll'y' (or a detrmti"" ""~er'
<br />voir) hecause it llJlCrnte~ ns temporary ~t'" "':0 ror
<br />rUlloff to reducCl the probabillLy of n,""lilllr down.
<br />f;l,Cr"nm or t,hn ~h\ll\, 111 t.hn nhfllfllHU or t'nln, thn clam
<br />hn~ cssnntial1v no wntcr \Ipstn~mn or it.
<br />II. hydrolodc st.udy by tll" Ohio )kparl.ml'1l1 of Not,
<br />lira! Rc~nurces, (lDNn, indic>\tCld thntll", ),"g1<lwnod
<br />,lam will b" ovel'topp"d during tho PMF (On.!,!n t't
<br /><II" l~!JO). The overtopping of the ,hUll violnt<'" OIlNR
<br />!'cI{ulnlillns for dam 5nrcty. The dt"ign vnJIl"~ or Ibe
<br />In~s pal'nmeters llsed hy OVNR (STItTL = 1,8 inchos;
<br />CNSTL = 0,0:1 inch/hour) wero based nn stlh.iccti;'e
<br />arguments il1t"nued to maximiz,() lhe runnfr. Ou,'inus.
<br />1y, a JJlClrC nCCllrnt.('I o~ti111ntinn nr 1,hf'tJr:c' r.lIll'lulw!trij
<br />wouh.J he to use actual rai"lhll nnd runnll' clat" of the
<br />water.hed.
<br />
<br />ExmUlMENTAL Al'PIlOACn
<br />
<br />Usinl: the unit hydl'ograph (Sherman, 1932
<br />Boufauel, 1998) concept to route the SIlIT, a mas" bal
<br />auce over n watershed can be writt.en ;,.s:
<br />
<br />. IP. LI ( I = (Q - HI
<br />
<br />(1
<br />
<br />where [] denotes n matl'ix, P is the rninrflll nOHlI1l1t,:
<br />is the rllinfnllloss. U is the unit hyuro!:,l'nph, Q i- Ih
<br />total rUIlOn., llnd D is the bagenow, gqllaiinn (L) ~L~t(
<br />that thc) elrectlve rainfall IP . L] is cOf\\,Cl"l,;d b~. III
<br />unit hydrograph [U] to SRH, [Q - Bj, In most cng
<br />ncering appliclllions. the terms on the lolt hand sid
<br />of EquRlilln (1) a,.o givel\ anll used to ,.,'lilllntr' n
<br />runofT 011 tho rillht haml side. In this sccLir.n, ho....ov.
<br />the qlmnlities \" U, Q, llncl 13 nrc "'"Ull",tl ~ 110Wll (,
<br />readily available) and nr" Ugorl to ".Umat" tl
<br />parameters oClhe r!\; nfallloss I"
<br />
<br />l',.ecipit'dion Vat"
<br />
<br />A major assumption in F.qllntion (I) i, (halll
<br />rainfall is uniform ovOf the wat(ll'~h"r!, I r..",ol'!
<br />
<br />204
<br />
<br />JOUFiNAI. or- 'HE AMERICAN WATEFi r~r.:snUI:"'I". ^, l""~~
<br />
|