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<br />Ii'",
<br />
<br />2130 A
<br />On
<br />
<br />(IV-20)
<br />
<br />where A and Op have units of square miles and cubic feet per second. For alotting W,e'
<br />the smaller of 35% or O.6Tp is placed left of tile peak. for W'5' 45% IS placed to lhe left.
<br />or 0.424Tp if O.6Tp waS used for W,o' Tp is the time from beginning of rUllolf of the unit
<br />rainfall to the peak time.
<br />
<br />Several investigato", have suggested that Snyder's Ct and slope S are correlated. The
<br />original CUHP procedure was alterecl to recognize this relation, makin!J the adjustments
<br />in C, unnecessary. :=or tile modified version. Eqs. (IV-H) and (IV-18) are byoassed, and
<br />the time to peak ratller than lag time is used in Snyder's E:q. (IV-3), where:
<br />
<br />t p
<br />
<br />I L. L ""1 J. '8
<br />c..'
<br />. .S,
<br />
<br />(IV-21)
<br />
<br />'00
<br />,
<br />
<br />'"
<br />
<br />" "
<br />
<br />"
<br />
<br />'00
<br />
<br />J
<br />
<br />------------nr---------------
<br />
<br />"r=';::;'::l:~: Tf'-=~~
<br />" "-4.' . .' --'7'"1 --I
<br />~ '-:-.~_F.~=.M -~-"-,,, .:2," : !,
<br />~~ '.I!~='r"'"' .," ----.-.~=-.::r~-j
<br />'.----' 1. ' : I ' I
<br />I 'f I +=~--=i=:::~=ri=
<br />tt=-tt'--I::=F[]l=:;:~::jl
<br />. ~.:j:;. '. . - --~-+'. --.".--\-+-
<br />-,-fT -+---:---'~it-
<br />o "~;I::~ ,.. L ~~1i2-.-t~~~~
<br />o 2Q ~,() eo fa 100
<br />r.."ell irrr,."io~.,',
<br />
<br />0.18
<br />
<br />0.12
<br />
<br /> fQU'lton.Olc",w: B..icoq"~,.,,.,.
<br /> C,"JP'1-bl,.' C( \0"
<br /> .. .= 'p"CL vi;)
<br /> , .. -oO>,,~~ '0 .~
<br /> , 0.000011 -01>0"1'. .,." '.
<br />\ 3Iu<.o-4 .801.tO"'.,," 'p - ,'.... to ....~ l~rJ
<br /> I r' ,-.--
<br /> __~___~ I.,,)
<br /> i (..' ~~,.nct t.
<br /> i "'~"o>d 1...,1
<br /> \ I -~. '.'-"~"""
<br /> : I 1f1lftl
<br /> 1'-.. - 1 I
<br /> -.
<br /> : ,''' ' !
<br /> . ~.----+- ,
<br /> 1---
<br />EQ.l ..,i~ti"3~-
<br />
<br />0.16
<br />
<br />0.14
<br />
<br />0.10
<br />
<br />''''
<br />
<br />Por<;on\;mpe.....;o'".f.
<br />
<br />Figure 7-6
<br />
<br />The revised time co"fficient Ct is obtained from Figure '1 and the peak coefficient is found
<br />from:
<br />
<br />Cp ,PCr A.'J 5
<br />
<br />(IV-22)
<br />
<br />where: S ~ weighted average slope 01 basin along the stream to
<br />the upstrea.m basin boundary (ft/ft)
<br />P = coefficien;, depending on imperviousness, from Fig 7-5
<br />A = drainage area (sq miles)
<br />
<br />Colorado Flood
<br />Hydrology Manual
<br />
<br />7-45
<br />
<br />aw=r
<br />
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