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<br />APPENDIX A
<br />HYDROLOGIC COMPUTATION EXAMPLE
<br />
<br />]-A)
<br />
<br />SAMPLE INPUT (SUB-BASIN
<br />,2 %
<br />A "" .358 m~ , 1a 30 ~
<br />
<br />S = 0.0123 ft/tt
<br />o
<br />
<br />1.
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<br />II. EQUATIONS
<br />1. Ct Ct
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<br />
<br />I
<br />
<br />I
<br />
<br /> p
<br /> P
<br />3. C
<br /> P
<br /> C
<br /> P
<br /> C
<br /> P
<br /> C
<br /> P
<br />4, t
<br /> P
<br /> t
<br /> P
<br /> t
<br /> P
<br />
<br />I
<br />
<br />I
<br />
<br />I
<br />
<br />I
<br />
<br />I
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<br />5,
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<br />I
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<br />I
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<br />L= 1.25mi,
<br />
<br />0.644 mi
<br />
<br />L
<br />ca
<br />
<br />(L,L ) 0,]8
<br />ca
<br />
<br />0.18
<br />
<br />S 0.24
<br />o
<br />Ct rime to peak coefficient (used with CUHPB computer program)
<br />
<br />Ge'= rime to peak coefficient (from Figure A-I)
<br />= Q. 10 for sample input
<br />
<br />C
<br />t
<br />
<br />(0, ]0)( 1.25 x 0.644)0,]8
<br />0.0]23(0.24)
<br />
<br />0,276
<br />
<br />0.16
<br />
<br />Ct
<br />
<br />0.14
<br />
<br />following values dependent upon basin
<br />
<br />I (%)
<br />a
<br />
<br />A'
<br />
<br />C"
<br />
<br />-
<br />U
<br />]
<br />I-
<br />Z
<br />~ 0.12
<br />u
<br />u...
<br />u...
<br />ll..I
<br />o
<br />U
<br />
<br />B'
<br />
<br />o to 40
<br />40 to ]00
<br />(0.002450)(30)2 +
<br />4.005
<br />
<br />+0.002450
<br />-0,00]642
<br />
<br />-0,0]20
<br />+0.332
<br />
<br />+2.16
<br />-5.05
<br />
<br />(-0.0]20)(30) + 2.]6
<br />
<br />P.C '.AD.IS
<br />t
<br />Peak Coefficient
<br />
<br />(4,005)(0, ]0)(0,358)0,]5
<br />
<br />0,10
<br />
<br />0,343
<br />
<br />Ct' [L.Lca ]
<br />-vs:
<br />Unit hydrograph time to peak (hours)
<br />O,]0[(]'25)(O'644) ] 0.48
<br />-VO,O]23
<br />
<br />0.259 hours ]5.5 minutes
<br />
<br />0.48
<br />
<br />0,08
<br />
<br />640 C
<br />qp = ----1'.
<br />t
<br />P
<br />Unit hydrograph peak (cfs/mi2)
<br />
<br />0,06
<br />o
<br />
<br />qp
<br />
<br />qp
<br />
<br />(640)(0.343)
<br />0.259
<br />
<br />q = 848 cfs/mi 2
<br />p
<br />
<br />-24-
<br />
<br />FIGURE A-1
<br />
<br />TIME TO PEAK COEFFICIENT
<br />
<br />, .
<br />~---_.-
<br />
<br />,
<br />; , ,
<br />---~-_.'i--~!----l--.
<br />, I
<br />! I
<br />
<br />i ! ;! I ,-
<br />__L__'_-L_i---i-~T-r~f---
<br />
<br />-l_~~!____Ll__
<br />, '
<br />! .
<br />
<br />_+_------L.....-"'.;_,__
<br />i : !
<br />Ii!
<br />
<br />2, A'1 2 B'1 C'
<br />p = + +
<br /> a a
<br /> P Peaking parameter
<br /> A' , B' C' = Coefficients with the
<br /> imperviousness (I )
<br /> a
<br />
<br />
<br />~i~_'_
<br />i
<br />!
<br />
<br />. , ,
<br />. - , ,
<br />- -----~--,-'-.-r---l----
<br />
<br />BASIC EQUATIONS
<br />
<br />'[L'LCOJO,48
<br />Ip =CI ,r=--
<br />r So
<br />640 Cp
<br />qp = 1
<br />P 0,/8
<br />C =C' [L'LcoJ
<br />1 1 SO,24
<br />o
<br />
<br />-~-'-~--'--
<br />!
<br />
<br />! ,
<br />'-----r-----~--.
<br />,
<br />
<br />-..---!----.!
<br />
<br />- r----'-.--
<br />i
<br />
<br />__i__
<br />
<br />-i
<br />
<br />"
<br />,
<br />
<br />, , '
<br />----:--,---,l--,.,,~
<br />, ,
<br />, .
<br />, ,
<br />
<br />20
<br />
<br />40 60
<br />PERCENT IMPERVIOUS - IQ.
<br />
<br />80
<br />
<br />100
<br />
<br />NOTE: C( is from "UDFCD Design Storm
<br />Procedure Hydrology Research
<br />Program", 8-7-81 update by UDFCD.
<br />
<br />-25-
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