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<br />6. COLORADO URBAN HYDROGRAPH PROCEDUF\E (CUHP) (From Vi'lssman. I_e'wls. <br />Knapp) <br /> <br />The Colorado Urban Hydrograph Procedure provides 5-mlnute syntlletlc unit <br />hydrographs for use in the D'onver metropolitan area. It is based on Snyder's method and <br />is considered applicable to walersheds in the size range from 90 acres to 10 square miles. <br />with "regular" shapes (length ," 4 times width). It was developed in the early 1980s and <br />modified in 1984 to reflect refinements from early applications. In its pre-I984 form. tile <br />SynderlCUHP C, and Cp values are: <br /> <br />C- 7.81 <br />r p~_ 78 <br /> <br />(IV 1:;) <br /> <br />CO .C O. 89 c,c '" <br /> <br />(IV16) <br /> <br />Where P, is the percent imperviousness. Thes<l regression equations were developecl for <br />P, > 30%, using data for 96 storms over 19 urban watershecls. The giv<ln equations apply <br />to normal watersheds conditions and n<l<ld to be adjust<ld for Sl<lep. flat, or sewered <br />basins. If an urban ar<la is fully sewered, th<l calculated C, from Eq. (IV-15) is decreased <br />10%. If sparsely sewered, a 10% incmase is made. If th<l average slope, S of the lower <br />80% of the main water course is flat (less than 0.01 ft/ft) the C, value b<lcomes: <br /> <br />Ct <br /> <br />3.12 <br />po 71: ("0 :2 <br />a " <br /> <br />(lV.17) <br /> <br />and for steep areaS (5)0.025 It/ft): <br /> <br />Ct = <br />p~ 78 So 2 <br /> <br />3. 75 <br /> <br />(IV.le) <br /> <br />The Cp coeffici<lnt is determined from Eq. (IV-' G) and adjusted to 10% up or down for lully <br />or sparsely sewered conditions, respectively. <br /> <br />For CUHP applications equations for widths of the unit hydrograptl are: <br /> <br />V1fso <br /> <br />500 A <br />Q" <br /> <br />(IV-1!)) <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />7-44 <br /> <br />CRtVT <br />