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<br />acres shall be allowed. specific details of the required input for <br />this version are available in the CUHPE/PC version Users Manual. <br />Both the COOPD (large m;3Iinframe) and CUHPE/PC (personal computer) <br />computer programs can be obtained by contac1:ing the Urban storm <br />Drainage and Flood control District. <br /> <br />The COOPE/PC computer program was modified te, provide the <br />capability of estimating hydrographs for small drainage basins <br />(generally less than 90 acres) for which the original COOP method <br />is not applicable. Th43 resulting flood peaks in many cases are <br />generally comparable, but not identical to those es,timated .by the <br />Rational Formula as specified in the USDCM. '1'0 estimate a <br />hydro graph for small basins requires the input of the time of <br />concentration as comput'E,d by the Rational Method de,scribed in the <br />USDCM. It is often advantageous to generate a storm hydrograph to <br />facilitate the routing of flows through det,en.tion facilities or <br />channels. <br /> <br />4.4 storm Flow Analysis <br /> <br />When determining the design storm flows, the e:ng.inee,r shall follow <br />particular criteria and guidelines to assure that minimum design <br />standards and uniformity of drainage solutions are maintained <br />throughout the city. 'rhe information present'3d herein shall be <br />used by the design engineer in the development of design storm <br />runoff. <br /> <br />4.4.1 <br /> <br />On-site Flow Analysis <br /> <br />When analyzing the flood peaks and volumes, the design engineer <br />shall use the proposed fully developed land use: plan to determine <br />runoff coefficients. In addition, the engi1l1e.3r shall take into <br />consideration the changes in flow patterns (from tche undeveloped <br />site conditions) caused by the proposed street alignments. When <br />evaluating surface flow times, the proposed E;it:e grading shall be <br />used to calculate the time of concentration or the CUHP parameters. <br /> <br />4.4.2 <br /> <br />Off-site Flow Analysis <br /> <br />The analysis of off-site runoff is dependent on t.he development <br />status and whether the tributary off-site are;:l lies within a major <br />drainageway basin as defined in the City of GrE,eley Comprehensive <br />Drainage Plan. In some cases, credit may be giv,en for detention as <br />defined below. <br /> <br />4.4.3 <br /> <br />Tributary Area Within a Major DraiIlA!;reway Basin <br /> <br />Where the off-site area is undeveloped, thE' runoff shall be <br />calculated assuming a fully developed basin as d,efined by the city. <br />If this information is not available, then the runoff shall be <br /> <br />4-2 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />