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<br /> <br />IV, <br /> <br />HYDROLOGIC ANALYSIS <br /> <br />IV.I\.. <br /> <br />Storm Water M~nagement Model <br /> <br />May 18, 1980 <br />New Mercer Canal Looking Northerly <br />From LaPorte Avenue, Canal <br />wasn't carrying irrigation water, <br /> <br />The hydrologic analysis for thp. West vine DraLnage Basin was <br />prepared using the Bnvironmental Protection Agency's Storm <br />Water Management Model (S.W,M,M,) as modified by the Missouri <br />River Division of the Corps of Engineers, The model is based <br />on kinematic wave theory and is directly applicable to urban <br />areas, The model takes into account various rainfall losses <br />such as evaporation, inadvertant minor depressions and <br />interception by vegetation in a parameter called depression <br />and detention losses. In addition, it also accounts for losses <br />due to infiltration through the soil surface. The M.R.D. <br />version of S,W.M,M, allows the routing of flows through <br />reservoirs and through storm sewers or open channels to <br />account for ch~nnel storage, <br /> <br />IV,B. <br /> <br />Rainfall Data <br /> <br /> <br />Rainfall data for the hydrologic analysis was taken from the <br />12) <br />[,arimer County Storm water Man;>tqement Manu"l, The 2,5,10, <br />25,50 and 100 year design storms were analyzed for both <br />",:xi"'tinq "nd futur~ d<:,v<:'lof'I""'l'.t condition,;" H>:,nc<>forth, d""lS'1' <br />storms for either existing or future development will be <br />referred to as year existing or year developed design <br />.storms, Five minute interval, two hour design storms were <br />used for the analysis, The design storms <In., illustrat.,d in <br />Table 1. <br /> <br />IV.C. <br /> <br />Subbasin Delineation <br /> <br />May 18, 1980 <br />Larimer County NO. 2 Canal Looking Southeasterly <br />From T3ft Hill Road Between W, Vine Drive and LaPorte <br />Avenue, Canal wasn't carrying irrigation water. <br /> <br />The West Vine Drainage Basin was divided into 88 SUbbasins as <br />illustrated on Figure 1, The extent of subbasin delineation <br />was based on several f3ctors. The delineation was detailed to <br />the extent that pe<J.k rates of runoff ....ere available at numerous <br />locations of interest and great flexihility wa~ 3vailable to <br />provide numerous subbasin combinations for analysis of several <br />alternatives, The S,\'J,M,M, "omputer model is a physically <br /> <br />-13- <br /> <br />-14- <br />