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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 channel 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'f"I"'!'-t condition.,. H>:,nc<>forth, d""iS'!' <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 "n., 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 Taft 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 factors. The delineation was detailed to <br />the extent that peak rates of runoff "'ere available at numerous <br />locations of interest and great flexihility wa~ available to <br />provide numerous subbasin combinations for analysis of several <br />alternatives. The S.W.M.M. "amputer model is a physically <br /> <br />-13- <br /> <br />-14- <br />