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<br />Flood Insurance Study Repolt Data <br />Flood Insurance Study - Cooper Slough, Larimer County, Colorado <br />Page 6 <br /> <br />TABLE 2 <br />1.25 OVERTOPPING DISCHARGES AT Sn,TE IHWY 14 <br /> <br />STORM TOTAL FLOW FLOW TO FLOW TO <br />RECURRENCE FROM BOXELDER COOPER SLOUGH MEDIAN <br />INTERVAL (efs) !pfs) Jefs) <br />10-year 275 ~!9 246 <br />50-year 530 173 357 <br />100-year 726 301 425 <br />500-year 1136 590 546 <br /> <br />To update the 1987 SLA SWMM model to include the dischar\1e contributions from <br />the Boxelder Creek basin, inflow hydrographs were created. Discharge contributions <br />from the Boxelder Creek basin were added to the Cooper Slough basin at three <br />locations along 1-25: at Vi 1e Street (includes the peak discharges for the Larimer-Weld <br />canal as well the Vine ~;treet discharge); at the cas Railroad (includes the peak <br />discharge for the overtopping of 1-25 south of Vine Street as well as at tl1e cas <br />Railroad); and at State Highway 14. The inflow hydrographs maintained similar <br />shapes as the Boxelder Creek basin hydrograph, but the peak discl1arge for each <br />hydrograph was set from the values listed in Tables 1 and 2. In addition, because <br />the Boxelder Creek basin hydrograph was computed for a 1-hr rainfall event, tl1e 1987 <br />SLA model was converted from a 3.hour rainfall event to a 1-hour rainfall event. <br />Table 3 lists the combimd peak inflow discharges from the Boxelder Creek basin <br />input into the updated Cooper Slough Basin SWMM model at the various locations <br />and for the various storrr recurrence intervals. <br />