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<br />Rex Burns, PeE, and Bob Smith, PeE, <br />Final Report - Hydrologic Analysis of the Cooper Slough Witbill Larimer COUllty, Colorado <br />Page 5 <br /> <br />Note that the discharges at the confluence with Boxelder Creek are lower than the discharges at <br />State Highway 14. This situation results from th,~ 1-25 overflow contributions from Boxelder <br />Creek. Figure 4 shows the lOG-year Hydrograph for the Cooper Slough basin with and without <br />Boxelder overflows. From this figure it can b,~ seen that the Cooper Slough basin area peaks at <br />roughly one hour, whereas the overflows peak at over six hours and contributes roughly 8 limes <br />more flow to Cooper Slough than the entire Cooper Slough bas,in, The det.1iled output files for <br />these storm events are included in Appendix D. <br /> <br />CONCLUSION <br /> <br />The existing conditions peak discharge at State Highway 14 in the original Simons & Li 1987 <br />S\VIvfM model are approximately 20% of the updated peak flows (based on the 100-yc:ar <br />discharge of 460 cfs at State Highway 14 in lhe origjnal S 1Nl\1M model). This indicates that the <br />overflow discharges from Boxelder Creek have a significant :impact on the Cooper Slough <br />\vatershed. For this reason a U.S,G.S. regional analysis, or other hydrologic check, was not <br />performed for the Cooper Slough watershed, <br /> <br />This updated hydrological analysis is now consist,mt with the Boxe.lder Creek UvTh'1P study. <br /> <br /> <br />Sincerely, <br /> <br />LO'VE & ASSOCLUES. INC, <br /> <br />("-"') f,1 \1) <br />~~- ttb-tl- 23&( <br /> <br />Da'od J, Love:, P.E. <br /> <br /> <br />DJL:sml <br />enclosures <br /> <br />cc: Dr. John Lion, P.E., P.L.S. - FEMA, Region VI[[ <br />Terri Fead, P.E. - City of Fort Collins <br />