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I I I I I I I I I I I I I I I I I I I Figures 6 through 9 show runoff hydrographs for each recurrence interval for selected design points under future basin development Results of Hvdroloaic Analvsis TABLE 5 Figures 10 and 11 show discharge versus stream stationing for the 2-,5-, 10-,50- and 100-year floods for the main channel of Upper Lena Gulch, Apex Gulch, and Pleasant View Tributary, These plots represent peak flows for existing channel conditions under future basin development Location Lena Gulch at Hogback Lena Gulch at 6th Avenue Lena Gulch at 1-70 Inflow to Maple Grove Res, 500-YEAR PEAK DISCHARGES (cfs) 100-vear 1,770 2,270 3,810 3,980 500-vear 3,900 4,500 7,700 7,800 The peak discharges computed for future basin conditions are used in subsequent hydraulic analyses to determine limits of flooding and the flood profile along the drainageway, In addition to the analyses performed during this study to estimate peak discharges and discharge hydrographs for the 10-, 50-, and 100-year frequencies, analyses were performed to estimate the 500-year frequency peak discharge, The 500-year frequency peak discharge was estimated by linear extrapolation of log-log plots of discharge versus exceedance probability for the 2-, 5-, 10-,50-, and 100-year peak flows under future basin conditions at selected design points, The estimated peak inflow to Maple Grove Reservoir for the 500-year frequency event is 7,800 cfs, Table 5 shows the 500-year frequency peak flows at selected design points, 9 ~