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I I I III - 2 4 Table 111-1 HYDROGRAPH INPUT SUMMARY DEVELOPED CONDITION Area Length To Sub- (mi 2) Slope Length Centroid Ct C Ia Procedure Basin (ft/ft) (mi) (mi) p Used A 1. 02 .020 2.56 1.52 .48 .64 36. CUHP Bl .55 .028 1.25 .76 .37 .62 45. CURP B2 .69 .029 1. 78 .83 .39 .63 43. CURP Cl .46 .021 1.44 .57 .37 .56 47. CUHP C2 .53 .027 1. 80 .83 .42 .66 40. CUHP Dl .81 .044 2.27 1.10 .29 .56 54. CUHP D2 1. 89 .062 2.54 1.52 .33 .59 43. CURP El .56 .034 1. 52 .95 .32 .58 52. CURP E2 .22 .036 1. 33 .61 .40 .64 40. CURP F 5.14 .098 3.96 1. 78 .58 .89 14. SYNHYD AlA .18 .024 .80 .40 .46 .64 35. CURP used. A constant rate of 0.5 inch per hour was used for the la, 50 and 100 year floods. For the 2 and 5 year floods, rates of 1.0 inch per hour for the first hour and 0.5 inch per hour thereafter were used. For the sub-basin west II of the Hogback Ridge, infiltration rates were based on analysis of permeability rates for the soils published by the U. S. Soil Conservation Service. The con- I I I stant basin weighted infiltration rates used were 2.4 inches per hour for the 50 and 100 year floods and 2.5 inches per hour for the 2, 5 and 10 year floods. The effect of most existing starage reservoirs within the basin was neglected. Two existing detention basins were included because they were designed specifi- cally to reduce the rate of runoff fram their tributary areas in accordance with Jefferson County regulations. For sub-basin BlA, the amount of detention pro- II vided effectively eliminated runoff from that tributary area. In basin AlA, the detention volume provided was sufficient to considerably reduce the peak I II I outflow, and the flood hydrographs were routed through the detention pond using a reservoir routing program. On site detention for future development was not included in this study. Flood hydrographs for each sub-basin were lagged, to reflect the travel time between design points, and added. The peak discharge for each design point and recurrence interval is summarized in Table 11I-5; flood volumes are summarized I in Table 111-6. Flood hydrographs for the 2, 10 and 100 year future basin develop- ment condition are plotted for seven of the design points in Figures 111-1 I II II I II II I through 111-7. Discharge-frequency prafiles are shown in Figures 111-8 through 111-12. A copy of all of the hydrologic backup calculations is on file with the UDFCD. ~ Leonard Rice Consulting Water Engineers, Inc.