Laserfiche WebLink
• CRDA N0. 2 EAST COLLECTION DITCH DESIGN <br />References: Procedures for Determining Peak Flow in Colorado, <br />SCS, March 1984 <br />Nate: Acreage includes an additional 2.5 acres during construction which rill <br />be drained to the hest Collection Ditch upon coogletion of the pile. <br />Area: 14.5 Acres = Aa <br />CN: 90 <br />Precipitation Event: 100 Year - 24 hour <br />Precipitation: 2.2 inches; Figure S-7, Peak Flows <br />Direct Runoff: 1.27 inches; Page 70, Peak Flow <br />Average Slopes: S = 0.25 z (Lc25 + Lc50 + Lc75)/DA <br />z = Elevation Difference, Ft. <br />Lc9 = Contour Lengths. Ft. <br />Da = Drainage Area, Ftz <br />S = 0.25(190)(610 + 1450 + 950)/(14.5)(43560) = 0.23 <br />:: • <br />Peak Flow Calculations <br />1 = Slope Length 1650'; Exhibit 51 <br />Ae = Equivalent Area = (1/204) 1.667 <br />_ (1650/209) 1.667 = 31.3 acres <br />qe = Unadjusted Peak Discharge = 45.0 cfs/in runoff <br />(31.3 acres. 16X slope, Type II storm, CN 90) <br />Figure S-lA Page 18, Peak Flows <br />Slope Ajustment = 1.08; Table E-1, Peak Flows <br />Qe = (45 cfs/in runoff)(1.27 in runoff) 1.08 = 61.7 <br />Qa = Actual Peak Flows = Qe (Aa/Ae) = 61.7 (14.5/31.3) = 28.6 cfs <br />(Revised 10-31-90) <br />• <br />CRDA2 - 4 <br />