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APPENDIX A <br />HYDROLOGIC CALCUALTIONS - UNNAMED TRIBUTARY <br />Ref: SCS, 1980. Procedures for Determining Flood Flows in <br />Colorado. <br />100 Year Event <br />Drainage area: 151 acres, planimetered from USGS quad. <br />Average slope: Elevation difference from top of ridgy to <br />culvert: 6792-6450 = 342 feet <br />Channel length: 6000 feet <br />Slope = 342/6000 = 5.7% <br />Precipitation: P24hr-100yr = 4.6 inches Fig S-7 <br />CN; Soil Description Soil Group % Use CN <br />LTE Louviers Travessilla C 30 Pasture/Range 85+ <br />LT Louviers Tra,-Rock D 30 Pasture/Range 85+ <br />PP Olney Progresso B/C 30 Forest 70+ <br />TM Manzano Loam C 10 Pasture/Range 80+ <br />Weighted CN: (85x0.3+85x0.;+o0x,3+80x.10) = 80 <br />Runoff: <br />For CN = 80, P = 4.6; Q (inches) 2.55 (pg. 60) <br />Equivalent Drainage Area: 250 acres (Fig. E-1.) <br />Slope correction: for 5.7%, 250 acres, (Table E-1.) <br />slope factor = 1.14 <br />Equivalent Peak Flow: <br />CFS/inch Runoff, for 250 acres 110 cfs/in (Fig. D-2) <br />Runoff x CFS/inch x slope factor <br />2.55 x 110 x 1.14 = 320 cfs. <br />