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<br />RECOM:\1E:\'OEO RUNOFF COEFFICIENTS <br />C(lO-YR.) <br /> <br />Therunuffcuefficientaccuuntsfurahstractionsforlossesbe(>l.'eenrainfalland <br />runoff which may vary with time for a given drainage area. These losses are <br />caused by intercepting vegetation, infiltration into soils. retention in surface <br />depressions, evaporation and tran~piration. In determining this coefficient, <br />different climatological and seasonai conditions. antecedent (existing) <br />moisture conditions, and the intensity and frequency characteristics of me <br />design storm should be considered. <br /> <br />TABLE IV-l <br /> <br />Description of Land Use <br /> <br />1. 13usinessAreas <br />Fully Developed <br />Partial Development (>50% Vacant Ground) <br />Business Buffer Zone <br /> <br />Table IV-l provides runoff coefficients that vary with design storm frequency. <br />The coefficients were developed using rainfall and runoff information <br />provided in the preliminary hydrology report for the Cripple Creek Flood <br />Plain Management Study prepared by SCS. These coefficients are site specific <br />to me Cripple Creek area and may not be valid for use in other areas. <br />Adjustments to tlJese recommended runoff ~"Oefficients should be made for <br />level of development, surface type, soil type and surface slope. The <br />recommended runoff coefficients presented in Table IV-l are based on <br />hydrologic soil groups C and D. Discussion with the SCS soil scientist in <br />Canon City indicated that most soils in the Cripple Creek area fit into <br />hydrologic,oil groups C and D. <br /> <br />2. Residential Areas, Mild Slopes (<8%) <br />Multi_family,Attached <br />1/4 Acre lots or less <br />1/2 Acre lots <br />1 Acre lots <br /> <br />3. lIlllsides with Moderate Slopes (8% to 13%) <br />No Development <br />Minor Development <br />1/2 Acre lots uric,s <br />1 Acre lots <br /> <br />4. Parh, Playgrounds, Cemeteries <br /> <br />5. lJndcvelopedAreas <br />Steep Hillsides (>13%) <br />Pasture, Meadow, Flo()dway <br />Exposed Rock <br /> <br />It is often desirable to develop a composite runoff coefficient based in part <br />on the proportion of different types of surfaces in the drainage area. To <br />develop a composite nlOoffeocfficient. mllltiplythe individlla I areas by their <br />indepclldentrunoffcocfficient,sum the values and divide by the total area of <br />the basin or subbasin. <br /> <br />6. Street~ <br />Paved <br />Gravel <br /> <br />7. DrivesandWalb <br /> <br />8. R()of~ <br /> <br />9. Lawns <br /> <br />IV-7 <br /> <br />[V.!! <br /> <br />C(100.YR.) <br /> <br />0.85 <br />0.40-0.45 <br />0.55 <br /> <br />0.90 <br />0.6D-0.65 <br />0.75 <br /> <br />0.65-0.70 <br />0.55.0.60 <br />0.40-0.45 <br />0.35-0.40 <br /> <br />0.85-0.90 <br />0.75-0.80 <br />0.60-0.65 <br />0.55.0.60 <br /> <br />0.25-0.30 <br />0.30-0.35 <br />0.45-0.50 <br />0.40-0.45 <br /> <br />OA5-0.50 <br />0.50-0.55 <br />0.65-0.70 <br />0.60-0.65 <br /> <br />0.30 <br /> <br />0.65 <br /> <br />0.25-0.30 <br />0.20-0.25 <br />0.90 <br /> <br />0.45-0.50 <br />0.55.0.60 <br />0.95 <br /> <br />0.90 O.9S <br />O.SO O.SS <br />0,90 0.95 <br />0.90 0.9S <br />0.30 0.45 <br />