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<br />For land uses simulating flow in large gullies, diversions, small upland gullies, <br />an additional equation was used to calculate flow velocities based on Manning's <br />equation as follows: <br />Land s <br />Equation <br />Large gullies, diversions, and low flow streams V = 3(S)'° <br />Where: V =velocity (fps) <br />S =slope (qo) <br /> <br />Curve Number, CN <br />The runoff curve number (CN) is a factor relating the amount of rainfall to the <br />amount of runoff for a given area. It is dependent upon the infiltration <br />characteristics of soil types and the type and amount of vegetation. <br />Curve numbers were obtained from Procedures for Determining Peak Flows in <br />Colorado and Technical Release No. 55, (USDA-SCS, 1980). Based on soil <br />type and vegetation cover, curve numbers were calculated independently for <br />each area on a pre and postmine basis. <br />Premine and reclaimed land encompasses the following soil types (Ref: Soils <br />Map, Rockcastle Permit 1981): <br />Soil Name Hvdroloaic Soil Gr <br />Coutis Fine Sandy Loam B <br />Winevada - Splitro Complex C-D <br />Winevada Fine Sandy Loam C <br />Skylick Loam B <br />Hydrologic Soil Groups were obtained from USDA-SCS TR-55, June 1986, <br />Appendix A. <br />4 <br />