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• K =soil erodibility factor 0.37 <br />LS =combined length slope factor 400' - 2% 0.31 <br />Use Ditch Dt Length R Slope <br />C =cropping management factor 1.00 <br />P =erosion control practice factor 1.00 <br />A =sediment, tons/acre/year 3.44 <br />Three Year Sediment Volume -Acre-Feet 0.03 <br />6.76 ACRES - 115 #/CF <br />Total Required Sediment Pond Capacity -Acre-Feet 0.50 <br />Peak Flow Calculations <br />The fotlowing peak flow calculations were compiled with SEDCAD. <br />Details of the run-off calculations are shown on the following pages. <br />25-YR <br />24 HR <br />Event <br />Pond D Drainage 7.5 <br />Flow calculations for the site ditches and culverts are <br />presented in following sections of this exhibit. <br />Exh 8-18 <br />09/06 <br />Spillway Pond D <br />Pond D Emergency Spillway <br />Manning's Equation <br />Flow In a Trapezoidal Channel <br />DEPTH D 0.5 FEET <br />WIDTH W 10 FEET <br />Slope S 0.02 EXPRESS AS DECIMAL <br />Mannings "N" N 0.03 EXPRESS AS DECIMAL <br />SIDE SLOPE X 2 SLOPE = X:1 <br />AREA=(W'D)+(X'DZ)= 5.50 FeetZ <br />WETTED PERIMETER=(W)+2`[((X 'D)z+Dz)in] 12.24 Feet <br />R=AREANIIETTED PERIMETER 0.45 <br />V=(1.49/N)'(R~)'(S~~)= <br />Q=AXV= <br />Q REQUIRED -Peak Discharge <br />TR-44 <br />h1PORovE~ <br />3/ZO/a7 <br />4.12 FUSec <br />22.7 CFS <br />7.5 CFS <br />