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• Ditch H-1 <br />Ditch H-1 receives flow from Drainage Area H, Drainage Area F and local run-off. <br />Because of the large flow, design as a trapezoidal channel. <br />Drainage Ditch D-H1 14% Slope Reach <br />Mannings Equation <br />Flow In a Trapezoidal Channel <br />DEPTH D 0.950 FEET <br />WIDTH W 2.000 FEET <br />Slope S 0.140 EXPRESS AS DECIMAL <br />Mannings "N" N 0.040 EXPRESS AS DECIMAL <br />SIDE SLOPE X 2.000 SLOPE = X:1 <br />AREA=(W*D)+(X'D^2p <br />WETTED PERIMETER=(W)+2*[((X*Dy`2+D^2)^0.5] <br />R=AREANVETTED PERIMETER <br />V=(1.49/N)'(R^.667)*(S^.5p <br />Q=AXV= <br />Q REQUIRED -Peak Discharge <br />. Riprap Sizing -Drainage Ditch D-H1 14% Slope Reach <br />D50 =Size of Riprap <br />D50 = ((V X S^.17)!7.58))^2 <br />D50 = Diameter in feet <br />V =Velocity <br />S =Slope <br />3.71 FEET^2 <br />6.25 FEET <br />0.59 <br />9.84 FT/SEC <br />36.45 CFS <br />35.81 CFS <br />D50 = 0.9 feet 10 inches <br /> Drainage Ditch D-H1 1%Slope Reach <br /> Mannings Equation <br /> Flow In a Trapezoidal Channel <br />DEPTH D 1.600 FEET <br />WIDTH W 2.000 FEET <br />Slope S 0.010 EXPRESS AS DECIMAL <br />Mannings "N" N 0.030 EXPRESS AS DECIMAL <br />SIDE SLOPE X 2.000 SLOPE = X:1 <br />AREA=(W*D)+(X`D^2)= 8.32 FEET^2 <br />WETTED PERIMETER=(W)+2'[((X*Dy` 2+D^2)^0.5] 9.16 FEET <br />R=AREA/WETTED PERIMETER 0.91 <br />V=(1.49/N)`(R^.667)`(S^.5)= 4.66 FT/SEC <br />Q=AXV= 38.77 CFS <br />Q REQUIRED -Peak Discharge 35.81 CFS <br />PR-07 Exh-8 - 168 - 2/03 <br />