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Subwatershed information for "H" and "I" ditches found in Volume III, Exhbit 8 <br />Ditch H -1 <br />Ditch H -1 receives flow from Drainage Area F, Pond F dewatering pump, and local run -off. <br />Ditch H -1 exists as a trapezoidal channel, so evaluation for trapezoidal channel will remain. <br />Drainage Ditch D -H1 14% Slope Reach <br />Manning's Equation <br />Flow In a Trapezoidal Channel <br />DEPTH <br />D <br />0.300 <br />WIDTH <br />W <br />2.000 <br />Slope <br />S <br />0.140 <br />Mannings "N* <br />N <br />0.040 <br />SIDE SLOPE <br />X <br />2,000 <br />AREA= (W- D) +(X *D ^2)= <br />SIDE SLOPE <br />X <br />WETTED PERIMETER= (W) +2 *[((X *D) ^2 +D ^2) ^0.5] <br />SLOPE = X:1 <br />R= AREA/WETTED PERIMETER <br />V= (1.49/N)`(R ^.667) *(S 1.5) = <br />WETTED PERIMETER= (W) +2 *[((X <br />*D) ^2 +D ^2) "0.5] <br />Q =AXV= <br />4.24 FEET <br />R= AREANVETTED PERIMETER <br />Q REQUIRED - Peak Discharge <br />0.35 <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 />FEET <br />FEET <br />EXPRESS AS DECIMAL <br />EXPRESS AS DECIMAL <br />SLOPE = X:1 <br />D50 = 0.2 feet 3 inches <br />Drainage Ditch D -H1 1% Slope Reach <br />Manning's Equation <br />Flow In a Trapezoidal Channel <br />0.78 FEET "2 <br />3.34 FEET <br />0.23 <br />5.28 FT /SEC <br />4.12 CFS <br />3.07 CFS <br />DEPTH <br />D <br />0.500 <br />FEET <br />WIDTH <br />W <br />2.000 <br />FEET <br />Slope <br />S <br />0.010 <br />EXPRESS AS DECIMAL <br />Mannings "N" <br />N <br />0.030 <br />EXPRESS AS DECIMAL <br />SIDE SLOPE <br />X <br />2.000 <br />SLOPE = X:1 <br />AREA= (W "D) +(X "D ^2)= <br />1.50 FEET ^2 <br />WETTED PERIMETER= (W) +2 *[((X <br />*D) ^2 +D ^2) "0.5] <br />4.24 FEET <br />R= AREANVETTED PERIMETER <br />0.35 <br />V= (1.49/N) *(R ^.667) *(S ^.5) = 2.49 FT /SEC <br />TR -84 Volume XI, App. B -8 12/13 <br />