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~'• <br />Ditch DesiQr- (A-H Exhibit 9B1 <br />Q = (1.49/Nj AR zis S ii2; Manning's Equation <br />N = 0.040 <br />R = (bd + zd2) / (b + 2d z2 + 1 <br />A=bd+ zd2 <br />s = 0.25 max., 0.05 min. <br />@d.25 = I1" Q = 34.7 CFS <br />@d.05 = 16" Q 31.1 CFS <br />@d.05 = 17" Q = 34.9 CFS <br />b = 2' for 1h:1V side slopes z = 1 <br />`~'-~ <br />Ditch required for 0.25 slope = 11" + 4" Freeboard = 15" <br />V.25 = 34.7/2.7 = 12.8 fpm <br />D50 = ((12.8) 0.25 °'~~/7.58)2 x 12 = 21.4" Rin-Rap <br />Ditch required for 0.05 slope = 17" + 4" Freeboard = 21" <br />V.05 34.9/4.8 = 7.3 Fpm <br />D50 = ((7.3) 0.05 °•~~/7.58)2 x 12 = 4.0" Rim-Rao <br />Culvert Sizes <br />Flow Required: SE Collection Ditch 34.1 CFS <br />NW Collection Ditch 23.3 CFS <br />Culvert Capacity: 30" CMP with square edges and 18" of <br />cover = 36 CFS <br />24" cup with square edges and 18' of <br />cover = 24 CFS <br />(Handbook of Steel Drainage and Highway <br />Construction Products, 1971, Figure 4-IS <br />Inlet Control nomograph for corrugated <br />steel pipe culverts.) <br />• CRDA'i - 13 Rev. 2/4/94 <br />