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<br />DRAINAGE CRITERIA MANUAL <br /> <br />RUNOFF <br /> <br />Qp = 156 ft3/s <br /> <br />3/4 Q = 3/4(156) = 117 ft3/s <br />p <br /> <br />. <br /> <br />Step 2. Using the procedure outlined in 2.2.3 of the "MAJOR DRAINAGE" <br />chapter calculate normal depth and velocity at 3/4 Qp' <br /> <br />(Qn)/(Stb8/3) = (117 x .04)/((.006);(5)8/3) = 0.82 <br /> <br />From Table 2-1 of "Major Drainage" @ Z = 4; <br /> <br />y/b = 0.461 <br /> <br />y = 0.461b = (0.461 x 5) = 2.31 ft <br /> <br />A = (5)(2.31) + 4(2.31)2 = 32.8ft2 <br /> <br />v = Q/A = 117/32.8 = 3.57 ft/s <br /> <br />. <br /> <br />T = (2 x 4 x 2.31) + 5 = 23.5 ft <br /> <br />F = V /VAg/T = 3.57 /1/(32.8)(32.2) / (23.7)' = 0.53 <br /> <br />Use V = 3.57 ft/s since it results in a Froude Number of less <br />than 0.8. <br /> <br />Step 3. Calculate C using Equation 4-8 and its definitions and enter <br />the resultant values in Table 4-6 for reach A-B. <br /> <br />C1 = V/(V+1.7) = 3.57/(~.57+1.7) = 0.68 <br /> <br />K = L/(3600V) = 5500/(3600 x 3.57) = 0.43 <br /> <br />B = KC1 = (.43 x .68) = .29 <br /> <br />At = 5minutes/60 = 0.083 hrs <br /> <br />. <br /> <br />5-1-84 <br />