CIV E 530 - OPEN-CHANNEL HYDRAULICS FALL 2011 LAB No. 5:  UNIFORM FLOW Prove that the Darcy-Weisbach friction factor is related to Manning's n by the following relation: fD = 8gn2 / (k2 R1/3) in which fD = Darcy-Weisbach friction factor, g = gravitational acceleration, R = hydraulic radius, and k = constant specific for the system of units, equal to 1 in SI units and 1.486 in U.S. Customary Units. Express the relation in SI and U.S. Customary units. A trapezoidal concrete-lined channel is being designed on steep terrain with Q = 10 m3/s, b = 1.5 m, z = 1, and n = 0.013. What should be the design bottom slope to keep the Froude number below 2? What should be the bottom slope to keep the Froude number below 1.5? The prevailing terrain slope is S = 0.0077. Would you recommend choosing a design slope of S = 0.0077? If so, why? Or, why not?