Question

An existing trapezoidal aqueduct (b = 15 ft, S = 0.01%, n = 0.025) with a ¾:1 side slope was designed to flow at D/b = 0.30. The channel is sides and bottom are modified to increase side slope to 2½:1 and decrease roughness to 0.021. Calculate percent change in flow capacity assuming base width, slope and design D/b remain constant.

Fig: 1