A 650 ft. long concrete drainage pipe in old southwest Reno is laid as a straight section and eventually transitions to an earthen trapezoidal channel with rubble sides. The invert elevation of the pipe (i.e., the elevation at the bottom of the pipe) at the entrance is 4,562ft above sea level while the invert elevation at the pipe exit is at 4,553ft above sea level. The trapezoidal channel maintains the same slope as the concrete pipe and has a base width of 3.5 ft and a side slope of1.25:1 (V:H). For a particular storm event, the flow in the pipe is measured at 122cfs when the pipe is 70% full(i.e, the water depth is 70% of the pipe diameter). You may assume the Manning’s coefficient for concrete and earthen/rubble channel is 0.015 and 0.030, respectively.
A .What is the water depth (in ft) and diameter (in ft, round to the nearest 0.5’) of the concrete pipe?
b. Calculate the velocity (in ft/s) of water in the pipe under these conditions.
c. Once water reaches a steady-flow condition in the channel, calculate the water depth (in ft) and the velocity (in ft/s)