A circular, unfinished concrete drainpipe is laid on a slope of 0.0025 and is planned to carry from 50 to 300 ft3 /s of runoff water. Design constraints are that
(1) the water depth should be no more than three-fourths of the diameter and
(2) the flow should always be subcritical. What is the appropriate pipe diameter to satisfy these requirements? If no commercial pipe is exactly this calculated