A rectangular channel 40 ft wide carries 900 cfs of water. The slope of the channel is XXXXXXXXXXAt section 1 the depth is 4.50 ft, and at section 2, 300 ft downstream, the depth is 5.00 ft. What is...

A rectangular channel 40 ft wide carries 900 cfs of water. The slope of the channel is 0.00283. At section 1 the depth is 4.50 ft, and at section 2, 300 ft downstream, the depth is 5.00 ft. What is the average value of roughness factor n? Derive the expression that gives the slope of the liquid surface in wide rectangular channels for gradually varied flow.