Consider uniform flow of water in a wide rectangular channel with a per-unit-width flow rate of 1.5 m³/s·m and a Manning coefficient of 0.03. The slope of the channel is 0.0005. 

(a) Calculate the normal and critical depths of the flow and determine if the uniform flow is subcritical or supercritical. 

(b) Next, a dam is installed (at x = 0) in order to impound a reservoir of water upstream. This raises the water surface profile upstream, creating a “backwater” curve (Fig. P13–86). The new water depth just upstream of the dam is 2.5 m. Determine how far upstream of the dam the “reservoir” extends. You may consider the reservoir boundary to be the point at which the water depth is within 5% of the original uniform water depth.

FIGURE P13–86

Transcribed Image Text:

Yn Ya Before After x=0