1. What is the difference between flow depth d and hydraulic depth D?

    The flow depth d is the distance from the water surface to the channel bottom. It has particular application to trapezoidal or rectangular channels, where it is a constant. The hydraulic depth D is the ratio of flow area A to top width T. In a rectangular hydraulically wide channel, d and D are approximately the same.


  1. Derive the expression for the angle θ in a circular channel (culvert) as a function of flow depth y and diameter D, where D = 2r (Fig. 1-14).

    Definition sketch for a circular channel

    Fig. 1-14  Definition sketch for a circular channel.
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