Hello there,

Open-channel flows are those that are not entirely included within rigid boundaries; a part of the flow is in contract with nothing at all, just empty space.

Steady flow in a channel can be either Uniform or Non-uniform (varied).When the average velocities in successive cross sections of a channel are the same, the flow is uniform. This occurs only when the cross section is constant. Non-uniform flow results from gradual or sudden changes in the cross sectional area.

Characteristics of uniform flow in open channel are as follows:

• Open channel flow is characterized by a flow not completely enclosed by solid boundaries
• Free surface is subject to atmospheric pressure
• Flow is not caused by external head but by the gravity component along the slope of the channel

I hope it helps.