In fluid mechanics, the theory of steady and uniform fluid motion does not allow such a flow in a horizontal channel. But such a flow is possible from the point of view of the theory of energy motion, which is interesting to me. The problem can be tested with a simple experiment. However, practice shows that laboratory flumes are usually made with a slope.
There are flume ith adjustable support ,and you one can adjust the support to make the floor of the flume horizontal. How ever when ater starts to flow there will slope in thewater surface, higher at upstream. You make be able to attain horizontal flow surface if you insert a submerged weir downsrteam and the regulate the volume flow
Dear Mohammed, thanks for your comments. I meant those flumes too. I know how to perform the experiment, but the main task is equipment. Do you know such laboratories?
For the case with the downstream weir you mentioned, do you have actual data on the horizontal surface of the flow, or is this your assumption? I think so as well. But I don't have measurement data. And this fact can have serious consequences.