HEC-RAS Question
HEC-RAS Question
(OP)
I'm doing a waterway analysis using HEC-RAS.
An increase of the channel crosssections in a certain reach of the stream leads to lower velocities but an increase of the water surface elevations. I can't really explain why the water surface is higher. Can anybody help?
Thanks.
An increase of the channel crosssections in a certain reach of the stream leads to lower velocities but an increase of the water surface elevations. I can't really explain why the water surface is higher. Can anybody help?
Thanks.





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Good Luck
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As a test, I used an old natural waterway (brook) HEC-RAS model and at two locations in separate runs I increased the cross section. The same thing happened; lower velocity, higher depth, associated of course with higher energy grade elev. and slope, larger flow area and smaller Froude #. My problem is that I still can't picture the situation. I apologize for my ignorance.
Again, my flow is subcritical, the slope doesn't really change and roughness is the same.
Thanks.
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Using Manning for a uniform (say trapezoidal or rectangular channel) for the same discharge increasing the channel width leads to smaller velocity (larger area) and water depth, isn't it? Where is my confusion Francesca?
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