We are working with an unsteady HEC-RAS model created by someone else for a small, flat, highly urbanized watershed.
Channel by-pass flow comes out of the main channel, flows through several blocks of neighborhood in an ill-defined path, and then re-enters the main channel some distance downstream.
The original modeler used a lateral weir to depict the long stretch through which flow leaves the channel. The lateral weir crosses several roadways (which have bridges or culverts).
The model does not appear to be correctly handling the flows coming in and out of the channel, all of the time.
Can you use lateral weirs in HEC-RAS across roadway cross-sections? The HEC-RAS manual does not seem to address this issue.
If not, what is a solution other than removing the lateral weirs in the model and using a different modeling technique to represent the bypass flow?
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Karen Kabbes P.E., D.WRE, ENV SP, F.ASCE
President
Kabbes Engineering, Inc.
Barrington IL
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