Flow DS of lateral structure

[David S]

In my model I have a lateral structure to introduce flow into a bypass channel which re-connects to the main channel at a junction downstream. I had to estimate flows for each reach (main channel and bypass) and let the porgram optimize. When the model runs, it appears that the output comes up with optimized flows for each reach; however, the first two river sections in the bypass channel downstream of the lateral structure have flow that are exactly what I input initially as “best guess”. The remaining bypass sections have a different flow than the first two sections (whic I assume is the optimized flow). What is the reason for this and are the water surface elevations, velocity, etc correct if the flow isn’t? Thanks.

[Chris G.]

Sounds like the flow is being delivered to the bypass channel at the third cross section from the top. By default, I believe RAS does not allow you to connect to the upstream-most cross section, but you might double check this. You can always put 1 or 2 “dummy” cross sections at the top of your bypass channel to overcome this limitation.

[David S]

I figured that might be the case. Adding the “dummy” sections seems like a good option. Thanks for your response.

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