[mlc3n3]

*Update*

Through lots of troubleshooting an error was found in the model.

At one of the downstream xsec the bank flow lengths were too long. Channel flow length was correct (around 185′), but the left and right bank flow lengths were wrong (around 850′).
I believe this happened when my flow lengths were off, I reassigned flow lengths in GeoHECRAS, clicked a wrong box, and this changed my overbank flow lengths.

Correcting this error corrected the model!

What I think was happening was HECRAS saw the long overbank flow lengths, interpreted a large area, and produced a slow down in the water. This therefore created a rise.

[mlc3n3]

GoSparky,

That is helpful information! It makes sense. Almost like a hydraulic jump, or a gradual hydraulic jump. My critical depth matches my WSEL right after the bridge where the rise is. I did some research about a rise downstream of a bridge and found info similar to what you provided:

https://www.fhwa.dot.gov/engineering/hydraulics/pubs/hif12018.pdf

Yes, I think its a case by case thing. For this project I’ve adjusted the bridge length, opening and low chord, but this only helps upstream while downstream doesn’t improve.

Thanks you!

[mlc3n3]

*Update*

The issue was resolved by the Civil Geo HECRAS technical support team.

For some odd reason the project files or project support files weren’t updating. The solution was to delete all output files and keep the “GeoHECRAS Project File”(s), and rerun the project. In the end this produced consistent results!

I tested this several ways: copying the file, copying scenario, and exporting. Consistent results!

[mlc3n3]

Hi Cameron,

Thanks for the reply! Sorry for my late response.

You were right! I was modeling a bridge and culvert at the same road. Using multiple openings was the key. I forgot about my post and eventually called CivilGeo and they helped with this.

Thanks again!

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