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HEC-RAS overbank Mannning's n

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Hello, I am working with an existing HEC-RAS model. I have noticed that when I lower the manning's n in the overbank area adjacent to the banks, the water surface actually rises. I have not done any storage routing, so the flows are the same. Please let me know why it is doing that.



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  • 4 weeks later...

Hi Ashish,

That is very interesting that your water surface rises when lowering the Manning's n value. Maybe something else in your model is changing, causing your water surface to rise. I'd compare everything in your models before and after changing the Manning's value. Has anybody else seen this or have any input on this topic?


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