2D Levee Breach Issues

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2D Levee Breach Issues

Lori
Hi,

I'm running multiple levee breach scenarios in SI units. My model runs fine and has reasonable hydrographs for the lateral weir structure that is breached; however, I realized that for using SI units for my breach, the weir coeff should be lower than the default 2.6. Once I decrease the coefficient, I get strange results.  The hydrograph decreases (as would be expected) however the depth grids and inundation areas are larger in the 2D area connected to the levee than the run using the 2.6 coeff. Sometimes the lateral weir hydrograph will even no negative and never have a positive "flow out" value.

Has anyone else run into a similar situation and found a fix? Thanks
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Re: 2D Levee Breach Issues

Will
Hi,

I got that negative volume issue on my levee breach project many times. I found it is related with the TW EL versus DS WS El. Luckily I managed to tune up the model to have reasonable results by changing either the breach location or breach timing.

Hope that helps.

Will
Leo
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Re: 2D Levee Breach Issues

Leo
In reply to this post by Lori
Hi, I got the same issue of having negative Weir Flow and Breach Flow values during a breach simulation. I found out that the problem was at the SA/2D Flow Area Conn.  The Connection should always be from the storage area to the 2D Flow Area. After I flip flop these two, I had to rearrange the Centerline GIS Coordinates of the connection since  the XS of a structure in HEC-RAS must be placed from left to right looking downstream.

Hope this helps!