Depth Grids HEC-GeoRAS

[Anonymous]

I was provided a HEC-RAS prj and when I ran it with HEC-GeoRAS for depth grids it looked like this (as it should):

http://i57.tinypic.com/14o0g43.png

I made some modifications to cross sections to implement a floodplain bench scenario, ran a steady flow analysis and imported the results into HEC-GeoRAS again. This time the depth grid looked like this:

http://i60.tinypic.com/2zr4aj6.png

What might be happening between the original model and the changes I made to mess this up?

Edit: Now that I’m thinking about it, would this have anything to do with the fact that I “excavated” certain areas and therefore changed the topography. My changes now no longer match the DEM and so it cannot produce an accurate floodplain delineation? If this is the case, is there anything I can do to remedy this?

[cameron]

If you changed the cross-section data by excavating it, you will need to modify the terrain used in Geo-RAS to match or else the floodplain may not look correct when mapping.

[Anonymous]

That does make sense, thank you. Is there a way to modify a DEM to fit my new cross sections?

[cameron]

In version 5.0 you can create terrain from your cross-sections and then merge them with your DEM. Otherwise you will have to modify it the DEM in GIS or another program.

[Author]

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