Land Cover Association with 2D Results

[Anonymous]

In the “Manage Geometry Associations” dialog box, can anyone explain the meaning of the results rows? I’m working on a model where some of the plans are associated with the land cover file and some are marked “(None)” under that column. Does that mean the plan was run with geometry that didn’t have a spatially-varying roughness dataset associate with it?

[Anonymous]

Hello Grady
That probably means that in your Land Cover shapefile there are some regions with more than one polygons on top of them. Maybe one of them have a RAS identifier while the other overlaid polygons haven’t. Generally if you accidentally don’t assign a Manning value in a polygon, HEC-RAS puts a default value of 0,06.

Paul

[Anonymous]

Paul,

The model does not include any user-defined roughness polygons, so I don’t think that’s it. This particular model takes a while to run, so I haven’t been able to investigate this much. However, I’m pretty sure that, in that dialog box, the land cover cells in the results rows show which land cover file was used for that particular plan. Somehow I guess the geometry was “un-associated” with my land cover file when those particular plans were run. Thanks for the help!

Grady

[cameron]

In General, if the value is marked as None then it was not used in the simulation and the default roughness value was used. For the results rows, I don’t think the roughness has any impact on what is displayed. You can change the terrain in the results layer and this will update the floodplain based on the different terrain, but not change what was calculated (use same wse).

You can check the cell face roughness values to verify the correct values were used.

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