Geometry and Flow Area Errors

[Austin Gaydos]

I am working on a very basic model of a small river reach. I do not have a ton of experience with the program, but I have been following the same methods I have used in HEC-RAS before. However, I keep arriving at an error when I attempt to run the unsteady simulation. I am greeted with the following error each time…

“flowarea: Cannot recompute 2D property tables because: Land Cover file(s) are missing.
Existing tables DO NOT match this geometry because: Associated terrain has been changed. Geometry Writer Failed. Error Processing Geometry”

It seems as though my issue originates with my land cover, but I am clueless as to what the issue is. I have a single land cover layer and a singular geometry file. The one geometry file I have has the land cover layer and terrain layer associated to it, so I do not understand the root of the error.

[Eric R]

This error, it seems to me, may be associated with different coverages between the land cover and the polygonal mesh. Make sure the land cover is not smaller than the 2D polygonal one (sometimes, a small area causes this error). I’m not sure, but check this initially.

Also, check the “Manage geometry associations” tab in ras-mapper.

[Austin Gaydos]

Hi Eric,

Thank you for the response. My land cover layer definitely covers more area than my 2D flow area mesh. In RAS mapper the mesh completely lays within the land cover layer than I am using.

My associations are also correct. I have my geometry file associated to the single and cover and single terrain files that I am also working with. I am really not sure where to go from here, so I may opt to just restart.

[Eric R]

Perhaps an error occurred while importing the land cover. The program simply doesn’t seem to have found the file.
Alternatively, you can try to import it again in a newer version of Hec-Ras.
Another aspect to note: the sub-areas of your land cover cannot have the same names (at least in my experience, this usually returns an error). But I don’t know if it applies to your case.

• This reply was modified 1 year ago by Eric R.

[Austin Gaydos]

I just attempted to reimport the land cover and nothing seems to have changed. One thing that is confusing me is that the error states that it cannot recompute the 2D property tables, however I am able to manually compute the 2D Flow Area Hydraulic Tables in RAS mapper with no issues. I am using version 6.4.1.

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