[alister.hood]

If you’re still looking for an answer: try checking/repairing the geometry validity.
e.g. if you have QGIS, try the “fix geometries” or v.clean processing algorithm.
Also, don’t try to import a layer with “rings” (holes in polygons), as it confuses HEC-RAS.

[alister.hood]

For the record, something else I’ve found is that I need to manually “compute property tables” after adding a terrain modification. I’m guessing this is only if I haven’t also modified the geometry.

• This reply was modified 2 years, 6 months ago by alister.hood.

[alister.hood]

Sorry, I was thinking I would get notified of a reply.
Yes, I had a land classification associated.
I have subsequently been able to run a model with this option, so I’m not sure what was previously causing my problem. I do wonder if I needed to manually run “compute property tables”.

• This reply was modified 2 years, 6 months ago by alister.hood.

[alister.hood]

I presume the cross-sections are of the flood wall.
Assuming you are building a 2D model, there are three options:
– use a 2D connection
– use a terrain modification
– modify your terrain before bringing it into HEC-RAS
I would use a terrain modification but probably also put a 2D connection along the crest.

Are you still looking for this guidance?
Is the problem that you have very many points and you need help dealing with them efficiently?

[alister.hood]

The site does have it, assuming you are looking for a Windows version. Just click on “archived versions” at https://www.hec.usace.army.mil/software/hec-ras/download.aspx

[alister.hood]

Does anybody have any tips for getting this option to actually work?
I’ve tried to use it on a couple of models and it causes this error:

Writing Geometry…
Computing 2D Flow Area ‘Perimeter 1’ tables: Property tables do not exist.
Error completing geometry for computations:
Index was outside the bounds of the array.
Geometry Writer Failed
Error Processing Geometry

• This reply was modified 2 years, 7 months ago by alister.hood.

[alister.hood]

Would using 2D be an option?

[alister.hood]

Is just importing the TIF not sufficient for what you’re doing?

[alister.hood]

> > The elevation is taken from the cell faces at the location, not necessarily the lowest point in the terrain.
>
> So when you add a terrain modification at the end of a culvert you need to make sure it isn’t fully contained within a cell, but intersects a cell boundary.
> I think I’ve picked up on this before, and then forgotten, causing myself problems…

Strange, I thought I’d replied again to this.

I’m sure this is incorrect, or at least the way I read it – I have verified that you can use a terrain modification located entirely within the cell to lower the terrain to the level you want to make a culvert.

I think in the past when I had problems setting culvert levels that I actually concluded they were related to this: https://therassolution.kleinschmidtgroup.com/the-ras-solution-forum/topic/why-ras-mapper-modifies-the-terrain/#post-15461

• This reply was modified 2 years, 8 months ago by alister.hood.

[alister.hood]

Yes, it seems to treat each cell value as the value at a point, and create a TRN joining up all those points, rather than treating the raster as 1mx1m flat surfaces separated by vertical walls.

Does that help at all?

I think it is debatable whether this way of considering the terrain is more correct, but it certainly allows for much nicer results – try resampling your raster to a finer grid (say to 0.1m x 0.1m), without interpolation, run a 2D model based on that, and you will see much uglier results. The main downside is that I think sometimes it causes difficulties with inputting levels of things that need to be above the level of the terrain (culverts and weirs).

[alister.hood]

Investigating my colleague’s CUP - Alias not found error we found that running systeminfo in a command prompt also fails – something is clearly corrupted in Windows on his machine, but like I said we don’t know if that is what causes HEC-RAS to fail or if it is just interfering with debugging.

To clarify, the model he is dealing with was also originally created in 5.07, but it was previously upgraded to either 6.0 or 6.1, and we can run it in 6.1 on other machines, so we believe the system is broken and there is no problem with the HEC-RAS model. I’ll get him to try to run a different model at some stage just to be sure.

[alister.hood]

My colleague’s problem may not be the same as yours. He gets one other error before the forrtl line. CPU - Alias not found

[alister.hood]

systemInfo.txt is an empty file on my colleague’s machine, but doesn’t exist on mine. We don’t know whether it is just supposed to be part of some debugging process, or what.

[alister.hood]

Maybe it is a coincidence, but I have a colleague who encountered this problem a couple of days ago. We haven’t resolved it yet. His model runs fine on my computer, so we’re wondering if it is caused by a windows update or something like that, which hasn’t been applied on my machine yet.
Can you run other 2D models?
Have you tried sending the model to someone else to run on a different machine?

[alister.hood]

> The elevation is taken from the cell faces at the location, not necessarily the lowest point in the terrain.

So when you add a terrain modification at the end of a culvert you need to make sure it isn’t fully contained within a cell, but intersects a cell boundary.
I think I’ve picked up on this before, and then forgotten, causing myself problems…

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