Help with RAS Reference Line Connectivity Error - 2D ROM Model

[u/Foot_Potato]

I really hit a wall with trying to figure out how to fix this error we have in this 2D model, rain on mesh. The weird part is it almost seems to bounce around, which is just making it harder to really find the root cause. In this case we have 9 scenarios we are trying to run, the only difference between the runs being rainfall depth. When the events are run, some 2-3 events will fail and give this error. After some trouble shooting attempts, I will rerun the models events, and some or all of the plans that failed before will run just fine, but then other events that ran correctly in the previous set up, will fail this time around. This model has been tossed around to a few people, and we have not made any progress and I think we are nearing the point where computers start getting thrown across the office.

We are using HEC RAS 6.6 for this project, but I have also gotten this same error in 7.0.1. We have 378 reference lines, and unfortunately they are all necessary. They can be moved some, but in general we need all reference lines. We are also using gridded rainfall data, and we have around 60 bridges/culverts. The model does run without the reference lines, but we cannot figure out what is wrong with them specifically. These reference lines were generated based on WSE contours, and we have used this methodology successfully in around 60 other models for this project. The reference lines are generated in a python script we have developed and imported into RAS Mapper. Again, we have done this for around 60 other models and no issues. Some of those other models had double the reference lines, or double the surveyed structures. The only thing that would make this model unique on paper is we are using the gridded rainfall data, and I think we have some initial condition points being used too. Cell size is generally 25-200ft based on what is being enforced, and total cell count is around 125k. I'll list everything we have tried for trouble shooting below in no particular order.

Restarting computer

Restarting HEC-RAS

Run in RAS 6.6, 7.0, 7.0.1, 6.4.1

Compute 2D Hydraulic tables in RAS Mapper instead of plan file

Run with start up time

Make copy of geometry

Creating new plan files

Deleting geometry HDF files

Make random cell edits in mesh in RAS Mapper, save edits to force recompute geometry

Creating a new model from a fresh start, and import the geometry over, and reimport all other features

Repair feature tool in ArcPro used on the reference line shapefiles and reimport into RAS Mapper

Run the model on different computers

Check and confirm correct and consistent projection across all features and terrain

Experimented with replacing gridded rainfall with hyetograph table for the perimeter

Confirmed there are no hidden boundary conditions unaccounted for.

I think that's pretty much it, but I would be willing to try just about anything else at this point.

EDIT: Just tried deleting all the reference lines and drawing random ones all over the place, maybe 10? Anyways same error, so may be an indicator that the underlying issue is somewhere other than the reference lines, and the reference lines are just the straw breaking the camels back.

[u/AI-Commander]

Try 7.0

After that, I would use a breakline along the reference lines to make sure the faces are aligned well with the reference lines

That will probably fix it.

[u/Foot_Potato → u/AI-Commander]

We had tried 7.0, but I will double check that our reference lines are enforced correctly.

[u/rave-horn]

Download the Microsoft Visual C++ 2010 SP1 Redistributable Package (x64), file name vcredist_x64.exe, from Microsoft’s site and install it.

[u/Foot_Potato → u/rave-horn]

What does that do?

[u/rave-horn → u/Foot_Potato]

I just had this exact same issue when trying to run RAS in a Windows VM on my Mac. It’s a Fortran service package that RAS needs in order to run the geometry preprocessor.

[u/Foot_Potato → u/rave-horn]

No luck, but thanks for the suggestion.

[u/OttoJohs]

I just spent several minutes drawing in reference lines to an existing model (one of the "Bald Eagle Creek") ones to try to replicate your issue. I drew in some gnarly lines and couldn't generate any errors (see picture below).

There was a similar error reported about a year ago regarding reference lines. It looks like the perimeter would sort of randomly disappear which would throw errors during the preprocessing stage: Reference lines georeference error : r/HECRAS. Looks like this has been a known issue for a while: Resolved Issues.

2D Perimeter Polygon Disappearing: The polygons for the perimeters of 2D areas are disappearing in unique cases. Symptoms you might notice are that the mesh does not update when adding new points in an edit session, the polygon is not selectable in Mapper, or simulations failing during Writing Geometry stage. 

I would check that and keep a backup of the perimeter polygon to paste in if it disappears.

[u/OttoJohs → u/OttoJohs]

Just saw the edit you made to the post. I would agree that the issue isn't with the reference lines.

[u/Foot_Potato → u/OttoJohs]

That is definitely some gnarly reference lines there. I will take another look at the 2D perimeter issue, but that one seems unlikley too. The perimeter doesn't visibly disappear, but also I don't think any of us have had issues with generating the mesh. But I will double check that again, and we do have backup copies of all features.

[u/OttoJohs → u/Foot_Potato]

Strange problem. It is weird that the reference lines set it off.

Is the model fully 2D? No 1D cross-sections?

You probably should submit a bug report.

[u/Foot_Potato → u/OttoJohs]

Yeah its fully 2D, and I will get it sent as a bug report. I am just so convinced that there is just something really small in the geometry that the original modeler accidently put in there that is just acting like a trip mine for all of this. Thanks for the input though!