A few errors and workarounds I have found when generating several 2D unsteady scenarios (ie proposed with 5-foot culvert, proposed with bridge, existing conditions, duplicate effective plans/geometries) in HEC-RAS 6.6 and 6.7 (beta as of March 2025).
There is nothing more frustrating than being at the end of a project, only for your lastest change in mesh editing or fine-tuning of that mannings roughness value to throw a bug in your 2D model. Here are some best practices to avoid the pitfalls of a glitches/errors:
Rename your perimeter when saving as a new geometry.
Do this in the attribute table through RAS mapper, make it unique
You have to do this for each recurrence interval AND scenario, ie proposed conditions-100yr AND proposed conditions-50yr AND existing conditions-100yr, etc
RAS has handled 2-3 iterations fine, but will not properly work after that
Do the same with your unsteady flow file
It would be nice to reference the same 100-year hydrograph flow file for proposed and existing conditions, but I found this problematic. I have had models that dump no rain on the mesh, or misread the outlet boundary condition since it referenced other 2D perimeters.
This killed about a day of troubleshooting on a project that had a tight timeline, and a relatively complex 2D model with 16 different plans. This drove me nuts, and I couldn't find where anyone had the same issues online, so I hope this helps someone.
If your model is running faster than normal and there is 0.0000000 error in volume, thats a sign (also, no actual results might clue you in)
Update your SA/2D connections to/from
this is required everytime you do #1
Sometime, this will throw errors in the cell # your culvert barrel dumps into. An easy fix is to edit any barrel and move it slightly. This forces a "recompute" of sorts on all barrels. Keep an eye out for the blue warning messages in your computational output file.
We will keep it quick and simple for now. Check back in for more tips!
