r/HECRAS

Hi all. This is a bit of a weird one and we can't find much information online about it. A while back we received a RAS model from an external entity. When we went to open the results in RASMapper, they were empty. No asterisk, no error message, just completely empty. My coworker even tried re-running the model to no avail.

This occurred again today, except it was with an internal project. My coworker was reviewing a model and said he was able to see the results yesterday, but today they are empty. I confirmed on my own that the results are indeed empty. I tried removing the results file and then re-adding it into the project folder but that did not work.

Any thoughts aside from trying to re-run the model? It's not a terribly long run, about an hour, but it seems weird this is happening.

Thanks!

What is the most accurate method to trace overbank flowpaths so I can get accurate reach lengths between cross sections?

I had an existing model for hcfcd from m3models.org , when adding a new cross section by interpolation the reach length values were inaccurate.

Then I used the ras mapper tool to generate reach length , and it changed all reach length values same as Centreline value.

Hi I'm trying to run a model with a very windy river and a road that runs over it and then also next to it. how many cross sections would you draw in and how would you draw them in this case? i tried dog legging them, but the model didn't seem to do a great job interpolating the continuous raised road bed (it's not raised up very much). The red at top and bottom are the extents of the survey. sides are the floodplain overbank areas. River is flowing north if that matters.

https://preview.redd.it/fmhyyatuv32h1.png?width=1066&format=png&auto=webp&s=6646fb867c564b0c89c94851b9d9bc53d9ba01a9

I have problems with merging terrains in ras mapper versus merging rasters in GIS. They never line up and there’s a small shift compared to individual rasters before being merged. What’s the best practice?

Hi everybody,

in my company Hec-Ras 6.x is currently the standard for 2D unsteady flow computations. I personally am looking forward to switching to HR 2025 as soon as possible, but we're not yet sure weather it is already practical.

What are some of your first impressions with the program? Is it better than HR 6.x? Is it already usable für 2D computations or are there still to many bugs and issues?

Hey everybody.

I am modeling a Dam Break cascade model in HEC RAS. Is it better to model the reservoir as a storage area, or if I can keep as a 2D flow area?

For both dams, I have a DEM with great resolution (0.5m), so I thought that it wouldn't be a problem to let as 2D flow area. Also, I am not sure which one is better regarding model stability.

Both dams are flood control dams.

I've been reformatting structure data in GIS to differentiate between top/side inlets for RAS7.0. Each top or side inlet is categorized by type and data values correspond to state DOT standards, based on throat/weir lengths.

How can I import a table of values that contains standard values for each "type" of side or top inlet? I am able to import a shapefile with all nodes to populate the Nodes layer, but it does not populate the secondary attribute tables for the top and side inlet types. I have tried to re-import each separately for top/side inlet type's attribute table and it says all features are incompatible. I don't want to have to manually input this data once we have established standard values for each inlet type. Is there another format that this data should be in?

Hello everybody.

After running a model for the first time I got some results. Now changed my mesh with more breaklines and refinement regions, and also the cell size. The simulation is still running as I am writing this, but I am already asking myself:

• How can I validate the mesh that I created?
• What can I do to compare different meshes? What result should I look to?
• Does HEC RAS have some results for 2D flow simulations that can help us to see if its making sense?

I'm having an issue where my calculations get corrupted because Windows keeps switching the decimal separator from a period to a comma due to IT settings; is there a way to change HEC-RAS to a "European" format?

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Hi all,

Looking for a sanity check from folks who’ve dealt with BLE models and hydrology updates.

Here’s my situation:

• I have a 1D steady‑flow HEC‑RAS BLE model that was built ~5 years ago

• Geometry and cross‑sections are unchanged

• I recently updated the HEC‑HMS model using current land cover and imperviousness

• I now have an updated design flow at the watershed outlet from HMS

• The original BLE RAS model applied steady flow at the most upstream cross‑section (standard steady‑flow setup)

In steady 1D RAS, I can only apply flows at flow change locations, and practically speaking that means the most upstream XS to run the model.

Question:

Is it acceptable/best practice to simply replace the old steady discharge with the updated HMS discharge at the same upstream flow change location, assuming that XS represents (or reasonably approximates) the watershed outlet?

I’m not changing geometry, not converting to unsteady, and not adding lateral inflows — just updating the magnitude of the inflow. Conceptually this seems consistent (same inflow location, improved hydrology), but I want to confirm this aligns with accepted BLE / HEC‑RAS practice and wouldn’t raise red flags in review.

Would appreciate thoughts from anyone who’s done BLE maintenance, FEMA work, or agency reviews.

Thanks in advance.

Hi everyone,

Following my previous post about initialization issues, I now managed to run the simulation in HEC-RAS 6.7 Beta 5 (October 2025), but I’m facing instability during the unsteady flow computation on a river network model used for Water Surface Elevation (WSE) analysis.

Here’s the context of my study:

1D unsteady flow simulation
River network model (multiple interconnected branches)
LiDAR-derived terrain (1D cross section based geometry)
Focus on WSE behaviour across the network

The geometry preprocessing completes successfully and the simulation starts, but it becomes unstable very quickly after initialization.

⸻

Important detail:

The solver does not fail immediately, but diverges within the first hours of simulation.

⸻

Error message:

**** ERROR: Solution Solver Failed ****

Minimum error exceeds allowable tolerance
Time of failure: 01JAN2020 07:00:00

**** Warning: Extrapolated above Cross Section Table ****
Rio Apartado (RA1), Rio Leon (RL1, RL2)

Overall Volume Accounting Error: 7431 (1000 m³)
Percentage error: 282.5%

Simulation went unstable at: 01JAN2020 07:15:00

What I already checked / observed:

Geometry preprocessing runs without errors
Model starts correctly but becomes unstable very early
Mass balance error grows very quickly (~280%)
Instability appears on multiple branches of the network
Extrapolation warnings appear during the run

⸻

At this point I suspect the issue may be related to:

instability in flow routing across the network
discontinuities between cross sections or reaches
sensitivity of WSE propagation in early simulation time
vegetation (trees along riverbanks) affecting LiDAR-derived terrain and introducing local elevation errors
or boundary condition effects in a branched system

⸻

Has anyone experienced similar early divergence and solver failure in 1D unsteady network models in HEC-RAS 6.7 Beta?

Any advice on what typically causes this kind of rapid instability would be really appreciated.

Thanks in advance.

How close do you have to have your existing conditions model to a duplicate effective model? I’m expanding a bridge by 60 feet and having changes in floodway elevations by more than 0.1’.

Hi,

I’m currently learning HEC-RAS and trying to improve my practical understanding of hydraulic modelling and flood simulations. If anyone is comfortable sharing some of your old HEC-RAS projects/models (academic, practice, or any professional examples with non-sensitive data), it would really help me assess and improve my workflow and understanding.

I’m especially interested in:

- River/flood modelling projects

- 1D or 2D simulations

- Bridge/culvert modelling

- Terrain preprocessing workflows

- Manning’s n calibration examples

- Real-world project structures and organization

https://preview.redd.it/whgcum3ul30h1.png?width=1071&format=png&auto=webp&s=0e17025e2acbaa00e45ae3a29fa79352048076ee

I used to get this error sometimes when editing geometry and trying to save. But it would always go away after reopening the RAS Mapper. So, I had not given it much concern. But this time, I keep getting this error whenever I wanna draw a profile line to look at the different profiles available. The reopening thing is not working. And the issue exists in only this model and drawing the profile line is really important for me to analyze my model. Can someone please explain the reason behind this issue and tell me how can I solve it? I really dont wanna redo this model because it took so much of time for me to prepare this model.

Hi everyone, this is my first time posting on Reddit, so sorry if my message sounds a bit strange. I’m trying to run a long unsteady simulation (2020 full year) on a river network model in HEC-RAS 6.7 Beta 5, but the simulation crashes immediately before any actual computation starts. Current error message:

“+STOP! Error in the time window.
HDF_ERROR trying to close HDF output file:
HDF5-DIAG: Error detected in HDF5 (1.8.11)
H5Tclose(): not a datatype”

Here’s the context of my study :
- Unsteady flow simulation
- River network model (1D with terrain / mapper)
- Initially using daily inflow hydrographs for the whole year 2020
- Computation interval initially 15 min
- Output intervals tested at 1 day and 1 hour

I already checked/tested:
- Corrected geometry issues (I had “edge line self intersections” before, now gone)
- Rebuilt mesh / preprocessing
- Created a completely new plan
- Tested with constant inflows instead of imported hydrographs
- Tested short simulations (a few days)
- Deleted temporary HDF files
- Checked river station ordering and cross sections
- Simulation still crashes instantly with the exact same “time window” error

Important detail:
The solver never really starts. In the computation summary:
“Unsteady Flow Computations <1”

So it looks like the crash happens during initialization rather than during hydraulics.

At this point I’m wondering if:
- this is a time window alignment issue,
- a corrupted plan/project state,
- or possibly a HEC-RAS 6.7 Beta HDF bug.

Has anyone seen this exact error before or has ideas on what to check next?

Thanks!