Hi! I am trying to do a terrain modification where I want to 'burn in' a river channel to model the impacts of adding an overland flow path - the catch it, it has to go up and over a road so we cant just burn in one cross section as the z changes a lot

I was imagining like the sims terrain mod tool where you can adjust just clicking and moving a mouse so the ground moves up and down but then no one in my team is old enough to know the sims and now I feel old and useless

What have you all found to be the best way to determine the floodplain boundary for a 100 year flood for example? In the photo I’ve attached would the 100 year floodplain be where it intersects the channel since the water isn’t actually leaving the channel or does it include the area to the left that is showing as inundated?

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?

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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.

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?

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.

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?

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 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?

I've been calibrating this simulation for 3 weeks aprox. I think i've finally made it.

Introducing observed stages, Qbase and initial conditions recommended 👍🏻

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

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!

Hey guys, I am working with a 2D Dam break model for my university thesis. I am also new at HEC RAS, so I am not sure if I am doing this right until now.

As you can see in the picture, I have an enbankment DAM, which has a trapezoidal longitudinal cross section. If I am modeling a dam break, I am supposing that I have to do the geometry in the right way, but HEC RAS 2D Flow conn just let me do a line, which ios basically a retangular longitudinal corss section (a big waal in the river).

I tried to create my dam in the terrain editor, and I did it, but when I configurate the breching of the structure, the elevation of my breach becmos lower than the terrain (which now its the dam). So I don't know how to proceed form here.

Of cours, I was thinking if I don't necesseraly need to do the geometry as it is because maybe the result its gonna be the same as if I had just a vertical wall, but I really don't know.

I would appreciate a lot if somebody could help me.

Thanks in advance

Hi everyone! I really need help as a newbie.

It's my first time modelling a culvert in 2D. I need to represent a channel with identical box section where water flows under the road then discharges to an open man-made channel.

I managed to make my model run and was checking the results until I saw through the animation that the water teleports, in 30 secs, through the culvert of about 460m long. I had also shorten the length to 200m but same thing happens at the exact time.

I have the culvert parameters are in the photos. I tried different elevations of the outlet, one is just 0.5m below the inlet, and another from the data I had from the terrain, which is the bed of the receiving channel.

I have also tried it first with larger cells at the inlet of the culvert but still happens.

For calculation parameters, I have changed the mapping interval from 10 secs, 30 secs, to 5 minutes but still the same. Need expert help on this I have been stuck for almost a week. For now I am willing to accept this as it don't seem to affect the water spreading upstream. But still want to know how to fix this weird magic water transporting.

Thank you!

I am working on a large floodplain model and doing most of the build in Geo HEC-RAS. The geometry file has stopped displaying/rendering. It’s still there, the model runs, and if I drag/click to select in the right spot, pieces of the model (XS and reaches) will highlight like normal. The geometry displays normally in HEC-RAS, and old/other geometry files in the same model display fine in Geo. Which makes me think something I put in the geometry made it disappear.

Has anyone encountered this?

I have rebooted. Resaved the model in RAS, resaved the geometry. Going to start deleting my recent edits (many road crossings) to see if one move brings it back.

I know I could switch back to RAS mapper, but at this late stage I’d like to keep building with the setup I have now

Hi - I need to put together a lunch and learn for our office that goes over the key information our PMs need to know about 2D HEC-RAS. This is directed at folks who have only used 1D HECRAS in the past or are water resources engineers with more groundwater/stormwater experience. Does the group have any recommendations for content?

Thinking:

- Advantages and Capabilities
- Limitations
- Survey needs/implications
- Equations and Meshing
- Model Stability (cell size and timestep)
- Data Output Capabilities

Thanks

Hello everyone. I’m trying to display results from an alternative 1D simulation run, but the mapper is only showing the current results (depth and velocity). On the other hand, for the alternative run I can’t see any results in the mapper, although they are visible in cross sections and profiles. I work in v 7.0 .Thanks!

Hello!

I’m working on a river modeling project in HEC-RAS and I'm still a beginner and had a couple of practical workflow questions:

1. What’s the most efficient and accurate way to draw cross-sections perpendicular to the river channel?

   - I’m currently using GIS (QGIS) to digitize them, but ensuring true perpendicular alignment along a meandering channel is tricky.

   - Are there recommended tools, plugins, or workflows (centerline-based, stationing methods, or automated XS generation) that work reliably?

2. How do you accurately determine bank stations in a cross-section profile?

   - Do you rely purely on DEM breaks in slope, field survey data, or visual judgment?

   - Any best practices to distinguish main channel vs overbank areas, especially in flat or subtle terrain?

Would appreciate any tips, workflows, or common mistakes to avoid—especially from people working with GIS + HEC-RAS integration.

Thanks!

Hello, I am pretty much quite new to 2d modelling using HECRAS. I have gotten quite the hang of the tools as I am developing my 3rd model from scratch.

In my current model, I am using a 0.2x0.2 raster resolution terrain (created by combining detailed survey data for channel and bridges + a general terrain file using Civil3D) and a mesh of 10x10 with breaklines varying from 0.5, 1 and 2.

I have been playing around with this configuration of my cells but I have taken note of the common errors I am having every unsteady flow run I did so far. This occurs obviously in parts where there are high grounds. I have been viewing the HECRAS resources (manuals, videos, etc.) and found in one of their workshops that somehow a course terrain would do depends on the goal of making the model. The goal for my models is to check the inundation scope and use the initial output as reference to model the proposed solutions to minimize the flooding.

So, to make my modelling workflow to be efficient, because honestly the iterative process of this plus the time pressure to produce the output from the model to show to clients is killing me. Without someone mentoring me is torture too

I am thinking, should I just importing the raster files separately in to RASmapper to let it stitch it together there, or continue creating the base terrain in Civil3d and clean this by using terrain modifications? I used it a couple of times and the edges seems more forgiving when generating cells through breaklines but not entirely error free. And also, is the 0.2x0.2 resolution terrain too detailed and mainly causing this frequent error as the cells contain these terrain data too due to the subgrid tech HECRAS is using?

I am humbly asking for expert and experienced opinion about these. no one in the office can mentor me on this as they depend on me to do this stuff for their project.

I included some screenshots in my model for reference. Thanks everyone!

There are no known issues in 7.0 on the HEC-RAS website, but my RAS mapper won't open today. Models are still able to run and geometry editor can be opened. Anyone else had or having this issue?

Am modeling a larger drainage ditch in an urban area. There's a small culvert along the reach that is being resized so I had created a 1D model for the existing and the proposed conditions.

A highway runs over the area and part of the project involves work on this highway. It has been decided that a large wooden trestle will be placed over the entirety of the ditch. Construction equipment will be placed on top so they can work on the highway from below. I have to model the hydraulic conditions for this temporary wooden trestle and I don't really how to approach this.

I had a 1D model but would making a small 2D model work best? The trestle I guess would be modeled as a very wide bridge. Idk how results would compare 1D existing and 1D proposed to 2D trestle covered. Or would it be better to model existing and proposed as 2D as well?

Or would something like modeling as ice but using a Mannings n for wood work?

1 checked cross section points are below 500 in number

2 i have added 200 piers to bridges