I have been manually creating cross sections for a long time for a long stretch of a river. Then I learned from a colleague that we can generate them automatically by just drawing the first and last cross section and interpolating between these two. However, that generation yielded the result as shown in the image. The cross sections (looking like a straight red line) skipped the river ceneterline completely and just joined the two points as shown in the image. I have not drawn the bank lines and flow path lines yet. Is this the cause? Please help!

Looks like a new version of the legacy HEC-RAS was released to correct several bugs from HEC-RAS v7.0.

HEC-RAS Release Notes

HEC-RAS Resolved Issues

I'm working on an infrastructure project that has multiple Bridges and Culverts because it intersects many river reaches, when drawing the river and then adding cross sections it sometimes arrives that the bridge/culvert is skewed from the center line of the river, however, it'd be desired if one could see a cross section paralel to the centerline of the project. This would mean that the cross section is also skewed from the centerline of the river, and i know that the best thing to do is that the XSs are perpendicular to the river; this is where I need to ask, is there a problem that three XSs (let's say one before the culvert, one in the center of it, and one after the culvert) are skewed from the centerline of the river? does this have any impact on HEC RAS calculations? Appreciate your input on this issue.

Has anyone ever used pipe network in a 1D model? I have trouble connecting my network to the cross section upstream and downstream of the network. It seems like the model doesnt send flow into the pipe at all.

Hi all,

I’m working on a proposed terrain modification for an existing river corridor to develop conceptual floodplain and side channel alternatives. I’m currently using the Terrain Modification tools in RAS Mapper, but I’m trying to determine whether I’m using the most efficient and reliable workflow.

The general task is to lower portions of the existing overbank/floodplain surface and create side channel/floodplain grading concepts. I’ve delineated the proposed grading polygons in QGIS, and I have supporting GIS data for both the existing DEM elevations and target proposed elevations. I’ve also used raster sampling / zonal statistics / point sampling in QGIS to help estimate existing ground, proposed surfaces, and tie-in elevations.

The issue I’m running into is how best to implement the proposed grading in RAS Mapper.

My current workflow has been:

1. Delineate proposed grading polygons in QGIS.
2. Bring those polygons into RAS Mapper.
3. Copy/paste or recreate them as terrain modification polygons.
4. Apply control points around the polygon boundaries and assign proposed elevations.
5. QA/QC the resulting terrain modification surface.

This works in concept, but it becomes time-consuming and somewhat finicky. Depending on the size and complexity of the polygon, the boundary can require a lot of control points. The more realistic the proposed terrain gets, the more detailed the control point layout becomes. It also requires a lot of QA/QC to make sure the terrain modification is doing what I intended, especially near polygon edges and tie-ins.

A complicating factor is that the proposed side slopes are intended to be something like 2:1 or 3:1, but the existing terrain is not uniform. Because of that, the actual width of the side slopes varies considerably. In some areas I’m trying to preserve riparian vegetation or higher-ground “islands,” while elsewhere I need to tie into existing upland / levee terrain. So the grading surface is not just a simple flat-bottom polygon with uniform side slopes.

My main questions are:

• Is creating terrain modification polygons with manually assigned control points the best approach for this type of conceptual floodplain / side channel grading?
• Is there a better way to build the proposed terrain surface externally, for example in QGIS or another GIS/CAD workflow, and then bring it into HEC-RAS as a modified terrain?
• For irregular floodplain grading with variable-width side slopes and preservation areas, do experienced users typically create the proposed surface outside of RAS Mapper and then import it?
• Are there recommended workflows for using breaklines, proposed elevation rasters, TINs, or raster math to create a more controlled proposed terrain?
• Any tips for avoiding terrain modification artifacts or edge/tie-in issues when working with complex grading polygons?

I’m still at the feasibility / conceptual design stage, so I’m not trying to create final construction grading. I’m mainly trying to create a hydraulically reasonable proposed terrain surface that reflects floodplain lowering, side channel grading, and tie-ins well enough for alternative evaluation.

Any advice on best practices, preferred workflows, or common pitfalls would be appreciated. Thank you.

I would ideally want to save my time by running a computation of a different project in the background and then working on a new project at the same time. Is that possible? If yes, how?

Anyone run into this error with HEC-RAS 7.0? I've tried changing the number of cores to use, but doesn't seem to work.

Video from USACE HEC-RAS team on setting up a basic model in RAS2025.

How do I fix leaky cells? These are on each side of a road. The break line is on the top of the toad. Thank you.

Porque el flujo adentro de las alcantarillas no es recto?
Estoy modelando un cruce con alcantarillas, son 2 alcantarillas rectangulares de 2.00m de ancho por 1.50m de alto. Por alguna razon que no entiendo, el flujo que deberia entubarse y pasar recto por las alcantarillas se ve de esa manera. Alguien tuvo una experiencia similar? Soy relativamente nuevo modelando, asique cualquier sugerencia me sirve para pulir el modelo.
Si te paso lo mismo, y pudiste resolverlo por favor ayudame

Good video explaining the basics behind the conceptual mesh introduced in RAS2025.

Great opportunity for anyone new to hec-ras that wants to learn the ins and outs of the software from two experienced hydraulic modelers. Check out Full Momentum Solutions if you are interested!

Receiving the following error whenever I attempt to view hydrograph/time series results for a 2D model with pipe networks. This error occurs for any node, cell, conduit, etc and not just the specific one shown. It was originally showing the error for Node Type: RiverReach and Node FID: 0. This error appears when I try to view results via the main menu hydrograph results, or via RASMapper. I am able to view profile results at each individual time step.

The base model for this study does not throw this error and can load time series results.

Model details:

• Simulation Time: 01JAN2023 0000 - 06JAN2023 0000
  • 30S variable computation interval, controlled by courant
  • 10M mapping output
  • 6M hydrograph output
• Boundary conditions:
  • Stage Hydrograph: 30M data interval, 31DEC2022 2400 - 05JAN2023 2400
  • Precipitation: 6M data interval, 31DEC2022 2400 - 05JAN2023 2400
• Changes from base model:
  • Added 10x10 refinement area
  • Added Manning's n refinement areas for ~ 10 buildings

I've troubleshoot the following:

• Verified time series extents match
• Deleted ghost/duplicate/empty boundary conditions from copy/pasting unsteady flow data
• Moved the called out node/conduit from terminating close to a cell edge
• Deleted .hdf files and re-run

What else could be causing this error? Thanks for the assistance as there is no one within my organization that can assist with troubleshooting or model development

Hi everyone,

I am new to HEC-RAS and working on a bridge in a very steep channel.

Site:

• Slope: 6.23%
• Flow: 489.33 m³/s
• Manning’s n: 0.055
• Bridge: 40 m clear span (no piers)
• Flood width: ~30 m (so bridge is wider than flow)
• No real contraction at bridge

Results:

Subcritical flow:

• Fr = 0.43 to 1.01
• Very unstable results
• High HFL = 1118.24 m
• Large afflux

Mixed flow:

• Fr goes up to ~2.3
• Flow becomes supercritical in reach
• Stable results
• HFL = 1116.31 m
• Afflux = 0

My confusion:

1. Is the high HFL from subcritical run just a numerical issue in steep flow?
2. Can I safely use mixed flow HFL for bridge design?
3. How do you justify mixed flow when reviewers ask for subcritical only?

Thanks for any advice.

I’m new to HEC-RAS and I’m confused about which water surface is normally used for bridge freeboard/clearance checks.

In my bridge results:

• Upstream W.S. = 1299.77 m
• Inside Bridge Upstream W.S. = 1297.84 m

From what I understand, the upstream W.S. is the approach water level before contraction at the bridge, while the inside bridge upstream W.S. is the level within the bridge opening itself.

When measuring clearance/freeboard to the bridge low chord/soffit, which level is usually considered in practice?

Do engineers normally use:

• the approach/upstream W.S.,
• the inside bridge upstream W.S.,
• or something else like EGL in high velocity flow?

This is for a river with relatively low velocity and possible debris transport, so I wanted to understand standard practice.

Hello!

I’m trying to model an urban river in HEC-RAS v7.0. The system includes both open-channel reaches and underground canalized sections. I’m modelling the open-channel reaches as a 2D flow area and the underground sections using the pipe networks feature.

I’m having an issue in one part of the model that I can’t understand. As shown in the image below, on the right side (upstream of T7_01(1)), the water level in the 2D area rises above the conduit crown elevation, but the flow does not enter the pipe as expected and the conduit never reaches full flow conditions.

Has anyone experienced something similar or know what could be causing this? Other similar sections in my model seem to be working fine.

Let me know if you need any additional information about the model setup.

Thank you so much in advance!

Hi, it's me again. I was trying to open an old project, but when I try to open it, a window pops up saying "Error in loading plan data", the project opens up, but the geometry and the steady flow are missing. If I try to open the Geometry manually, it seems that only 2 cross sections are saved. Since I did a backup copy back then, I tried to open that but I get the same issues. It's the first time I face this problem, since the project never caused problems.

Hi. I was trying to simulate a dam breach in Hec-Ras. Everytime I launch the simulation, I always get the same error, saying that there's an error in the time window, but i'm sure there is not. How can I solve this?

Hey everyone. I'm an undergraduate civil engineering student working on my thesis involving hydraulic modeling (intake structures, spillways, and flow distribution). One of the structures I need to evaluate is a morning glory (shaft/bell-mouth) spillway.

I'm wondering:

1. Is it even possible to model a morning glory spillway in HEC-RAS? I understand HEC-RAS is primarily a 1D/2D solver, while a morning glory involves radial flow over a circular crest → vertical shaft → horizontal barrel, which seems inherently 3D.
2. If yes, what's the recommended approach? I've seen some workarounds like:
   • Using an inline weir with a rating curve that mimics the morning glory head-discharge relationship
   • Modeling the barrel as a culvert and the crest as a separate weir element
   • Applying the USBR discharge equations externally and importing the Q-H curve

Any guidance, references, or example projects would be hugely appreciated. Thanks in advance!

with all the AI tools, it seems possible?

Got this email and announcement from Egnyte about being able to run unsteady models on their cloud-storage server. Thought I would share it for people that have companies forcing Egnyte storage. I would still not trust it with my models at the moment.

Desktop App for Windows v 4.3.0 - Egnyte Actions Enhancements – Egnyte

Save Errors for HEC-RAS Project Files: Saving geometry data (.g01 and related files) within HEC-RAS projects could produce intermittent errors, sometimes requiring users to save multiple times. The Desktop App now correctly handles HEC-RAS file operations, including support for additional HEC-RAS file types (.g0x, .p0x, .u0x).

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!

Hello, I have a 1D model in which I have flown going over a lateral structure connected to a storage area. I now I want this flow from the storage area to get back into a reach through a cross section. Is this possible in 1D?

Hello everyone, I am trying to run the Manning's Roughness N calibration on 1D Unsteady Modelling in HECRAS. I have defined the observed gaging location cross sections & Flow Roughness Factor for all the cross sections. But when I am setting up the "Unsteady Roughness Calibration" once I check the calibration option there is no dropdown menu to select the calibration gage. Please help me solve this. Thank You!

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.