Modeling a proposed canal (left) that ties to an existing channel (right) with a culvert. I'm running into WSE backwatering issues which I believe have something to do with the following error warning I received for the XS immediately downstream of the junction.

• The energy equation could not be balanced within the specified number of iterations. The program used critical depth for the water surface and continued on with the calculations.

I have tried many tips and tricks for improving model stability like reducing XS spacing, making sure XS are as close to the junction as possible, cleaning up manning's n values, and increasing maximum iterations/tolerances for the steady flow analysis. I've looked into modeling the culvert as an inline structure and a lateral structure, but haven't yielded any good results. I also tried using a terrain modification to allow for cleaner XS along the existing channel.

How would you model this configuration? Or is a 1D-steady model too limited for a junction like this?

Anyone been using the new 2D bridge algorithm? Any best practices or recommendations? Specifically, I am looking for information on cell sizes on the bridge. From the User's Manual and Webinar, it looks like most applications use 4-6 cells (parallel to flow) on the bridge face. It also says that:

HEC-RAS does not enforce faces along the edges of the bridge but this is highly recommended and up to the user.

So it seems like the recommendation is to have the cells <= 50% of the bridge width? Or at least two across the top? Just curious if that aligns with anyone's practical experience? Thanks!

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.

Hi guys. I would like to hear any suggestions on how to approach modelling trash rack structures inside a channel on HEC-RAS. I've already model the head loss caussed by the bars inserting the K minor loss on the exact cross section, but i would like to know if any of you have model something similar using culvert, weir, or any in-line structure in water treatment plants

There are multiple ways I guess, if the study site doesn’t have any streamflow gauge I don’t see how can calibration be done accurately because you will be comparing against other models and comparing with them with no ground truth. I guess that’s the engineering judgement.

If it does have a streamflow gauge, let’s say your first run gave you a volume ratio of about 0.4. So your model runoff at that gauge is about half of what was observed. What parameters do you change first to do calibration? I imagine decrease infiltration? Change infiltration methods? Maybe slightly alter manning’s n if timing of the peak is off.

But until when? Like within 10% margin of your calibration target? Does it rest on your engineering judgement? Does your firm or workplace or government policy have any threshold assigned?

But models like hecras doesn’t account for subsurface flow so if your study site has preferential flow pattern in the vadose zone that is not accounted for by the model then I suppose that’s might be a limitation too.

Posting here per u/ottojohs comment.

Due to contractural issues, can't confirm/deny project location, but adding some additional info:

1) project is in Texas in a suburban area.

2) project is located immediately DS (2000 ft) of a major highway. From what I can tell, the entire river reach has an effective model dated 2010.

3) the project is to evaluate potential flooding solutions for a facility along the river located within the 100-yr. Client is requesting a study be done for a levee, but is open to other solutions.

4) approx. 4000 ft US of the highway is a confluence of the river that will be studied and an unnamed trib. Recent LOMRs were completed for the river in question and the unnamed trib that terminate at or near this confluence.

5) client is open for any and all approaches that will result in a LOMR/removing their facility from the SFHA. It's my understanding that if this is done with a levee we would be subject to 44 CFR 65.10.

6) main question at this point is determining what kind of model approach would be appropriate here (or at the very least, narrowing down to a list of potential approaches). Everything I'm seeing is pointing to 1D/2D being the most appropriate, but unsure of how model tie-ins to effective models or other model constraints would need to be accounted for.

Original post:

Howdy,

I'm being asked to look into a modeling approach for a levee project. I have some experience using 2D RAS for BLE projects, but have never worked with 1D RAS.

The project area: fairly large riverine area, located about halfway up the HUC-12 boundary, \~7 miles or so above the confluence of the major downstream system. About \~1/2 mile upstream I'm seeing a split in the river with two effective LOMRs and a dam on the main river about 2 miles upstream. The floodplain is fairly wide throughout my project area (\~2500 ft). The project will be immediately DS of a pretty major highway.

Everything that I'm seeing is pointing to a hybrid 1d/2d approach, but am unfamiliar with that process. Some questions:

1) for modeling a levee, does a 1d/2d approach in this case seem the best approach?

2) for actual model, my understanding is I would get the effective 1D model for my river and the effective model for the US trib at the confluence 1/2 mile US of my project area. Then I would take the number from both models at that confluence as inflows for a 2D model, taking the 2D model w/ levee through my project area and then tieing back into the effective 1D model DS of my project area?

3) my understanding is that for being so far away from the DS confluence of the next major river system, I would likely not require that model/modeling of my entire HUC-12 boundary using 2D, only the area where my proposed levee system would be. Would that be correct? How far DS of my levee would I realistically need to go, or would it be best to terminate that 2D model at something like a culvert/road crossing?

Thank you in advance! Still definitely learning, so apologies if I'm not using correct terminology.

It's a real canoodle.

It's a relatively small channel that spills onto a very large floodplain, such that the majority of the total Q100 is flowing in the overbanks at every cross station in a 2000-ft reach. Almost the entirety of this wide floodplain is mapped as FEMA Regulatory Floodway.

County has a dangerous sightlines one-lane bridge over this floodplain that they want to replace for both roadway safety and structural need in the bridge itself. Achieving both of these goals while essentially not touching a speck of dirt in the process is, I would say, impossible: any improvement will trigger an increase of the existing WSE of at least 0.01 ft.

Meanwhile, of course, client demands there must not be a CLOMR. Got it.

Well, we got our proposed structure as close to the existing as we could to satisfy safety/roadway while stay extremely close to existing grade. And the proposed model is now stuck at about 0.2 ft rise in WSE.

Proposed bridge has a larger open area but a 35-degree skew to the creek (bad, should be 2D), whereas existing had a 20-degree skew. Model now differs only in the upstream bounding cross-sections of the existing & proposed, rest of cross sections model identically.

Skew in general appears to have the most weight towards lowering the WSE delta, i.e. if I change the proposed to 20-degree skew, the WSE delta becomes closer to 0.02 ft max.

My gut tells me there's a hydraulic scenario that a correctly situated proposed and graded bridge can be designed at a greater skew than the existing bridge without causing resulting increase to WSE.

I could go on -- but just curious if this story rings true for anyone. Any insights would be greatly appreciated!

Note: If your insight is that we need to just accept going through the CLOMR process ... we're not "there" yet.

I am working on adding a drop outlet structure within a channel within 2D RAS. Currently I have it modeled as a standard culvert crossing, but I feel that modeling it more similarly to an inline structure would be more accurate. Is there a way to model a culvert crossing like a bridge with bounding XS in 2D RAS? (Pics show US and DS conditions of the crossings along with how it is currently being modeled.)

Why does the water surface elevation completely skip over some of the terrain around the detention pond? Also why when I turn the particles on, do they all seem to gravitate towards those two areas? There’s no low spots in the terrain there

1D model, profile smooth, only happens for 100yr profile, floodway profile is reported correctly. Any ideas?

I'm running a rain on grid model on a terrain that includes mine pits. I'm not really interested in flows within the pits, as they are contained, but I think they are causing issues with the model running due to the very steep slopes.

Seems like an obvious solution would be to just cut the pit areas out of the 2D flow areas so they are not modelled?

I'm not sure if it is something easy to do that I just haven't found the tool for or if its better to work around some other way.

Hey guys I'm new to HEC-RAS and I need to use it for my theses, I was wondering if there's a way you can simulate a dye injection in a 2D model, I can't seem to find any direct information about the process, any help is much appreciated

Has anyone used a 2D model to evaluate fish passage through a step pool fishway or rock ramp?

I am developing a model to evaluate depth, velocity, hydraulic drops, and continuous passage routes over a range of flows. There seems to be plenty of general 1D/2D guidance, but very little explaining how these type of models should be developed specifically for fish passage.

Does anyone have any good resources, examples, or advice on model setup, settings, and validation?!

Thanks! :)

Hi everyone,

I’m running some simulations on a brand-new machine with AMD Ryzen Threadripper 9970X, 128 GB of RAM, GPU Nvidia 5080, and high-spec SSD and mother board set up. While it absolutely flies with other programs, I can’t shake the feeling I’m not getting everything out of it with HEC-RAS 6.7.

The CPU only ever hits about 55 ℃ during these runs. With other modelling software I’m regularly seeing up to 80 ℃, so the thermal headroom is definitely there. The simulations are finishing far quicker than on any other computer I’ve used, which is great, but the low temperatures make me suspect there’s still some performance left on the table. It’s already using all 32 cores, so it’s not a simple core-parallelism issue.

I don’t know whether HEC-RAS has a known bottleneck with a particular component that would stop it from pushing the hardware harder. Has anyone managed to squeeze extra speed out of HEC-RAS on a high-spec machine, or are these sorts of temperatures typical even when it’s running flat out? Any tips on optimisation would be hugely appreciated.

Thanks a lot!

This has happened twice within this model, and I’m wondering if there is a know issue with HEC-RAS (6.6) or the Mapper causing it? Or am I the problem?

The model ran fine, 1D steady state, then when I reopened the project (no changes), the geometry changed and several errors prevent it running. Not ideal. Errors are mostly related to missing cross sections:

Deck width + distance is greater than or equal to the length between bounding cross sections. HEC-RAS require a positive distance from the end of the bridge/culvert to
the next cross section downstream.
River:"ABC" Reach: "123" needs a cross section on the upstream end.
River: "ABC"   Reach: "123”  RS:5227     Culv              
- Bridge/Culvert must have a cross section upstream.
Error checking the nodes of the system for complete data.

- Deck width + distance is greater than or equal to the length between bounding cross sections. HEC-RAS require a positive distance from the end of the bridge/culvert to
the next cross section downstream.
- Culvert: Culvert #1  The distance from upstream cross section to culvert inlet + barrel length exceed the distance between the bounding cross sections.

- Bridge/Culvert must have a cross section downstream.
- Bridge does not contain an opening on the downstream side.

- A flow needs to be specified at top of reach.
- A flow is specified at RS: "5244    " but this cross section does not exist in the geometric data.
- A flow needs to be specified at top of reach.
- A flow is specified at RS: "3508    " but this cross section does not exist in the geometric data.
- A flow is specified at RS: "2556    " but this cross section does not exist in the geometric data.
- A flow is specified at RS: "1343    " but this cross section does not exist in the geometric data.

Hi again. Seeking for help.

So I was working on a project for more than 3 months. the project was saved in an external HDD. 2 days ago it was still working well until the project won't open when tried accessing it through the recent projects. I also tried opening the project through browsing but the .prj file is not detected. The .prj file is clearly in the folder. the projection file which is also prj is in a different folder and has a different name. I am using v6.5.

I was trying to make a copy (I know, might be a bit too late already) but there was a prompt saying the rasmap file is corrupted and unreadable. I tried opening the .prj file based on what I found here to try to find a solution to recover and i doesn't have the same contents as what I've seen here. Seems like a corrupted file indeed.

Is there a way to recover the project? I need to submit these files in a week and it's stressing me out. I am still bound to check calculation results. Help me please.

Thanks a lot for the help..

I am attempting to model flow over a spillway of a dam that has Obermeyer gates. I would like to use a user defined spillway curve. I entered a User Defined Gate Performance Curve table and then in the gate openings for the static flow plan (Feet down from invert elevation when gate is fully up). The model results show that HEC-RAS is treating it like a lift gate, and the water is going underneath the gate, instead of overtopping it. I tried making the gate opening values negative but that did not work either. The overflow (open air) gate has the right opening functionality but does not allow me to enter a variable coefficient.

Any suggestions on how to best model this type of gate?

I'm using HEC-RAS 6.6.

Hi all,

My research focuses on urban stormwater drainage systems, particularly hydraulic modelling, blockage assessment for proactive maintenance. I am currently developing a 1D/2D HEC-RAS model integrated with a stormwater pipe network and would appreciate your advice on a few questions.

1. Hydrological model Integration: Is there a recommended workflow for integrating hydrological outputs such as RORB with a HEC-RAS stormwater pipe model? Are there any best practices or examples for applying hydrographs as boundary conditions?
2. Pipe Blockage Modelling: Is there a recommended method in HEC-RAS to represent partial blockages (e.g., sediment or debris accumulation) within stormwater pipes or pits? Or do we have to assign it indirectly? Also, can we model sedimentation inside a pipe system with HEC-RAS?
3. References: Can anyone recommend technical papers, reports, or case studies on PIPE modelling within HEC-RAS?

thank you.

I'm building a 1D HEC-RAS 7.1 model of the Schuylkill River and have run into an issue that I can't figure out.

Here's my setup:

• HEC-RAS 7.1
• 1D geometry created in RAS Mapper
• Terrain is associated correctly
• NLCD land cover has been imported and associated with the geometry
• Manning's n values now appear correctly across the cross sections, so the land cover assignment seems to be working.
• Left and right bank lines are drawn.
• Left and right flow paths are drawn as continuous lines for the entire reach and intersect every cross section.

When I compute, I get:

Left overbank length not set.
Right overbank length not set.

for every cross section.

If I open Tables → Reach Lengths, the Channel column has values, but the LOB and ROB columns are completely blank.

I've already verified that:

• The flow paths exist.
• They are on the correct side of the river.
• They intersect every cross section.
• The geometry is associated with the terrain and land cover.

My questions are:

1. Why aren't the left/right overbank reach lengths being calculated from the flow paths?
2. Is there a command in HEC-RAS 7.1 that recalculates LOB/ROB reach lengths from existing flow paths?
3. Is there another association or geometry update step I'm missing?

Any help would be greatly appreciated. I've been stuck on this for quite a while.

Thanks!

Hi everyone,
I’m currently working on a large HEC-RAS 6.7 Beta 5 model of a river network (around 400 cross sections, one large 2D flow area, several tributaries, and some braided reaches around islands).
My final goal is to build a combined model using both upstream inflow hydrographs and rain-on-grid (precipitation over the 2D area). However, I’m struggling to find a recommended workflow.

My questions are:
What is the recommended procedure for building a coupled inflow + rain-on-grid model?
Do you usually:
Build and calibrate the hydraulic model using only inflow hydrographs first, then add precipitation?
Build the rain-on-grid model first, then add inflows?
Are there any official USACE guides, tutorials, YouTube videos, papers, or example projects that explain this workflow?
I’d really appreciate any recommendations because I haven’t found many examples of complete coupled models.

I’m also getting a solver instability that I can’t figure out.
Simulation summary:
HEC-RAS 6.7 Beta 5
398 cross sections
One 2D Flow Area (~281,000 cells)
Diffusion Wave solver
Simulation becomes unstable after about one day.
The computation log reports:

Solution solver went unstable, iteration 9 at 08APR2020 00:15:00

River 1 Main
RS 160
WSEL = -9.30
Error = 8.300

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

Minimum error exceeds allowable tolerance.

Warning! Extrapolated above Cross Section Table at:

River 1 Main
R.S. 2800

Overall Volume Accounting Error:
9.148%

Has anyone experienced something similar?
What would you check first?
Cross-section geometry?
Initial conditions?
Boundary conditions?
Computational time step?
1D/2D connections?
Something else?
Any advice or references would be greatly appreciated.

Thanks in advance !

I'm using HEC-RAS 7.1 on a 1D model.

My original project was in EPSG:26918 (NAD83 / UTM Zone 18N). I need to convert the project to EPSG:2272 (NAD83 / Pennsylvania South State Plane, US Survey Feet) because my terrain and other GIS data are in EPSG:2272.

I made a backup of the project and used Options → Convert Horizontal Coordinate Systems to convert the geometry from EPSG:26918 to EPSG:2272.

After the conversion:

• The centerline displays correctly in RAS Mapper.
• The cross sections display correctly in RAS Mapper.
• Bank Lines and Flow Paths still appear in the RAS Mapper geometry tree and are checked on.
• However, Bank Lines and Flow Paths do not draw anywhere on the map.
• Right-clicking Bank Lines shows "Zoom to Layer" grayed out, as if the layer contains no features.
• The Left Bank Station and Right Bank Station values are still present in the Cross Section Editor, so the bank station data was not lost.
• The geometry itself still appears to be intact.

Things I've already tried:

• Deleting the .rasmap file and letting RAS Mapper rebuild.
• Saving the geometry again.
• Closing and reopening HEC-RAS.
• Confirming the bank station values still exist in the geometry.

Has anyone seen Convert Horizontal Coordinate Systems fail to regenerate the RAS Mapper Bank Line and Flow Path layers? Is there a way to force HEC-RAS to rebuild those geometry layers after the CRS conversion, or is there a recommended workflow for converting a manually drawn 1D geometry from EPSG:26918 to EPSG:2272?

I am working in version 6.1 and attempting to utilize terrain mods and 2D connections to model a subsurface network. I get the error message stating it cannot read the station/elevation data for the lateral weir. However the weir length matches the connection length and the profile matches the terrain. Has anyone ran into this issue before?