[Vince Moody]

Even better, I saved the changes I made to the geometry in 5.0, and when I opened the project in 4.1 it didn’t produce the same display error. You could modify your geometry in 5.0 and run in 4.1 as needed. Bizarre.

[Vince Moody]

I was able to reproduce your error in 4.1.0, but I didn’t dig into why it’s giving the error. On the bright side, I didn’t receive the same error in 5.0 beta. This suggests to me that this is a bug that was resolved after the release of 4.1. Can you use 5.0 for your project? If not, I’ll play around with your dataset a little more.

[Vince Moody]

Interesting. How would you feel about posting your model?

[Vince Moody]

Never seen this issue before. What version of RAS are you using?

Also, I would check the start and end stations of the blocked obstructions. Make sure that one doesn’t start within the footprint of another. This is an issue for ineffective areas and the program has an option to automatically fix those, but I don’t think the same option exists for obstructions.

[Vince Moody]

I think you posted this same issue about two hours ago…

First of all, your figures confuse me as there are cross sections within your 2D area. I assume you are modeling things in 2D? I strongly suggest you remove the cross sections if they’re not being used in the simulation, and they might be the entire source of your output visualization problem. Try removing the sections and re-running. Let me know what your output looks like then.

[Vince Moody]

Is the geometry of your system such that lateral inflows specified in the flow editor are insufficient?

[Vince Moody]

With 40 years of data you should be able to estimate the 100 year flow with a reasonable degree of certainty. If you don’t have enough observed data for calibration, you do the best you can and clearly and emphatically state the analysis limitations; maybe present reasonable bounds of your results. You don’t need a rainfall-runoff model, but it certainly seems like it might help you if you have sufficient data. The new version of HEC-HMS has some very powerful uncertainty analysis features you may find helpful (User’s Manual Chapter 16).

An important thing to think about is what the “100 year event” means for your analysis. Is this the regulated discharge from the system, or the “natural” discharge of the system were the dams not in place? One of those will require a lot more work than the other.

[Vince Moody]

The negative sign denotes direction of flow.

[Vince Moody]

I’ve been there, and it was a pain to fat-finger all that old HEC-2 data into the program. I had a copy of a copy of the original data and it was far from clear what was a 4 and what was a 9 sometimes. All that aside, there are some differences between HEC-2 and HEC-RAS that might be affecting your results, especially around bridges. The good folks at HEC were well aware of this when they wrote the program, so they provided ample documentation for the end user in the User’s Manual and Hydraulic Reference Manual. Check out the discussion beginning on page 3-19 of the User’s Manual, and Appendix C of the Hydraulic Reference Manual. I would make sure to do a detailed QC of the data you hand-typed into RAS, as it’s a likely source of potential differences between the two programs. Once you’re confident in the fidelity of your data, the User’s Manual has a few additional things you should keep in mind when trying to reproduce results. Good luck!

[Vince Moody]

If you post your model somewhere I’d be happy to have a look at it, but it won’t be until next week when I’m back in the office

[Vince Moody]

The channel modification tool is probably the way to go unless you want to modify your underlying terrain. The channel modification tool isn’t limited to just the channel, despite the name; you can modify just the overbanks or both if that’s what you’re looking for. It is highly customizable and you should check it out.

[Vince Moody]

What benefits would there be of using a “dummy” reach? Sounds like extra work if you have the data you need to use lateral inflows.

[Vince Moody]

Look into hydrologic routing for the portion of the reach that goes unstable. User’s Manual page 6-156.

[Vince Moody]

There’s an even easier way than exporting a depth GRID and processing in GIS: In Mapper, in the results of your simulation right click on one of the layers (e.g. Velocity) and select “Edit Map Parameters”. This brings up a dialog that lets you customize the displayed results for that layer and one of the options is Inundation Boundary. Select this option and the appropriate profile and then “Save Map”. You may need to recompute this new map result, so go to the Tools menu in Mapper, then Manage Map Results. Select your newly created inundation Boundary layer and click Compute/Update stored maps.

This creates an inundation area shapefile in the plan name in your model directory. Alternatively, you can right click that layer and export to a new shapefile to the directory of your choosing. Sounds like a lot of steps, but should take all of 30 seconds.

[Vince Moody]

Karl,

Did you follow the cross-section attributing procedure outlined in the HEC-GeoRAS User’s Manual? My guess is that you added some cross sections or moved cross sections after generating river stations/reach lengths. Try re-attributing cross sections properties in GIS and export again to HEC-RAS.

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