Help with errors from dam breach model

[mgil2015]

Hello everyone,

I am attempting to run a dam breach model (unsteady flow) in HEC-RAS 4.1.0, but I continue to get the following errors. I have tried many things to stabilize my reach but nothing seems to work.

Is anyone able to decipher these error messages for me?

Thank you!

“Geometric Preprocessor Version 4.1.0 Jan 2010
1 Internal Boundary curve(s) have been read in and will not be recalculated

Finished Processing Geometry

Performing Unsteady Flow Simulation Version 4.1.0 Jan 2010

**** Solution Solver Failed ****

Minimum error exceeds allowable tolerance at 21SEP2008 2400

LostPond Upper 1201.299
WARNING!

***** Extrapolated above Cross Section Table at: *****

LostPond Upper R.S. 1201.299
LostPond Upper R.S. 1151.40*
LostPond Upper R.S. 1101.51
LostPond Upper R.S. 917.3005

Finished Unsteady Flow Simulation

Writing Results to DSS
Finished Writing Results to DSS

Reading Data for Post Process
Simulation went unstable at: 22Sep2008 00:00:10
Resetting post process profiles to end at: 21SEP2008 2400

Running Post Processor Version 4.1.0 Jan 2010

Finished Post Processing

Task Time
Preprocessing Geometry 0.14 sec
Unsteady Flow Computations 2.36 sec
Writing to DSS 0.70 sec
Post-Processing 0.52 sec
Complete Process 3.73 sec
Computation messages written to: x:\Clients\State\R-03887_2014_Western_District_Dam_Inspections\Lost Pond Dam\EAP_LimitsOfPotentialFlooding\HEC-RAS\FloodInundation.p02.comp_msgs.txt”

[Anonymous]

Suggest that you look at HEC-TD-39 for info. on applying HEC-RAS to dam breach modeling. From the errors that you are seeing, I suspect that the initial conditions are bad. To start the model there must be finite depth everywhere. Also, the extrapolation errors are a clue. Check that the tables of hydraulic parameters cover the expected extent of the water surface elevation at all computation points – including the reservoir (if you are using unsteady routing there). Then, address the issues of time step and other computational parameters.

[mgil2015]

Yes the TD-39 paper has been a big help, thank you for your advice! I also have found that adjusting the time step makes a big difference when it comes to stability.

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