Spikes/Excess Flow in Ras Mapper

[Yakcm]

I am trying to do an inundation for a dam breach using the mapper tool (2D analysis). The dam breach is modeled as a flow hydrograph with a max breach flow of about 7900 CFS calculated from HEC-HMS (Image 1). The model runs great with no errors. However, when I start to look at the profiles and their associated flows, something seems to be very off. The flows immediately downstream appear to be reasonable (Image 2), but as I go further downstream, I start to see inundated peak flows upwards of 2-3 times (sometimes more) than the max breach flow (Image 3 and Image 4). This doesn’t happen in real life!! I have messed with the computation times and nothing I do seems to help. Has anybody had this problem? What can I do to fix it? Is there a thread that will address this issue? I am about 40 hours into messing with it and just can not seem to make any progress. Thanks!

IMAGE 1

IMAGE 2

IMAGE 3

IMAGE 4

[cameron]

Can you post your model somewhere?

[Yakcm]

Sure, I would love to. What is the best way to do that? I have never used a forum like this.

[Yakcm]

Cameron, I have made a google drive with the model. It should have everything in the folder. I recreated the model, but am having similar problems. Here is the link.

https://drive.google.com/drive/folders/1FvVfmvHWBuOeXpGQPIgS2gSgbFFycUJ-?usp=sharing

Thank you for looking into it!

[cameron]

Your timestep is way to high. You need to follow the Courant criteria and since since this is a dam break, you probably should be using the full momentum solver as well.

[Yakcm]

Cameron, I got reasonable flows. I did more research with Courant criteria as well as using the full momentum solver. Thanks again.

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