flow too large, x-sect too small

[plecocq]

I am having problems getting DAMBRK to run a piping failure model. I was able to run the program using an inflow hydrograph taken from a Probable Maximum Flood Study. I encountered problems when I used the results obtained from running BOSS BREACH as the input data for DAMBRK. I assume the model is not running because the flow is too high for the cross-section areas. I added flood plains to either side of the cross-sections, but the model still does not run. I was only able to get the model to run by increasing the cross-section top widths, but this does not represent the actual topography of the downstream channel.

Can you give me any tips on to how incorporate the higher inflows without changing the original topography?

[Chris Maeder]

DAMBRK will warn you that it is needing to extend the cross sectional geometry upwards to contain your routed flow (if the analysis makes it that far).

I would recommend "simplifying" the model down, so you can determine the source of the error. I sometimes will delete cross sections, one by one, off the downstream end of the model until I can get DAMBRK to run. This allows me to determine which cross section(s) are causing problems.

I would not recommend adding floodplain top width areas. In my experience, it only compounds the problem.

Sincerely,

Chris E. Maeder, M.S., P.E.
Senior Technical Engineer
chris.maeder@bossintl.com