Dam Breach HEC-RAS help required?

[rroussel]

My project is a sludge pond that has an volume of approximately 26 acre-ft. The pond has 0.0619 cfs pumped into it. I am performing a Dam Breach Analysis in HEC-RAS to model what would happen in the event of dam failure. The pond is approximately 5 feet below grade and 11 feet above grade to the top of berm. There is 2 feet of freeboard from the water surface to the top of berm. I have set the water surface in the pond at this operating water surface. The problem I have in the model is it shows water exiting the pond at the initial stage of the model (it shouldn't) and then it shows the water level below the breach elevation after 2 hours. I had calculated the parameters using the Froehlich method with a breach formation time of 0.175 hours and breach width of 18.64 feet. I also didn't use an initial flow because the pond is operating at a water surface 2 feet below the berm with the 0.0619 cfs entering the pond and leaving the pond on the opposite side of the pond where I am modeling the dam breach. Does anyone have any suggestions or tips? I expect the dam to breach causing a flood wave, which drains into a river adjacent to the site. I didn't expect the water level to drop below the bottom of the breach. Thanks.

 

[SMIAH]

The fluid properties may obey either the principles of non-Newtonian (mud/debris flows).

I'm not sure whether RAS can simulate this (?).

 

[SMIAH]

*or Newtonian (water).

 

[rroussel]

Is there a program better suited to show this or another way to model this?

 

[SMIAH]

NWS FLDWAV can do so - but if you're not familiar with it, I wouldn't recommend it.

I guess that simulating it as "clean water" can be taken as the critical case.

One thing to remember is that RAS can't perform a dam break analysis on dry bed. You should probably enter a "pilot flow" to maintain wet conditions downstream.