Lack of Cross Sectional Information

Chris:

I have a proposed reservoir project which may require a dam break analysis. The reservoir will not impound any surface water courses. It is a wastewater reclamation pond and the only inflow other than what is pumped is precipitation. It is to be a rectangular reservoir, with earthen embankments at 3:1 (H:V) slopes. It will be approx. 35-40 feet in height and will store about 900 acre-feet of irrigation water.

There is a highway downstream and downslope of the proposed reservoir which is critical. There is also a river approx. 5,000 feet downstream and downslope of the reservoir. My point is that there is no channel or existing flowpath to the river or highway. It will flow downslope, but establishing cross-sections may be difficult.

Can I use Dambrk to run a breech analysis without inflow hydrographs and with very little channel or X-section data? How valid would my data be?

I appreciate your input. Thanks.
Bob Allen
rallen@sheafferinternational.com

Dear Robert Allen :

This is one of those judgemental things that you have to sort of come up with. I would assume a channel width that widens as it travels downstream. The steeper the incline, the narrower the assumed channel would be. However, I have modeled similar conditions before, and got some decent results. It turned out in my study that the assumed channel width did not have that huge of an impact in the computed water surface elevations--although that may differ in your case. However, it will give you an approximate "worst case" answer that should be able to suffice for the purpose of the study. Of course, time of dam failure is also another big unknown, and can also greatly affect your study results.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

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