Dear Dr. Chauhan :

DAMBRK begines the dam failure once the water surface elevation is above the trigger elevation defined by "Water Surface Elevation at Time of Breach". The piping failure elevation is defined by "Piping Failure Centerline Elevation" (DAMBRK variable CDO).

The values you enter for the dam failure breach bottom width and breach side slope are the final values that you want DAMBRK to end up with.

Piping failure is assumed to start as a rectangular orifice. It gradually enlarges and ceases to be orifice flow and becomes broad-crested weir flow when the reservoir elevation lowers sufficiently and/or the pipe enlarges sufficiently that the reservoir elevation is less than [3*(piping centerline elevation) - 2*(current breach bottom elevation)]. This is explained in more detail in Chapter 6 of the BOSS DAMBRK User Manual.

Sincerely,

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