Dam- Breach Hydrograph Modelling: An Innovative Semi- Analytical Approach

The delineation of the areas exposed to flood hazard caused by a dam existence upstream and its possible failure needs a thorough analysis of the hypothetical dam break incident. The study presented in this paper focusses on the simulation of the dam breach formation and the calculation of the resulting outflow hydrograph using a semi- analytical approach. More specifically the method presented addresses the dam break incident of an embankment dam caused by overtopping. The analysis is based on the assumptions of constant vertical erosion rate for the formation of the breach and the parabolic shape of the breach. Two solutions are presented dependent on whether the capacity of the reservoir is considered prismatic or it is a power function of the water depth in the reservoir. Finally the proposed method is illustrated through the analysis of a hypothetical dam break incident.