A Dam Break Analysis Using HEC-RAS

Abstract

Dam break failures are often caused by overtopping of the dam due to inadequate capacity during large inflows into the reservoir from heavy precipitation run-off. The mathematical hydrodynamic simulation models can be used for prediction of dam breach flood hydrograph, and routing the same through downstream valley to get the time series of discharge and water level at different locations of the valley. The HEC-RAS model set up was prepared using the available data in the present paper. The critical condition for a dam break study is when the reservoir is at full reservoir level (FRL) and design flood hydrograph is impinged. Various breach parameters were considered for sensitivity analysis. The present study for project comprises of three hydrodynamic simulations using HEC-RAS mathematical model (a) PMF with dam break with initial reservoir level at FRL, (b) PMF discharge with no dam break, (c) PMF without dam in place (virgin condition). The maximum discharge, water level, velocity, and flood travel time at different locations of the river downstream of dam due to occurrence of PMF dam break are presented in the paper.