Influence of dam breach parameter statistical definition on resulting rupture maximum discharge

Abstract

However rare, dam breach occurrences are recently reported and associated with significant damage to life and property. The rupture of the structural dam wall generates severe flow rates that exceed spillway capacity consequently generating unprecedented flooding scenarios. The present research aims to assess the influence of the dam breach statistical configuration on the most relevant parameters to predict the rupture maximum discharge (RMD). McBreach© software was used to provide the necessary inputs for the operation of the HEC-RAS dam breach module. McBreach© automates the process of batch mode simulations providing a Monte Carlo approach to characterize the breach parameters stochastically. Thus, a sensitivity analysis was performed to identify the most influential breach parameters, followed by an uncertainty assessment regarding their statistical definition of the resultant RMD. Analysis showed that the overtopping failure mode discharges are most sensitive to the breach formation time (tf) parameter, followed by the final height breach (Inv) and the final width of the breach (B), which combined are responsible for 85% of the rupture’s maximum discharge. Further results indicated highly variable RMD magnitudes (up to 300%) depending on the breach parameter’s statistical definition (i.e., probability density function and associated statistical parameters). The latter significantly impacts the estimated flood risk associated with the breach, the flood zone delimitation, preparation of emergency action plans (EAP) and scaling of future dam projects. Consequently, there is a plausible need for additional investigations to reduce this uncertainty and, therefore, the risk associated with it.