Assessing the Uncertainty of Embankment Breach Outflow due to Overtopping

This study analyzes embankment breach outflows resulting from overtopping using probabilistic modeling. The effects of uncertainties in the inflow hydrograph and embankment breach parameters on the breach outflow were evaluated using a numerical model that considers (1) breach parameters, including final bottom elevation, width, side slopes, formation time, weir coefficient, and water surface elevation triggering the breach; and (2) inflow hydrograph parameters, such as peak flow rate and time to peak, as probabilistic variables. The Monte Carlo method was employed to conduct 10,000 simulations for each scenario. Histograms and exceedance probability curves of the resulting peak outflows were generated, and probability density functions were fitted and evaluated using the Chi-square goodness of fit test. It was found that both the range and type of the final bottom elevation distribution significantly influence the breach outflow, with observed values ranging from 353 to 2170 m³/s depending on the parameter combinations. Modeling the inflow as either deterministic or probabilistic did not significantly impact the discharge; however, a normal distribution is recommended for representation. The deterministic breach model yielded a peak outflow that was approximately 40% lower than the maximum value produced by the probabilistic simulations, underscoring the importance of incorporating uncertainty into breach analyses.