Assessing the Uncertainty of Embankment Breach Outflow due to Overtopping

Abstract Embankment breach outflows resulting from overtopping were analyzed 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 considering (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 the peak flow rate and time to peak, as probabilistic parameters. The Monte Carlo method was used for the probabilistic analyses. The histograms and exceedance probability curves of the resulting peak flows were obtained, and probability density functions were fitted. A Chi-square goodness of fit test was performed to examine the fitted distributions. It was found that the upper and lower bounds, as well as the type of the final bottom elevation distribution of the breach play an important role in the breach outflow. Treating the inflow as deterministic or probabilistic did not significantly affect the discharge; however, it is suggested that it can be modeled using a normal distribution. The deterministic breach model underestimated the outflow compared to the maximum peak discharges of the probabilistic models.