Embankment Dam Breach Parameters and Their Uncertainties

Potential flood hazards that would be created by breached embankment dams need to be evaluated to select spillway design floods and to prepare emergency action plans. The breaches are often modeled simply, usually in the shape of a trapezoid that is defined by its final height, base width or average width, and side slopes, along with the time needed for the opening to form completely. Data collected from 74 embankment dam failures were used to develop mathematical expressions for the expected values of the final width and side slope of a trapezoidal breach along with its formation time. Information is provided that allows variances of the predicted quantities to be calculated as well. The findings of the statistical analysis were then applied in a Monte Carlo simulation to estimate the degree of uncertainty of predicted peak flows and water levels downstream from breached embankment dams.