Developing Fragility Curves for Overtopping-Caused Dam Breaching

Abstract Submission: The increased frequency of intense rainfall extends earthen embankments' susceptibility to overflow, which increases the risk of breaching. Current deterministic models for assessing dam breaching do not account for uncertainties related to applied and critical shear stresses. This research addresses this gap by introducing a fragility framework to assess breaching initiation by accounting for these uncertainties. Sediment transport principles are employed to establish a probabilistic breach initiation criterion. Hydrologic and hydraulic analyses connect the rainfall event with overflow characteristics. The relation between applied and critical shear stresses is classified into four distinct levels of magnitudes, and the necessity of a probabilistic approach at each level is discussed. Inputs of rainfall depth and embankment materials' critical shear stress are treated as random variables, and a range of possible values is generated using probability density functions. This random input is used for running Monte Carlo simulations, and the combination of a wide array of possible flood events and uncertainties in the critical shear stress is reflected in the simulation output. Fragility curves are developed to estimate the probability of breach initiation across various rainfall depths. The proposed framework offers the potential to improve dam safety practices by forecasting breach initiation and improving response strategies for dam failures.

Learning Objectives/Expected Outcome (Optional) :