ABSTRACT:

Overtopping failures of earthen dams are a growing concern under intensifying extreme rainfall. This study introduces a probabilistic fragility framework that combines hydrologic modeling, hydraulic analysis, and soil erodibility to assess erosion risk under uncertain load and resistance. Fragility curves derived from Monte Carlo simulations quantify erosion initiation and severity as functions of rainfall depth and excess shear stress. Application to multiple dams affected during the 2015 South Carolina floods reproduces observed outcomes ranging from complete breach to no damage. The framework also captures cascading effects, where failure of an upstream structure increases downstream loading and erosion potential. Compared with deterministic approaches, the method better represents outcome variability and provides a more reliable basis for dam safety assessment and flood risk mitigation.