Comparison between TELEMAC-2D/SISYPHE and a Slumping Failure Model to Simulate Breaching of Earthen Embankments

Earthen dams are utilized worldwide for water storage and flood mitigation. Inadequate design and poor maintenance of such structures can result in breaching failures, which may have devastating impacts on both humans and property. Since widely used free-surface flow models typically focus on the flow field by considering rigid boundaries and due to a lack of breaching models that fully characterize the breach evolution and failure process, a numerical model was developed in-house at the University of South Carolina, called the slumping model. This model captures the spatial and temporal evolution of breaching. It solves the shallow-water and sediment mass conservation equations while considering the slumping failure expected in non-cohesive earthen embankments. Alternatively, TELEMAC-MASCARET, an open-source solver of free-surface flow developed by several European organizations, contains two modules, TELEMAC-2D/SISYPHE, which can simulate morphodynamic changes in floodplains. The current work aims to compare the simulation of the breaching process in dams due to overtopping by TELEMAC-2D/SISYPHE with that of the slumping model, considering the breach measurements of the Upper Rocky Ford dam that failed during the historic October 2015 flood in South Carolina. The evolution of breach shape in time and space after a prespecified failure time is compared. The results indicate that the predictions of the slumping model compare better with the field results than those made by TELEMAC-2D/SISYPHE. This work paves the way to investigate the feasibility of integrating the slumping model with open-source software for better prediction of embankment breaching and, consequently, flood propagation.