Numerical and Experimental Modeling of Levee Breach Including Slumping Failure of Breach Sides

Abstract

The overtopping failure of noncohesive earthen levees was investigated by considering sediment transport by flowing water and including slumping failure due to slope instability. The breach-shape evolution and breach hydrograph were measured during laboratory experiments. The experiments were performed with different inlet discharges and downstream boundary conditions. Detailed levee breach experimental results are presented, which may be used by other researchers to verify their computer models. A two-dimensional, finite-difference numerical model was developed, which solves the shallow-water equations along with the sediment-mass-conservation equation, in which a new source term is included to account for slumping failure. First, the hydrodynamic part of the model was validated against a steady flow through a levee breach. The predicted and the measured results are in good agreement in terms of the water depth and flow velocity within the main channel and the breach area. Then, the numerical model, which includes the modified sediment-mass-conservation equation, was validated by comparing the results with the test data of overtopping failure of a noncohesive earthen levee. The model successfully predicted the breach characteristics (i.e., breach-shape evolution and breach hydrograph). Moreover, a sensitivity analysis was conducted to study the effects of different model parameters on breach shape. It was observed that the breach dimensions (i.e., top width and maximum depth) are directly proportional to the Manning roughness coefficient and to the coefficient of the Meyer-Peter Müller formula. As the sediment repose angle increases, the breach top width decreases and the maximum depth of the breach increases.