A Depth-Averaged 2-D Model of Non-Cohesive Dam/Levee Breach Processes

Abstract

A depth-averaged 2-D model has been developed to simulate the breach processes of non-cohesive dams and levees caused by overtopping flows. It solves the 2-D flow and sediment transport equations using an explicit finite volume method on a rectangular grid, with the HLL approximate Riemann solver to handle the mixed-regime flows near the breach. It considers interactions among transient flow, strong sediment transport and rapid bed change by including bed change and variable flow density in the continuity and momentum equations of flow. The model adopts the non-equilibrium approach for total-load sediment transport, and specifies different repose angles for the sediments below and above the water surface when handling the non-cohesive embankment slope avalanching. It uses a varying time step length that satisfies both the CFL condition and the limitation that the bed change is less than about ten percent of the local flow depth at each time step. The test using laboratory experiments shows the developed model predicts well the breach dimensions and flow characteristics.