2-D And 3-D Numerical Modeling Of Dam Break Waves Over Moveable Beds

Abstract

Dam-break waves over movable beds are multi-physical processes that involve rapidly varying flows, intense sediment transport and significant alteration in bed morphology. In turn, this change in morphology may strongly affect the maximum water levels and arrival time of the wave front, which are the main characteristics to consider for use in risk assessment. In this paper, we report numerical simulations of dam-break waves induced sediment transport using the open source Telemac-Mascaret modeling system (www.opentelemac.org). The 3D hydrodynamic model, TELEMAC-3D, and the 2D depth-averaged hydrodynamic model, TELEMAC-2D, are used. Both models are internally coupled with the sediment transport module SISYPHE. Bed load rate is calculated using empirical formula and bed geometry is updated using the Exner equation. We simulate a laboratory experiment of dam break waves over sandy beds performed at Université Catholique de Louvain (Belgium) in the framework of the NSF-PIRE project “Modelling of Flood Hazards and Geomorphic Impacts of Levee Breach and Dam Failure”. Comparisons between numerical results and measurements are based on the final bed topography after the passage of the wave as well as water level evolution recorded at selected gauging stations. Both numerical models provide reliable results: the water free-surface is accurately reproduced, with the 3D model yielding better results at the gauge stations located far downstream from the gate. Regarding the bed evolution, scouring around the location of the collapsed dam and sediment deposition further downstream are well captured, but magnitude of bed changes is underpredicted