Dam and Levee Failures: an Overview of Flood Wave Propagation Modeling

Dams and levees are hydraulic structures that are designed to resist to water pressure, but they occasionally break because of constructional defaults or unexpected events. When such a failure occurs, water can be suddenly released and create a flood wave more dangerous than natural events. Hydrodynamic modelling of such waves includes both estimating the flow hydrograph at the structure site and propagating the latter hydrograph downstream the structure. For engineering purposes, simplified erosion models are used to obtain the breach hydrograph for earthen embankments while instantaneous failure is often assumed for concrete structures. For flood wave propagation, 1-D or 2-D shallow water equations are solved using numerical schemes that can deal with supercritical and subcritical flow regimes. Uncertainty is likely to be high because it is difficult to calibrate the numerical model for flows much stronger than actual observations. Particularly, because of high velocities, sediment transport is likely to occur and to modify the risk parameters ; numerical modelling can help defining the range of uncertainty due to this sediment transport but calibration is even more difficult than for hydrodynamic modelling. The description of these latter models is illustrated on various events, the Malpasset dam failure that occurred in 1958 during the first filling, the 100 year flood in Agly coastal plain that resulted in levee breaching in 1999 and the Ha ! Ha ! Dam failure that caused huge geomorphological changes along the downstream valley.Paquier André, Goutal Nicole. Dam and Levee Failures: an Overview of Flood Wave Propagation Modeling. In: SimHydro 2014. New Trends in Simulation. 11-13 June 2014 Ecole Polytech’ Nice (France) 2014