Storm Impact on a French coastal dune system: morphodynamic modeling using X-beach
Résumé
Dune breaching can play a significant role in flooding events, as illustrated for instance by the Xynthia event which hit the French Atlantic coast in February 2010. The presentation will focus on the breaches which occurred on the dune of Les Boucholeurs site (South of La Rochelle, France) during Xynthia. To investigate the morphological changes of the dune system induced by the hydrodynamical and morphodynamical processes, we use the XBeachmorphodynamical model (Unesco-IHE, Delft University and Deltares,Roelvink et al, 2009). The model results show that the morphological impacts were mainly due to the dune system overflow at flood and ebb tides.In this modeling experiment, only the locally generated infragravity waves were taken into account. These local infragravity waves have a negligible effect on dune breaching. Additional computations at the scale of the Pertuis show which infragravity waves are neglected in the local computations. In addition,a sensitivity analysis to the initial topography data is carried out to assess if the modeled breaches locations are determined by the initial topography structure.