Sea levels analysis and surge modelling during storm Xynthia

International audienceIn 2010, during the night of 27–28 February, storm Xynthia crossed France and caused major damage. Sea level and sea state measurements available at SHOM (French Hydrographic and Oceanographic Service) were analysed to characterise the event. Sea level return periods during the storm along the Atlantic and the Channel French coasts were estimated from comparison between sea level measurements and extreme sea levels statistically computed. Surges in La Rochelle were modelled taking into account phenomena generating the surges (atmospheric pressure, wind and waves). Thus, sea level rise due to waves, the wave set-up, was modelled. Simulations were computed by WaveWatch III and HYCOM. The modelled surges from 20 February to 1 March have been compared to observed surges in La Rochelle during the same period in order to evaluate their accuracy