Importance de l’âge des vagues et de la résonance sur le plateau continental : le cas de la tempête Xynthia, février 2010

• Main Authors: Bertin, Xavier, Bruneau, Nicolas, Breilh, Jean-François
• Format: Article in Journal/Newspaper
• Language: French
• Published: Paris : Société Hydrotechnique de France 2012
• Subjects: surcote; Xynthia; résonance; Pertuis Charentais; geo; envir; Le Plateau; North East Atlantic
• Online Access: https://www.persee.fr/doc/jhydr_0000-0001_2012_act_34_1_1233

The importance of the age of waves and of resonance on the continental shelf: the case of the Xynthia storm, February 2010. The Xynthia storm severely hit the coastlines of Charente Maritime and Vendée (central part of the Bay of Biscay) in the night between the 27th and the 28th February 2010 of February 2010. The associated storm surge exceeded 1.5 m in la Rochelle while being in phase with a high spring tide, causing the overall sea-level to reach the exceptional value of 8.0 m above marine chart datum. Numerous dykes and dunes were flooded or breached and large coastal areas were flooded. This study aims to improve understanding the physical processes responsible for this exceptional storm surge by means of numerical modeling. A modeling system coupling the codes SELFE (Zhang et al., 2008) and WWIII (Tolman, 2009) was implemented over the North-East Atlantic Ocean and resulted in tides and wave predictions with errors of the order of 1 to 2% and 15%, respectively. The storm surge was well predicted in the Bay of Biscay, with only a 0.1 m underestimation of the peak. The analysis of model results revealed that the storm surge was due mainly to the SW wind that induced an Ekman pumping, amplified by the presence of young and steep waves in the bay of Biscay. Such wave conditions are related to the uncommon track of Xynthia, which crossed the Bay of Biscay from SW to NE. The presence of 6-hour oscillations in both the measured and modeled storm surge was interpreted as resulting from a resonant phenomenon of the storm surge over the continental shelf. La tempête Xynthia a sévèrement touché les littoraux de Charente Maritime et de Vendée dans la nuit du 27 au 28 février 2010. La surcote associée a dépassé 1.5 m à la Rochelle et était en phase avec une marée haute de vives-eaux, si bien que le niveau de la mer a atteint la cote exceptionnelle de 8.0 m par rapport au zéro hydrographique. De nombreuses digues et cordons dunaires ont été submergés et se sont rompus et de larges territoires ont été submergés. Cette ...