Dernière mise à jour le : 8 novembre 2015

Non-hydrostatic modelling of extreme water levels on Banneg Island, France


Extreme water level events were observed during recent winters on Banneg Island [Ardhuin et al., 2011; Suanez et al., 2009], a small island off western Brittany well exposed to the large North Atlantic swells and characterized by steep rocky cliffs on its western part. Based on geomorphic evidences (bedrock scars, overturned boulders, debris lines) and hydrodynamic data, Fichaut and Suanez [2011] investigated the quarrying and transport of cliff-top storm deposits induced by giant wave events and partial flooding of the island (Fig.1), while Suanez et al. [2009] provided a retrospective analysis of extreme water levels based on a 30-year wave model hindcast and empirical run-up formula. Later, Sheremet et al. [2014] deployed pressure sensor measurements to this site and applied a 1D nonlinear mild-slope model to reveal that the highest water levels could exceed 6.5 m above the astronomical tide during major storms, mainly induced by large infragravity waves. In order to improve our understanding of the storm-induced hydrodynamics in the Iroise Sea, a wave buoy was deployed to the west of Banneg and additional pressure sensors were installed on the western part of the island (Section 2). In addition, a phase-resolving wave model based on the nonlinear shallow water equations, including non-hydrostatic pressure was applied to the study site and the model results were validated against in-situ observations (Section 3). The hydrodynamic data collected during the major storms of February 2014 were analyzed and the model was forced with the hydrodynamic conditions of the morning high tide of February 5, when some of the highest water levels were observed on the island (Section 4). Based on this combined model-data analysis, the incident and infragravity wave dynamics in the nearshore, and the associated sporadic flooding of the island were investigated in the light of previous studies on Banneg Island (Section 5)


keyboard_arrow_right Titre : Non-hydrostatic modelling of extreme water levels on Banneg Island, France
keyboard_arrow_right Type de documentation : Actes de colloque/congrès
keyboard_arrow_right Auteur(s) personne(s) : Autret Ronan, Fichaut Bernard, Ardhuin Fabrice, Leckler, Fabien , Suanez Serge, Dodet, Guillaume
keyboard_arrow_right Date de publication : 8 novembre 2015
keyboard_arrow_right Editeur(s) : JCOMM -Joint Technical Commission for Oceanography and Marine Meteorology
keyboard_arrow_right Tags thématiques : île, quantité résiduelle d'eau, niveau d'eau, gestion de la quantité d'eau
keyboard_arrow_right Mots-clés libres : niveau d'eau/île Banneg/archipel de Molène/hydrodynamique/tempête storm/water level/Banneg Island/hydrodynamic
keyboard_arrow_right Langue : Anglais
keyboard_arrow_right Collection : International Workshop on Wave Hindcasting and Forecasting and 5th Coastal Hazard Symposium

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