Beach nourishment and sedimentary plumes in the bay of Aigues-Mortes (Languedoc-Roussillon, France). Storm impacts on sedimentary hydrodynamics.

In the bay of Aigues-Mortes, the managers of the co astal cities try to preserve the socio-economic and patrimonial stakes against the coastal hazards, such as contami nation, storm surge and erosion. In this context, a massive beach nourishment of sand (1 million of m 3 for 10km of coastline) was made at the beginning o f year 2008 to reduce erosion. The REPBAM project (REchargements et Panaches sedimentaires dans la Baie d'Aigues-Mortes) aims to qualify and quantify by in-situ measurements and numerical modelling: 1. the geomorphological evolution of this mo dified coast and 2. the impact of the sediment's resuspension on the coastal ecosystems, in particular the one of t he Posidonia oceanica seagrass. A numerical modelling "wave/current/sediment" is first implemented for December 2008. Nested and curvilinear grids allow a very high resolution for the beach area but also include the inner shelf where the seagrasses are located. Hydrodynamic and topo-bath ymetric measurements were acquired from January to May 2012. Model and measurements results show the same trends during storms: strong currents, seaward migration of the inner bar, sediment resuspension and turbid on the inner shelf.