CONTRIBUTIONS OF HUMAN ACTIVITIES AND NATURAL (EXTREME) EVENTS ON THE SEDIMENT DYNAMICS IN THE GULF OF LIONS

The Gulf of Lions (GOL) is a continental shelf ecosystem located in the NW Mediterranean Sea (SW France) where environmental, economic and societal issues are concentrated. As a highly valuable ecosystem, the challenging issue is to reach a Good Environmental Status (e.g. “good” hydrographical conditions), according to the EU Marine Strategy Framework Directive (MSFD). This study aims to quantify the relative contributions of natural extreme events and human activities to turbidity and suspended solids concentrations, one of the descriptors selected by the MSFD. The MARS3D hydrodynamics and sediment transport model is implemented and validated in the study area by in situ measurements and remote sensing ocean color data. Extreme storm events can significantly erode and resuspend sediments even in deep areas (>50m), with SSC ranging from 100mg/l near the bed and up to 10mg/l within 10m above the bed. These SSC values will be compared with trawl-induced resuspension simulated with the model. The effect of water resources management policies and their impact on river discharges will be also evaluated in term of plume dynamics.