Modélisation du transport particulaire dans le Golfe du Lion en vue d'une application au devenir des traceurs radioactifs issus du Rhône

Among the contaminants introduced into the environment, the artificial radionuclides appear particularly important to take into account because of their chemical toxicity and/or of their radiotoxicity. Some radionuclides present a high affinity with particles so that the study of the sediment dynamics is a useful preliminary to the study of their dispersion on the open sea. This thesis is focused on the fate of sediments in the Gulf of Lions (NW Mediterranean) and in particular on the impact of the Rhone River, which is the main source of particulate matter in the Gulf of Lions. In order to study the sediment transport mechanisms on various space and time scales, this thesis is based on mathematical modelling. The hydro-sedimentary model set up in the Gulf of Lions, which takes into account the gathered effect of waves and currents, was supported by recent hydro-sedimentary data analyses. The CARMA (winter 2006/2007) and SCOPE (winter 2007/2008) experiments were used to better understand the physical processes that control the sediment transport on the Rhone prodelta and to validate the model. The period of the centennial Rhone River flood of December 2003 was also simulated in order to determine the impact of such extreme events on the fate of sediments. Both observations and simulations of the studied periods highlight the high capacity of erosion and transport induced by south-eastern storms on the prodelta.