Accumulation and dispersion dynamics of mud and sand particles in a continental shelf under estuarine influence: a numerical modelling analysis (Gironde, France)

Coastal environments are directly influenced by terrigenous inputs coming from rivers through estuaries. Quantifying the amount of nutrients and contaminants brought by sediments from continental areas to the sea is of major interest for marine resource protection. The complexity of the intra-estuarine dynamics, associated with the strong variability of meteorological forcing makes it difficult to quantify the residence time of particles within the estuary and the accumulation and dispersion areas offshore the mouth. Moreover, the dynamics of fine sediment trapping areas in the adjacent continental shelf (e.g. temporary or permanent storage such as the “West-Gironde Mud Patch” (WGMP) ) remains extremely challenging to address. Based on a realistic process-based numerical model, the aim of this work is to investigate the dynamics of the sediment accumulation and dispersion areas in order: (i) to describe the role played by the intertidal mudflats and the subtidal mud patches on sediment trapping and further resuspension, and (ii) to investigate the influence of hydro-meteorological events (e.g. high/low river discharges, storms) on sediment fluxes