Sediment transport over an intertidal mudflat: field investigations and estimation of fluxes within the "Baie de Marennes-Oleron" (France)

This contribution analyses the various hydrodynamic forcings responsible fo r sediment dynamics over the intertidal mudflat of Brouage (Baie de Marenne s-Oleron). This mudflat is characterized by a gentle slope and an extensive ridge and runnel network. The sediment dynamics have been thoroughly inves tigated by continuous measurements of turbidity, waves and tidal currents, core measurements and bed level monitoring. Turbidity measurements highligh t the importance of waves to the sediment resuspension over the mudflat. Co nversely, higher turbidities during spring tides in the channel, further of fshore, indicate the major contribution of the tide to sediment transport w ithin the embayment. Overall, a large amount of mobile sediment is consiste ntly present within the bay, either as suspensions during spring tides, or as fluid mud deposits in the runnels of the mudflat during neap tides. Resi dual sediment fluxes, computed from the measurements, proved to be onshore during spring tides, but offshore during periods of wave domination. Finall y, a sediment dynamics overview for the area is proposed on the basis of th e flux estimations. (C) 2000 Elsevier Science Ltd. All rights reserved.