SEDIMENT AVAILABILITY AND CONCEPTUAL MODELS OF SAND BARS MORPHODYNAMICS FOR A MICROTIDAL BEACH (SèTE, FRANCE)

摘要

Two different approaches were performed on a microtidal beach in Sète (Mediterranean Sea, France). (1) Quantification of sand reservoir on the shoreface based on very high-resolution seismic data to assess the sand volume repartition and check the link with the littoral drift. (2) Displaying morphodynamics models for the bar changes. Results show that the volume increases in the longshore drift direction and become the highest downdrift, where erosion is the weaker. The morphological evolution of the sedimentary bars on the area can be synthesized according to two conceptual models in reaction to hydrodynamic variability. The two approaches finally contribute in a way complementary to a better knowledge of the littoral system behaviour and provide a new way to foreknow the beach vulnerability. For beach in erosion, all the sediment available can be removed during the bar changes. Furthermore, depending on the size of the total sand reservoir on the shoreface, the hydrodynamic forcing don’t seem to have the same impact on the beach and on the shoreface evolution.