LITTORAL SEDIMENTATION WITHIN SPARTINE AND OBIONE COMMUNITIES IN THE SOMME ESTUARY (EASTERN ENGLISH CHANNEL). PRELIMINARY RESULTS

Like many estuaries in the English Channel, the Somme estuary follows an infill pattern (Tessier et al., 2011). Land reclamation (embankments, polders) increase reinforces the natural accretion process (Bastide, 2011). The infilling leads to important modifications of environment uses (e.g. fisheries, navigation). The Somme estuary is macrotidal but wave-dominated due to high energy wave conditions. They induce strong littoral drift leading to the development of a gravel barrier at its mouth, on the southern part (Anthony and Héquette, 2007; Marion et al., 2009). The tidal regime is semi-diurnal and flood-dominated. The tidal range reaches 9-10 m in spring conditions. Fluvial discharge of the Somme river is weak (5-60 m3/s) (Dupont et al., 1994), inducing an infilling of the estuary almost exclusively with sands of marine origin (Dupont, 1981) and bioclasts from endemic benthic production (Desprez et al., 1998).