Marine sand supply and Holocene coastal sedimentation in northern France between the Somme estuary and Belgium

From the Somme estuary to Belgium, much of the French coast is characterized by aeolian dunes, sand-choked estuaries and nearshore sand banks. The lack of sand-bearing rivers in this area and the abundance of sand in the English Channel point to the latter as the source of this important sandy accumulation. A comparison of patterns of nearshore and coastal accumulation with results from studies of the hydrodynamics and marine sand transport pathways suggests long-term drift of sand towards the French coast and the North Sea in response to tidal hows and meteorological forcing. This has occurred through sand bank migration onshore, and sand transport alongshore in a pathway hugging the French coast. From this tide-driven 'conveyor belt', fine sand moved onshore to form aeolian dunes, while sand of all sizes has accumulated as thick estuarine fill. This mode of Holocene coastal development emphasizes the joint action of tidal currents, storm waves and wind activity, within an overall framework of tidal dominance in this macrotidal setting.