Impact of a Major Storm on Sediment Exchanges between the Dunes, Beach, and Nearshore

The morphologic and volumetric changes of the dune foot, beach and inner nearshore zone over a major storm are studied on Egmond beach. The shoreline configuration of this beach showed an alongshore variation of embayments and horns, with an alongshore spacing between 400 and 700 m and a cross-shore amplitude of about 25 m. The response of the dune foot and intertidal beach was closely coupled to this alongshore variation, with major changes in the embayments (more reflective conditions) and small changes at the horns (more dissipative conditions). Overall, the upper beach and dune foot were eroding and flattened and the lower intertidal beach was accreting. The inner nearshore slope showed a steepening and a landward movement of e.g., the –3 m depth contour. The mechanisms that caused the changes are discussed and coupled to observed water levels in the nearshore These water levels altered and shifted the location of the transformed waves (asymmetric waves, breaking waves, bores and swash) in a cross-shore direction over the profiles.