Beach-Dune Interactions in Nourishment Areas along the Dutch Coast

The impact of beach nourishment on the development of coastal dunes was studied along the Dutch coast. A database of annual cross-shore profiles was analysed to derive volumetric changes associated with aeolian and hydrodynamic processes. The database covered a period of 15 years. Beach nourishment projects that were carried out arbitrarily within this time-span were selected, and the volumetric changes occurring on the selected sites were statistically related to the number of years following nourishment. An overall negative sand budget was found for the supratidal zone of the nourished sites. A substantial part of the sand was blown to the foredunes. One year after nourishment, this amount increased significantly. At the same time, the supratidal beach was eroded more. In the second and third year after nourishment, the erosion of the higher parts of the nourishment decreased. In the foredune, dune toe erosion due to storm surges was usually negligible until the fourth year following beach nourishment. Thus, beach nourishment temporarily protected the adjacent foredunes from being eroded by periodic wave attack, and also temporarily enlarged the aeolian sand transport rate to the dunes.