Understanding Coastal Resilience of the Belgian West Coast

Topobathymetric monitoring carried out in the past 30 years revealed that the amount of sand in the active zone of the Belgian West Coast increased substantially. Correcting for sand works carried out, the rate of natural feeding of the area was estimated to be 10 mm/year, which is significantly more than the local sea level rise rate of 2 to 3 mm/year. One concludes that this coastal zone, with a length of ca. 16 km, has shown a natural resilience against sea level rise. The question remains which processes govern this behavior and where natural input of sand to the system occurs. Using available coastal monitoring data for the Belgian coast, as well as a state-of-the-art sand transport model, revealed that different processes drive a cross-shore natural feeding from offshore to the coastline. The spatial distribution of this cross-shore natural feeding is determined by the existence of a gully-sand bank system. The outcome of this research was a conceptual model for the large-scale sand exchange in the study area which is implemented in an 1D coastline model. The most important element in these models was the cross-shore natural feeding of the active zone via a shoreface connected ridge amounting to 95,000 m(3)/year in the period 2000-2020.