| dc.description.abstract | In the Netherlands, sandy shores cover most of the coastline and are prone to erosion from the sea. As the coast, especially the dunes, forms the primary flood defence against the sea for the Netherlands, the shore is frequently nourished. The nourishments are also placed on the Wadden Islands, where along with waves influencing the coast, tidal processes too are an important morphological driver. An im-portant process at the Wadden Islands, which is a combination of tidal- and wave-driven processes is the cyclical attachment of shoals. Ameland is one of the Wadden Islands, heavily nourished and receiv-ing sand from attaching shoals approximately every 55 years. The effect the nourishments and shoals have on the shoreline dynamics of Ameland is not well understood. Using the Python toolkit CoastSat to extract shoreline positions from satellite images, this research has shown that the sand volume of the attached shoal moved mainly east, in lesser extend south, with a migration speed of 167 m/yr, and has reached to half the length of the island in 40 years. The beach nourishments were shown to have a half-life of 643 days, with the dispersion mainly moving cross-shore and not alongshore. The effect of the shoreface nourishments could not be discerned using the satellite imagery. The shoreface nourishments could have provided a lee-effect to the shoreline, reducing the wave energy and thus erosion without adding sand to the beach zone. The results show that Ameland can be divided into three zones, the west being dominated by tidal- and wave-driven alongshore currents and beach nourishments, the north and middle part are dominated by the sand input from the shoal being dispersed east by wave-driven along-shore. The eastern half of the island is dominated by shoreface nourishments, and the alongshore current from the west supplies sand from the shoal. | |
