UNDERWATER TROUGH NOURISHMENT AT TERSCHELLING ISLAND,THE NETHERLANDS

In order to maintain the stability of coastal dunes and beaches against increasing coastal erosion at the Terschelling island of The Netherlands, shoreface nourishment was implemented in the middle of the island from13.6 km to 18.2 km on November 5, 1993. 2.1 Mm³ of sands were nourished in the trough between two underwater bars, i.e. the most outside bar and the middle bar, and the average volume of nourished sand is around 450 m³/m per meter of width. Six months later, a new trough appeared again at the site of nourishment. However, the beach remained in stability for 8~10 years. The vertical movement of sediment decreased obviously. It is confirmed that trough nourishment may weaken the wave effect and transfer the sediments to the beachface to stabilize the coast and to broaden the berm automatically without damage of the sea-land pattern. It is worth to research and promote beach nourishment as such in the future.