Coastline management in The Netherlands: human use versus natural dynamics

Abstract

The boundary between land and sea in The Nether- lands changes continuously. Every kilometre of the present position of the Dutch sandy coastline is the result of the interface between natural dynamics initiated by the sea and man-made action on land. Before 1990, each year ca. 20 ha of dunes disappeared through coastal retreat. In 1990 the Dutch government decided to stop any further long-term coastal recession and chose for 'dynamic preservation', which primarily aims at ensuring safety against flooding and sustainable preservation of the values and interests attached to the dunes and beaches. Five years later, a first review of the benefits and bottle- necks of the new coastal defence policy could be presented. The overall conclusion is that the 1990-choice for dynamic preservation was right. The considerable losses of dunes and beaches do not occur any longer. Sand nourishment is an effective method of coastline maintenance, which also serves the functions of the beach and dune area for human society. However, serious erosion of the deeper part of the shore- face threatens the coastline of the 21st century. Nearly a doubling of the nourishment volume is necessary to prevent a renewed landward shift of the coastline. An anticipated ac- celerated sea level rise (ca. 60 cm/century) will increase the sand losses by another 25 %. Plans are being finalized for large-scale land reclamation in front of the coastline as an answer to growing spatial problems on land. In other plans polders, now safely protected by sea dikes, will be returned to the sea in order to restore ecologically valuable salt marshes and mud flats. The position of the coastline will continue to change in the coming decades. Besides natural dynamics, human use of the coastal zone will certainly affect this process: measures to maintain the coastline at its 1990 position need to be seen in perspective: the coastline as a part of the coastal zone.