Dutch experience with sand nourishments for dynamic coastline conservation – An operational overview

The Dutch coast is one of the most heavily nourished coasts globally. An average of 12 mln. m3 is annually added to the coastline of only 432 km for dynamic coastline conservation. This study provides an overview of the operational aspects of the more than 300 nourishments for coastline maintenance that have been performed since the 1990s and discusses the evolution of the nourishment approach and lessons learned with regard to the nourishment design. The first nourishments were beach and dune nourishments to repair local beach and dune erosion. In the 1990s the nourishment efforts increased when nourishing the coastline was set in policy as the formal strategy to dynamically preserve the coastline. Simultaneously shoreface nourishments emerged, which aim to feed the coast gradually over a longer period than beach nourishments. In 2001 the volume of sand used for nourishments increased from 6.4 to 12 mln. m3 per year, to enable the coastal zone to stay in equilibrium with sea level rise. Channel wall nourishments were introduced around that time because they can slow down the landward migration of tidal channels and can accommodate large volumes of sediment. Nowadays, underwater nourishments are preferred because of the lower costs associated, but the decision for a beach, shoreface, or channel wall nourishment also depends on the morphology, the local setting, and the purpose of the nourishment. All nourishments combined have succeeded in conserving the coastline at its desired position over the past 30 years.