URBAN DUNES: PROMOTING BWN DUNE FORMATION AT NOURISHED BEACHES THROUGH SPATIAL DESIGN

Abstract

Sandy shores offer a multitude of ecosystem services; regulating- (e.g. protection against flooding), production- (e.g. drinking water) and cultural services (e.g. recreation), all depending on the quality of supporting services (e.g. natural balances of water, nutrients and sediment). For sandy shores especially, the long-term physical existence is depending on the sediment balance. Therefore, based on Building with Nature (BwN) principles, sediment balances and -dynamics represent essential components of any spatial design of sustainable urbanized sandy shores. Examples of such design are nourishments where the sand balance of the system is amplified and natural dynamics distribute sediment ashore. This approach is used in the Netherlands to compensate for coastal erosion with a total yearly nourishment volume of 12 million m3 of sand. Typical magnitudes of individual nourishments are 1 to 2 million m3, whereas the Sand motor is an experimental mega nourishment of 20 million m3. After nourishment, the sediment is transported by natural processes (waves, tide, wind etc) contributing to the growth of dunes. The question is how to support this dune development, not just to improve the coastal safety, but also the combined use with other urban & ecological programs in the coastal zone. In this contribution we discuss spatial design principles and their influence on the transport of sediment for the formation of dunes; supporting flood safety, urban and landscape qualities. This requires an interplay of nourishment, directed sediment transport in the beach-dune interface and the desired buffer capacity established by the dunes. Depending on the preferred defence strategy (seaward, landward or consolidating) different spatial interventions can be made to enhance dune formation after nourishment.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/fNnVkDS1Gig