Sustainable coastline management - the cumulative effects of 30 years of nourishments in the Netherlands

Coastal erosion threatens flood safety and other uses of beaches and dunes globally. In the Netherlands a coastline maintenance policy was implemented in the 1990's to address the negative effects of erosion, with sand nourishments as the primary means. In this study, the cumulative effects of these nourishments are evaluated against the strategic goal of sustainable preservation of the uses and values of the coast. This research aims to inform national and international policy makers, practitioners, and scientist about the possible long-term effects of coastal management with structural sand nourishments. Coastal indicators were analysed to quantify the morphological evolution of the coast before and since coastline maintenance. It is observed that regular nourishments serve to halt structural coastline retreat. The coastline built out, on average, which was necessary to achieve maintenance of the most erosive areas. Additionally, strong dune growth is observed since the start of coastline maintenance, thanks to wind-driven transport of nourished sand and more dynamic dune management. Nourishments thus contribute positively to flood safety, although flood safety is not an automatic benefit of coastline maintenance. Space for recreation and nature is maintained or improved: the dry beach width was unaffected, and dune areas have grown. Further, it is reported that the impact of nourishments on the coastal ecosystem is local and temporary, leading to the inference that uses and values of the coast are being maintained sustainably through regular nourishments. Overall, the approach of coastline maintenance with regular pro-active nourishments has thus proven to be successful. • The Netherlands successfully halted coastline retreat with sand nourishments. • Coastline maintenance resulted in dune growth and local seaward expansions. • The entire coastal zone is elevated but sediment is unevenly distributed alongshore. • Nourishments benefit coastal uses like flood safety, recreation, and dune habitats.