Nature-Based Coastal Protection in the Netherlands

The Netherlands is a low-lying country prone to inland and sea flooding. Sea level rise and
increasing flood risks require constant upgrading of flood protection infrastructure. The Hondsbossche Dunes are an example of a nature-based coastal protection solution addressing these needs.

Constructed after a section of the existing sea dike no longer met Dutch flood safety standards, stakeholders decided that instead of raising the dike, they would build an artificial beach and dune landscape to bolster the existing seawall. Stretching along 7 kilometres of the Dutch North Sea coast between the villages of Petten and Camperduin, the dunes are designed to withstand 1-in-10,000-year storm surge conditions and to resist sea level rise for 50 years.

In partnership with the International Association of Dredging Companies (IADC), we assessed the impact of the Hondsbossche Dunes. While we did not have exact data on potential flood area, our assessment assumes that the dunes protect more than 900 hectares of land, of which more than 60% is used for agriculture.

The beach resort town of Petten is the community most likely to be significantly impacted by flooding, the construction of the dune had a significant impact on the lives of 3,000 residents, not to mention the impacts on other nearby communities and rural areas. There are also considerable impacts for nature and recreation. The beach and dune landscape provides diverse habitats for plants and animals and has other biodiversity impacts, as well as new bike and walking trails.

Our assessment found that:

• The sand dunes increase the present value of tourism revenue by almost EUR 203 million over 50 years, while the grey alternative would have boosted by EUR 103 million.
• Even though the sand dunes require more maintenance, their lower construction costs and positive effect on tourism make them the better investment.
• The sand dunes offer future policy-makers significant flexibility to respond to dramatic changes in climate and sea level because they will be able to strengthen the flood protection without the type of reconstruction that would be necessary for traditional infrastructure.
• The sand dunes offer cost-effective flood protection. Over a 50-year horizon, the sustainable net present value (S-NPV)1 of the NBI is positive even when there is no flood and reaches EUR 98.27 million when assuming that the dunes prevent one flooding event. Conversely, the grey alternative would need to prevent two floods to have a positive S-NPV. This is because the dunes are cheaper to build and provide more benefits besides flood protection.