The Impact of Extreme Sea Level Rise on the National Strategies for Flood Protection and Freshwater in the Netherlands

This work investigates the impact of sea level rise (SLR) of up to 3 m on flood protection and freshwater availability in the Netherlands. We applied an exploratory modeling approach to consider the large degree of uncertainty associated with SLR. The results show the current degree of flood protection can be technically and financially maintained for up to three meters of SLR. A primary finding of this work is that a similar degree of safety against floods can be maintained. There are, however, several challenges: First, maintaining this degree of safety against floods requires considerable spatial allocations to maintain and upgrade flood defenses, often in populated areas with limited space. Second, the supply of sand for coastal nourishments will be challenging due to other functions in the North Sea (wind energy, shipping) and explosive remnants of war. Third, an acceleration in the rate of SLR may impact the overall feasibility of maintaining flood defenses. Maintaining the freshwater strategy will be challenging due to SLR-induced salt intrusion, which aggravates climate impacts including droughts. Continued flushing of salinized areas of regional water systems and polders with fresh river water will increasingly compete with other demands. Our analysis highlights the vulnerabilities of the flood protection and freshwater strategies and gives input to follow-up analyses on societal impact and perspectives of actions for adaptation.