New study compares costs of moving with sea level rise in the Netherlands

A new study published in Water Matters (PDF) presents a detailed assessment of the long-term costs of the adaptation strategy known as moving with sea level rise (in Dutch: meebewegen), as explored within the Dutch Sea Level Rise Knowledge Programme. The research focuses on the so-called hybrid approach, in which the Randstad continues to be protected by strong flood defences, while households and businesses gradually withdraw from low-lying and flood-prone areas elsewhere in the Netherlands.

The study translates the abstract concept of moving with sea level rise into concrete cost components, enabling comparison with other long-term strategies such as continued protection, building seaward, or growing with sea level rise. Costs are structured into implementation costs, flood damage costs, impacts on agriculture and drinking water supply, and broader socio-economic effects, including implications for inequality and the financial sector.

Several variants of moving with sea level rise are analysed, distinguishing between retreat through relocation or through adaptive building measures, and between scenarios where flood defences are maintained during the transition period and those where they are not. A key finding is that abandoning investment in flood defences during the transition leads to rapidly increasing flood probabilities and catastrophic economic risks well before the end of the transition period.

Across all variants, the societal costs of moving with sea level rise are found to be substantially higher than those of continuing current flood protection policies. The only variant that avoids catastrophic risk is one in which all homes and businesses are relocated from transition areas while flood defences continue to be strengthened during the transition. Even in this case, total costs are estimated to be around ten times higher than maintaining the existing water safety strategy, particularly as transition periods lengthen and distributional impacts increase.