Michalis Vousdoukas, Lorenzo Mentaschi, Juan Carlos Ciscar, Jochen Hinkel, Philip J. Ward, Luc Feyen

Extreme sea levels (ESLs) in Europe could rise by as much as one meter or more due to climate change by the end of this century. Without adaptation measures, annual damages from coastal flooding in Europe could increase sharply from €1.4 billion nowadays to at least €90 billion by 2100. While damages will be lower than those figures as countries continue to protect their coast, there has been no dedicated European cost-benefit analysis of possible protective measures against rising seas. Here we present a first comprehensive analysis of economically efficient adaptation scenarios for Europe during the present century. We employ a fully probabilistic framework considering all major sources of uncertainty, as well as dynamic simulations of all future ESL components and inundation. We find that at least 83% of flood damages could be avoided by elevating dykes in an economically efficient way along the European coastline. This corresponds to 23.7%-32.1% of Europe’s coastline, specifically where high value conurbations exist. The mean benefit to cost ratio of such investment varies from 6.7 to 14.9, depending on the scenario and can even reach 30 for high-end greenhouse gas emission and socio-economic projections.