Coastal flood risk and adaptation strategies under deep uncertainty – a modelling framework

Coastal floods as a result of extreme sea levels are a major hazard along much of the world’s developed coastlines. To identify adequate adaptation strategies, accurate estimates of coastal flood risk are required. However, the frequency of extreme sea levels is expected to increase as mean sea levels rise. Combined with population growth, urbanization and economic development, there exist large uncertainties in the development of future flood risk. Addressing this challenge requires a close collaboration between a range of natural and social science disciplines and fields. The SEASCApe project (storm surges, sea-level rise and adaptation responses of the German Baltic Sea coast) presents such a collaboration. The project provides a modelling framework to address the coastal adaptation challenge for the German Baltic Sea coast, however the methods used may be applied to other regions worldwide. First, robust local scale information on coastal extreme sea levels is determined using statistical and numerical modelling techniques. This is done for present day and future sea levels. Next, this information is combined with detailed socioeconomic data for the entire coastline, and flood risk analyses are conducted using reduced complexity hydrodynamic models. Lastly, the resulting information is used to develop economic decision-support methods. These methods provide insights into efficient and robust flood protection levels for the German Baltic Sea coast.