Extreme sea levels under present and future climate

Abstract

Continental or global studies of coastal flood hazard in the context of climate change encounter several obstacles. The primary concern is the limited coverage of sea level data, especially the high-frequency sort needed to analyse sea level extremes. In this paper we present the calculations of return periods of storm surge heights and water levels for the European coast. The analysis utilized simulations using Delft3D hydrodynamic model driven by meteorological data with temporal and spatial resolution, created under EURO-CORDEX activities. The simulations were calibrated using short- and long-term sea levels from over 150 gauges. Annual maxima of water levels were extracted from five simulations: 1971–2000 historical run as well as 2021–50 and 2071–2100 simulations based on two emissions scenarios each. Spatially varying sea level rise projections were also included. Annual maxima were then fitted to probability distributions in order to obtain the return periods. The results were combined with more than 70,000 coastal sections, so that they would be complimentary with a river flood hazard dataset developed in parallel. The study showed a good match between simulated and observed storm surge heights. It also shows large differences in future trends of water levels in Europe.