Pan-European assessment of coastal flood hazards

Abstract. Coastal flooding is among the most damaging natural hazards in Europe, yet large-scale assessments have typically relied on simplified static "bathtub" models and coarse elevation data. Here, we present a novel pan-European methodology that applies a dynamic flood model (RFSM-EDA) at 25 m resolution, forced by location-specific total water level (TWL) hydrographs. These hydrographs integrate mean sea level, tides, storm surge, and wave setup with spatially varying foreshore slopes, allowing storm type, duration, and shape to be explicitly represented. More than 51,000 coastal target points were used to reconstruct events, and the methodology was validated against 12 historical floods across diverse coastlines. Sensitivity analyses quantified uncertainty from model selection, DEM resolution, hydrograph shape, and storm type. Results show that static flood models systematically overestimate inundation, with errors exceeding 25 % in low-lying coastal floodplains such as Belgium and the United Kingdom. At the continental scale, storm type variability explains 41 % of flood map uncertainty, while hydrograph shape has a smaller but measurable effect. Including coastal protection standards reduces the estimated exposed floodplain by more than half, underscoring the critical role of defenses. By bridging the gap between global static assessments and local dynamic models, this study establishes a methodological benchmark for continental-scale flood hazard mapping. The framework not only advances scientific understanding of large-scale coastal flooding but also provides actionable evidence to support the EU Floods Directive, adaptation planning, and climate risk management in the finance and insurance sectors.