Extreme Wave Flood-Risk Mapping Within the Basque Coast

Abstract

The objective of this contribution is to describe the methodology and key results of an assessment of the impacts of extreme wave events on Basque coast (Gipuzkoan coast) via flood risk maps. The risk of marine flooding during extreme events has been calculated along the coast, by combining the action from high sea level and waves and using numerical modeling. The extreme wave flood level was integrated with a high-resolution Digital Terrain Model (using airborne topographic LiDAR) to produce flood-risk maps. The impacts on land use and biological communities have also been assessed by overlaying the flood-risk maps with detailed coastal habitat classification. The results were compared to the impact expected from sea level rise by the end of the 21st century. The extreme wave flood risk map suggests that 164 ha of the supralittoral zone of the Gipuzkoan coast will be affected. This area consists mainly in sandy beaches, harbours and urban areas exposed to high wave energy (NW orientation). In contrast the areas expected to be impacted by sea level rise, are concentrated in protected low-lying areas especially within the inner estuaries (with terrestrial and artificial habitats being the most affected) and extend over 111 ha.