The use of a micro-scale index to identify potential death risk areas due to coastal flood surges: lessons from Storm Xynthia on the French Atlantic coast

Abstract

Storm Xynthia (February 2010) was responsible for a large sea surge along the French Atlantic coast. It resulted in the flooding of low-lying coastal areas during the night. Urbanized areas were impacted and 41 people died by drowning in their homes. The location and type of construction of the houses in the affected area contributed to the death toll. The fact that the inadequacy of construction with regard to coastal flood hazard could lead to death was one of the most important lessons of the storm. The French government decided to buy back and scrap the most dangerous buildings hit by Xynthia. In order to prevent future deaths by drowning, we have developed a tool (the V.I.E. index) to identify houses where a risk of death due to a coastal flood cannot be excluded. The goal is to propose individual-based solutions for risk mitigation of residential houses. This tool uses a micro-scale-level analysis along with four criteria: (1) the potential water depth per house, (2) the distance between the dike and the house, (3) the architectural typology and (4) the closeness to rescue point. The methodological background and the first results for three towns are presented in this paper. Limitations and further developments are also discussed.