Multi-Hazard Risk Assessment of Windstorms, Coastal and Riverine Flooding in France

Natural hazards are often interconnected. For example, severe storms can cause wind damage while simultaneously generating storm surges that can lead to coastal flooding. Specific weather systems, such as tropical and extratropical cyclones, can produce concurrent storm surge and heavy rainfall, resulting in compound flooding. When multiple hazards occur simultaneously or in close succession, they can cause substantially greater damage across sectors than if they occurred in isolation.

Despite this, traditional scientific risk assessments often focus on single hazards, limiting our understanding of interconnected natural hazards. In this study, we apply an existing multivariate statistical approach to model the spatiotemporal and multivariate dependence among the drivers of multi-hazard events. We choose France as a case study to look into the relationships between wind gust speeds (windstorms), extreme sea levels (coastal flooding), and high river discharges (riverine flooding). Based on the estimated dependence structure, we generate 10,000 years of synthetic multi-hazard events. These events are combined with existing high-resolution hazard layers to produce multi-hazard footprints for individual events. These event footprints are then overlaid with exposure and vulnerability data to estimate multi-hazard damage and risk. The resulting risk estimates provide improved insights for multi-hazard assessment and support more effective management of associated financial risks.