Extreme flood and storm impacts propagation: Multi-event evidence of cascading disruptions and interdependencies across critical entities’ sectors. 

Extreme storms and floods increasingly act not as isolated hazards but as systemic disasters with effects that propagate through interconnected networks of critical infrastructure, generating cascading technological, environmental, and societal disruptions. Within the framework of the new EU Critical Entities Resilience (CER) Directive, which defines eleven essential critical sectors, there is still limited understanding of how flood-storm events trigger cross-sector impact chains rather than single-infrastructure damage.This work studies multiple European extreme events to identify how impacts propagate across CER sectors, highlighting interdependencies between them. Using a harmonised database of documented disruptions derived from field surveys, scientific publications, operator reports, official bulletins, and post-event studies, impacts are classified in categories and mapped as interdependent impact chains linking energy, transport, water, wastewater, health, digital communications, public administration, food production, and other sectors.Across extreme events, consistent cascade patterns emerge. Flood- and landslide-induced damage to transport corridors and electricity distribution repeatedly initiates secondary failures in drinking-water supply, wastewater treatment, hospital functionality, telecommunications, food processing, and emergency response. Water-system failures in turn drive public-health crises through environmental contamination and epidemics, while dam damage and long-term inundation propagate into agricultural collapse and food-supply disruption. Environmental effects extend the footprint of disasters beyond flooded areas and have the potential to persist long after waters recede. Evidence shows that even when inundation is spatially limited, networked dependencies allow service outages and socio-economic impacts to spread regionally or nationally.The results demonstrate that energy, water, and transport repeatedly function as dominant cascade initiators, while they stand together with health, food, public administration, and digital services acting as cascade effect receivers. These findings imply that CER-based risk assessments must move beyond single-sector exposure mapping and classic flood hazard simulation towards a more dependency-aware analysis of cross-sector failure pathways, enabling more realistic preparedness, and resilience planning under a changing climate.