The anticipated rise in extreme flood events in the Eastern Mediterranean region indicates an increase in significant societal impacts that have the potential to extend beyond the flooded areas and affect multiple sectors. Despite the criticality of understanding storm and flood risk and how they propagate in modern interconnected societies, the scope and complexity of storm- and flood-triggered cascading effects are still poorly comprehended. This study explores the effects created by the extreme Storm Daniel, occurring in Thessaly, Greece in 2023, aiming to gather new evidence on the types and scale of these cascading effects by analyzing its impacts in the region through fieldwork and official data collection. The results, as a contribution to existing knowledge on cascade effects, provide insights into the nature, the extent, the propagation mechanisms, and the consequences of these triggering events leading to diverse cascade effects. The study identifies the interactions between different phenomena following this extreme storm event to offer a better understanding of how impacts propagate, and therefore a better understanding of future challenges connected with this type of cascading hazards framework, ultimately contributing to predicting and mitigating associated risks.

As the frequency and severity of extreme weather events may increase due to climate change, understanding their impacts on water systems, resources, and infrastructure becomes very important. This study contributes to the growing body of knowledge on how extreme storms and floods disrupt interrelated elements comprising water systems by examining the case of Storm Daniel, which struck the Thessaly region of Greece in September 2023. Using a multi-source approach, including field data, institutional reports, scientific assessments, and publications, the study systematically identifies and categorizes the impacts of the storm and the ensuing flood across surface waters, drinking water supply, and wastewater infrastructure and other water-related systems through various mechanisms. The findings provide an overview of how such extreme storms may affect such systems and reveal widespread, interconnected disruptions that highlight systemic vulnerabilities in both natural and engineered systems, synthesizing these impact pathways. The study presents evidence of poor resilience against extreme events and climate change hazards in water-related infrastructure.

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.

Extreme floods and storms can disrupt essential services not just through direct physical damage but also through cascading effects across interconnected critical infrastructure. This study provides multi-event empirical evidence of how flood- and storm-related impacts propagate across sectors, using the sectoral classification of the EU Critical Entities Resilience (CER) Directive as an organising framework. The analysis examines 20 major European flood and storm events that occurred between 2002 and 2024. A harmonised database was developed from peer-reviewed studies, official reports, and post-event documentation. Documented disruptions were classified according to the eleven CER sectors and coded as direct source-sector and target-sector interactions. The final dataset includes 54 documented cross-sector cascading interactions, highlighting interesting patterns. Energy and transport were the dominant cascade-initiating sectors, accounting for 35.2% and 25.9% of all interactions, respectively. Health was the most frequent receiving sector, followed by public administration; digital infrastructure; drinking water; and food production, processing, and distribution. The study highlights the central roles of energy and transport as upstream drivers of disruption propagation, mainly through functional and logistical mechanisms. Overall, the findings show that in order to obtain a more realistic risk assessment, floods and storms should be understood not only as physical hazard events but also as potential systemic disruption processes. In addition, they suggest that critical-entity dependency mapping, scenario-based testing of upstream failures, and cross-sector continuity planning are crucial for CER-aligned risk assessment.

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The increasing frequency and severity of extreme storms and floods in the Eastern Mediterranean under climate change pose significant challenges for modern societies. These events often trigger cascading effects that extend far beyond the immediate disaster zone, disrupting interconnected systems such as power, transportation, and communication networks. Despite advancements in flood risk management and growing awareness of cascading hazards, the mechanisms driving these interdependencies and their broader impacts remain poorly understood. This study investigates the cascading effects triggered by the catastrophic Storm Daniel, which struck Thessaly, Greece, in September 2023, as a case study to explore the nature, scale, and ways of impact propagation.This work also provides an analysis of cascading effects, based on evidence on historical storm and flood disaster impacts in the Mediterranean region, identifying the interactions between primary hazards (flooding, landslides, erosion) and secondary consequences as well as the diverse sectors that suffer impacts. The analysis reveals different propagation mechanisms of these effects, highlighting the vulnerability of interconnected systems as well as the vulnerability of the natural and the built environment. The cascading effects identified underscore systemic risks of modern societies posed by extreme events, particularly in urban areas with dense, interdependent, and critical infrastructure.The findings contribute to the growing body of literature on cascading disasters, addressing critical knowledge gaps in understanding how extreme weather events propagate through modern societal systems. These insights are particularly relevant in the context of climate change, which is expected to amplify the frequency and intensity of such events.