Andromachi Sarantopoulou

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.

The growing complexity of human systems and the increasing frequency of climate-driven hazards have transformed some disasters from isolated events into cascading phenomena which propagate through critical infrastructure networks, disrupting essential services and amplifying systemic risk. This work examines the impacts of extreme storms and subsequent flooding on critical entities as defined under the new EU Directive (Critical Entities Resilience, CER). This study introduces a structured Critical Entities Disruption Database—Greece (CEDD-GR), as a methodological framework for systematically recording and analysing disruptions to critical entities, and applies it to the case of Storm Daniel (2023), one of the most severe flood events recorded in Greece. The analysis identified direct impacts across eight of the eleven sectors defined in the CER Directive, namely, energy, transport, health, drinking water, wastewater, public administration, digital infrastructure and food production, processing and distribution. A total of 21 different types of critical entities were documented, revealing the mechanisms through which failures affected different subsectors. The results underscore the systemic fragility of critical entities when exposed to extreme storms, compound flooding, and mass wasting processes (landslides, ground subsidence) and highlight the need for integrated resilience planning in line with the CER framework.

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.

Co- and post-seismic earthquake-induced hydrogeological anomalies (EQHAs) in Greece are mainly associated with moderate to strong earthquakes (M_w = 6.0–7.0), particularly when seismic intensities reach IX or above. The highest frequencies are observed in the Peloponnese and Ionian Islands, followed by Central Greece and the North Aegean, characterized by dense faulting and frequent strong earthquakes. EQHAs are classified into six main types, with hydraulic variations being the most common. About 77% of earthquakes produced only one or two types of EQHA, suggesting localized hydrogeological effects, while only a few induced multiple types. Strong events (M_w = 6.0–7.0), often historic, generated the broadest variety, highlighting the influence of local geological, hydrological, and tectonic conditions on magnitude alone. Springs and wells, representing 81% of the cases, dominate the affected systems, while lakes and rivers respond less often but significantly. Most EQHAs occur in Greece’s second seismic hazard zone (74%) due to its larger geographic area. EQHAs primarily develop in karstic and porous formations but also appear in impermeable rocks due to fracturing or karst. Larger earthquakes trigger anomalies at greater distances (>100 km). Though rarely fatal, EQHAs can damage water infrastructure, contaminate supplies, and cause shortages, underscoring the need for systematic monitoring and post-earthquake water resource management.

In early 2025, the Santorini–Amorgos area (Aegean Volcanic Arc, Greece) experienced a seismic swarm, with dozens of M ≥ 4.0 earthquakes and a maximum magnitude of M = 5.2. Beyond its seismological interest, the sequence was notable for triggering rare increased preparedness actions by Greek Civil Protection operational structures in anticipation of an imminent destructive earthquake. These actions included (i) risk communication, (ii) the reinforcement of operational structures with additional personnel and equipment on the affected islands, (iii) updates to local emergency plans, (iv) the dissemination of self-protection guidance, (v) the activation of emergency alert systems, and (vi) volunteer mobilization, including first aid and mental health first aid courses. Although it was in line with contingency plans, public participation was limited. Volunteers helped bridge this gap, focusing on vulnerable groups. The implemented actions in Greece are also compared with increased preparedness during the 2024–2025 seismic swarms in Ethiopia, as well as preparedness before the highly anticipated major earthquake in Istanbul (Turkey). In Greece and Turkey, legal and technical frameworks enabled swift institutional responses. In contrast, Ethiopia highlighted the risks of limited preparedness and the need to embed disaster risk reduction in national development strategies. All cases affirm that preparedness, through infrastructure, planning, communication, and community engagement, is vital to reducing earthquake impacts.

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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.

This research provides a detailed analysis of earthquake-triggered landslides (ETLs) in Greece, spanning from antiquity to the present, with an emphasis on their temporal, spatial, and statistical characteristics. Supported by published scientific sources and geographic information systems (GIS) tools, we detected 673 landslides triggered from 144 earthquakes in Greece. With 166 ETLs associated with historical earthquakes and 507 with recent ones, the analysis reveals that regions in western Greece, including the Ionian Islands and the Peloponnese, exhibit the highest ETL frequencies, a trend strongly related to their seismotectonic regime. Most ETLs have occurred in geotectonic units belonging to the External Hellenides. Limestone-dominated lithologies and post-alpine deposits were identified as particularly susceptible to ETLs. These are strongly associated with earthquakes with magnitudes ranging from 5.5 to 7.0. Rockfalls constitute the most frequent type of ETLs in Greece, accounting for nearly half of all documented events. Coastal and offshore landslides, though less frequent, still pose unique risks for Greece. ETLs have mainly been observed in the very high and high susceptibility areas. The impacts of ETLs on both natural and built environments are profound, with destruction of buildings and infrastructure exacerbating the public health impact and socio-economic toll of such events.