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In November 2017, a high-intensity storm caused a catastrophic flash flood that devastated the city of Mandra, in Greece, and led to the tragic loss of 24 people. The storm caused flooding in the two main tributaries of the basin, creating two very similar hydrological responses with similar flood characteristics that hit two different environments: one within the city and one outside. This work examines the fatal incidents that occurred in relation to the characteristics of the surrounding environment, to investigate the role of the latter in flood mortality. Then, the analysis carried out for the 2017 flood is expanded to a broader database of flood deaths for Greece (1960–2018) for comparison. Results show that certain mortality characteristics differ substantially depending on the setting. Outdoor incidents are more abundant in nonurban environments, in which victims exhibit mostly an active or risk-taking behaviour against the imminent risk. Urban environments are characterised by a greater diversity of victim activities, higher percentages of indoor deaths, especially for older victims and more passive behaviours. Overall, the study presents evidence on how risk situations develop differently between urban and nonurban settings. Findings are relevant in shaping policy and education programs aiming to mitigate risk. © 2020 The Authors. Journal of Flood Risk Management published by Chartered Institution of Water and Environmental Management and John Wiley & Sons Ltd.

The spatial and temporal scale of flash flood occurrence provides limited opportunities for observations and measurements using conventional monitoring networks, turning the focus to event-based, post-disaster studies. Post-flood surveys exploit field evidence to make indirect discharge estimations, aiming to improve our understanding of hydrological response dynamics under extreme meteorological forcing. However, discharge estimations are associated with demanding fieldwork aiming to record in small timeframes delicate data and data prone-to-be-lost and achieve the desired accuracy in measurements to minimize various uncertainties of the process. In this work, we explore the potential of unmanned aerial systems (UAS) technology, in combination with the Structure for Motion (SfM) and optical granulometry techniques in peak discharge estimations. We compare the results of the UAS-aided discharge estimations to estimates derived from differential Global Navigation Satellite System (d-GNSS) surveys and hydrologic modelling. The application in the catchment of the Soures torrent in Greece, after a catastrophic flood, shows that the UAS-aided method determined peak discharge with accuracy, providing very similar values compared to the ones estimated by the established traditional approach. The technique proved to be particularly effective, providing flexibility in terms of resources and timing, although there are certain limitations to its applicability, related mostly to the optical granulometry as well as the condition of the channel. The application highlighted important advantages and certain weaknesses of these emerging tools in indirect discharge estimations, which we discuss in detail. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Flash floods cause some of the most severe natural disasters around the world. The extensive diversity and discontinuity of flash flood impacts, which are controlled mostly by surface properties, lead to major difficulties in obtaining a holistic appraisal and a realistic overview of flash flood effects and their severity and make predicting future impacts a significant challenge. Current practices of describing flood impact severity use a limited set of criteria and assign a qualitative characterization (e.g. major, catastrophic, etc.) to each event. The present study proposes an approach that provides a coherent overview of these effects through the classification of impact types and severity and for the first time mapping their spatial extent in a continuous way across the floodplain. To this end, the flood effects are grouped into 4 categories depending on the affected elements, namely: (i) impacts on built environment (ii) impacts on man-made mobile objects, (iii) impacts on the natural environment (including vegetation, agriculture, geomorphology, and pollution) and (iv) impacts on the human population (entrapments, injuries, fatalities). Each of the four above categories is classified in a system of 10 severity classes that are defined with a logical order of increasing importance of damages forming a severity scale. The scale's application is tested on a catastrophic flood event of 2017 in Mandra, Greece, with a well-described and wide range of impacts, including 24 fatalities. The application allowed the development of high-resolution impact-severity maps that revealed interesting damage patterns and highlighted high severity areas. The resulting maps offer insights on future impacts and indicate a potential to provide the groundwork for targeted prevention measures as well as correlations of impact severity with hydrological aspects of flooding. © 2020 Elsevier B.V.

On November 15, 2017, a high intensity convective storm, reaching 300 mm in 13 h in the core zone of the event, hit the western part of the region of Attica in Greece, causing a catastrophic flash flood in the town of Mandra and a tragic loss of 24 people, making it the most deadly flood in the country, in a period of 40 years. The research team surveyed the area during and after the flood using a combination of systematic ground and aerial observations with the aid of an unmanned aerial vehicle (UAV), aiming to reconstruct the basic physical and hydrological characteristics of the flood and its impacts. The analysis produced detailed flood extent and depth maps that provided a comprehensive description of the physical characteristics of floodwaters across the inundated area. Peak discharge was estimated, using a UAV-derived digital surface model, at two locations, corresponding to the two main tributaries and indicated an impressive hydrological response, between 9 and 10 m3/s/km2. Impact analysis on the basis of these observations showed an extensive diversity, including effects in geomorphology, vegetation, buildings, infrastructure and human population. Analysis of meteorological, botanical and geomorphological evidence lead to the conclusion that this flash flood was a very rare event. Results demonstrate that the combination of aerial and ground observations allow an enhanced and holistic reconstruction of a flash flood and its impacts with high accuracy, leading to the conclusion that the approach used has a significant potential in many aspects of flood disaster investigations. © 2018 Elsevier Ltd

Urban flooding is a gradually increasing problem as the urban population expands into floodplains. In urban environments, flood vulnerability is significantly increased as a more concentrated population and assets makes flooding costly and challenging, in terms of impact estimation. This work focuses on mapping and classifying impacts after the catastrophic 2014 flood in Athens, Greece. The study proposes a method for classifying flood effects into four categories including: the natural and built environment, mobile objects and human population, organized in five classes of increasing severity, i.e. minor, weak, moderate, strong and extreme. Flood effects are grouped based on the qualitative nature of the recorded effects, allowing the development of an impact-severity map. Mapping of the 2014 flood effects indicated specific locations where the severity of impacts was distinctively higher than others, providing a holistic overview of the flood’s effects and highlighting the usefulness of the approach in future flood protection planning. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

This work focuses on the analysis of flood fatalities in Greece, between 1970 and 2010. To this end, the paper develops and studies a systematic record of 151 flood-related fatalities that occurred across the country during this period. Based on this inventory and detailed incident reports, a database is developed, to examine the temporal, spatial and seasonal distribution of these incidents and the circumstances under which they occur. Analysis indicates that fatalities present a strong seasonality but show no particular temporal trends. Fatal incidents occur mostly during nighttime, outdoors and in rural areas of the country. Vehicle-related deaths are the most common type of incident, regarding the activity of victims, whereas other outdoor and indoor types of incidents present smaller percentages. Drowning was found to be the most common etiology of death. Males and elderly individuals showed proportionally higher representation, indicating an increased risk of these population groups to flooding. © 2015 The Chartered Institution of Water and Environmental Management (CIWEM) and John Wiley & Sons Ltd

For the first time flood mortality is analysed and compared between a Western (Portugal) and an Eastern Mediterranean country (Greece). Flood fatalities are examined and compared in terms of frequency, temporal evolution, spatial distribution, deadliest flood types, gender of the victims, circumstances surrounding fatalities, and individual and societal risk. A common flood fatalities database was formed for the period 1960–2010 by merging the DISASTER database for Portugal and the Greek database Individual flood cases generated more deaths in Greece than in Portugal (excluding an outlier flash flood event in the latter). Despite some fluctuations evidence of a gradual decrease in fatality numbers were recorded for both countries. Since the 1980's the number of flood cases with multiple fatalities has been gradually declining, due to changes in qualitative characteristics of mortality. Flood fatalities predominantly occur during autumn in Greece and during winter in Portugal. In both Greece and Portugal flash floods were responsible for more than 80% of the total mortality. The main metropolitan areas of each country were found to be hotspots of flood mortality; a trend connected, with the higher population density along the coastal areas combined with the expansion of urban fabric towards flood-prone areas. Gender distribution of fatalities indicates that males are more vulnerable in both countries. The circumstances surrounding fatalities showed that fatalities occurring inside buildings have been gradually reducing in time, while vehicle-related deaths have been rising, showing that individuals hold an active role when they voluntarily enter in floodwaters during a flood. © 2017 Elsevier Ltd

Even though numerous methods have been developed to predict the vulnerability of urban areas to flooding, there is still room for improvement in determining the susceptibility of individual buildings. This work aims to identify characteristics that affect a building's probability to suffer flooding and evaluate their influence. The study uses Google Street View to examine 1073 buildings known to have flooded after an extreme precipitation event in 2013 in Athens, Greece and to compare them with characteristics of buildings that did not experience flooding. Using logistic regression, this work investigates the influence of these elements. Results show that certain characteristics of buildings increase their probability to flood up to 4.1 times. The study develops an equation involving all influential elements able to predict the buildings that will suffer flooding on a 77% rate. © 2017 Elsevier Ltd

This work studies the influence of various factors on the spatial distribution of flash flooding in urban areas. It examines an extreme precipitation event that occurred in 2013, in Athens, Greece, causing flooding and damages in various parts of the city. GIS was used to determine the values of potentially flood-influencing parameters, while logistic regression was used to examine the statistical correlation between their values and the respective values at the locations of 1138 flooded buildings. Statistical significance and other metrics were used to measure the influence of these factors on the distribution of flooding. Results showed that certain factors, including the degree of soil sealing, accumulated rainfall, slope and others, influence the distribution of flooding to significantly different degrees. Incorporation of building characteristics into the regression model increased further its coherence. The study showed a strong relationship between a combination of factors and flood occurrence with R2 reaching 0.63 and a prediction accuracy of 82.9%. The degree of soil sealing and slope were the most influential in determining the distribution of flooding. However, when building parameters were incorporated, the level of a building's lower opening in comparison with ground level was by a significant margin the most important parameter. © 2016 Elsevier Ltd.

Purpose: Tropical storms pose a significant threat to population despite the noteworthy improvements in forecasting and emergency management. Following the effects of Hurricane Sandy in the continental North America (USA and Canada) and the Caribbean, the purpose of this paper is to examine the mortality caused by the hurricane, focussing on differences in human vulnerability between these two regions. Design/methodology/approach: The authors developed a database of 233 deaths, consisting of variables that provided a description of the circumstances under which the fatal incidents occurred and demographic details of the victims. Findings: Analysis of the database showed higher percentages of female and young victims in the Caribbean than in continental North America, where mortality increased progressively with age and the ratio of males to females was higher. The majority of deaths occurred outdoors especially during clean-up and in vehicle crashes related to the storm. Physical trauma and drowning were identified as the most common causes of death, followed by carbon monoxide poisoning, hypothermia and others, although substantially different percentages were recorded between the two regions. Overall, indirect deaths presented a higher percentage than direct ones. Among the latter, incidents caused by storm surge and tree falls showed the highest numbers. Power failure and car crashes were the most common cause of indirect incidents. Originality/value: The paper provides a thorough analysis of the circumstances under which fatal incidents occurred. It identifies parameters that affected the vulnerability of human life to the storm and discusses the differences between the Caribbean and continental North America. © Emerald Group Publishing Limited.

This work focuses on the analysis of vehicle-related flood fatalities in Greece, in an effort to provide a better understanding on the circumstances under which they occur. Therefore, an inventory of 60 fatalities associated with the use of vehicles, induced during 37 flood events between 1970 and 2010, was studied. To this end, we developed a database consisting of variables that provided a systematic description of the circumstances under which each incident occurred, including details of the surrounding environment, the road infrastructure, specifics on the incident and demographic details of the involved individuals. Analysis showed an increase in vehicle-related cases over the period of study, with the majority of the incidents occurring after 1990. Males, and individuals between 40 and 69 years old, showed an increased representation among both the drivers and the victims, although the latter showed an overrepresentation of young individuals as well. Most events occurred during nighttime and in rural areas of the country. With respect to the surroundings, most cases occurred on paved road network and bridges that proved vulnerable to flooding phenomena. In a significant number of cases, fatal incidents occurred on paved river crossings, constructed on the riverbed of usually dry torrents or waterways. Drowning was found to be the primary cause of death. Analysis of the drivers actions, exactly before the incident, showed that in the majority of occasions, they chose to enter into flooded areas, either to travel across or to save someone, or recover something. In some cases, vehicle occupants found themselves in a hazardous position when floodwaters rose unexpectedly, giving them no chance to avoid danger. It was therefore found that drivers, pursued an active, rather than a passive, stance in the majority of incidents, attributed, in certain occasions, to an underestimation of risk. © 2013 © 2013 Taylor & Francis.

The Sparta Fault system is a major structure approximately 64 km long that bounds the eastern flank of the Taygetos Mountain front (2407 m) and shapes the present-day Sparta basin. It was activated in 464 B.C., devastating the city of Sparta. This fault is examined and described in terms of its geometry, segmentation, drainage pattern and post-glacial throw, emphasising how these parameters vary along strike. Qualitative analysis of long profile catchments shows a significant difference in longitudinal convexity between the central and both the south and north parts of the fault system, leading to the conclusion of varying uplift rate along strike. Catchments are sensitive in differential uplift as it is observed by the calculated differences of the steepness index ksn between the outer (ksn

Flooding is one of the most important types of disasters in southern Europe recording many victims and extended damages over the last century. The increased pressure for urban expansion together with the high population density has increased flood risk considerably in the region. Greece is not an exception in this regime, having a very rich flooding record since the ancient times. In this work, an extensive catalogue of flooding phenomena during the last 130 years in Greece has been compiled based on numerous sources. Based on this record the temporal and spatial distribution of flood events and victims was examined. In total, 545 events were identified, causing 686 human casualties and inflicting extensive damage across the country. Results showed seasonality patterns with more events clustering in November. They also showed that urban environments tend to present a higher flood recurrence rates than mountainous and rural areas. An increasing trend in reported flood event numbers during the last decades was discovered, even though the number of human casualties remains relatively stable during the same period. Moreover, spatial patterns were identified highlighting areas and administrational entities with higher flood recurrence rates across the country. © 2012 Springer Science+Business Media B.V.