Isabelle Ruin

HYMEX , a 10-year Multidisciplinary Program on the mediterranean water cycle.

The Mediterranean countries are experiencing important challenges related to the water cycle, including water shortages and floods, extreme winds, and ice/snow storms, that impact critically the socioeconomic vitality in the area (causing damage to property, threatening lives, affecting the energy and transportation sectors, etc.). There are gaps in our understanding of the Mediterranean water cycle and its dynamics that include the variability of the Mediterranean Sea water budget and its feedback on the variability of the continental precipitation through air–sea interactions, the impact of precipitation variability on aquifer recharge, river discharge, and soil water content and vegetation characteristics specific to the Mediterranean basin and the mechanisms that control the location and intensity of heavy precipitating systems that often produce floods. The Hydrological Cycle in Mediterranean Experiment (HyMeX) program is a 10-yr concerted experimental effort at the international level that aims to advance the scientific knowledge of the water cycle variability in all compartments (land, sea, and atmosphere) and at various time and spatial scales. It also aims to improve the processes-based models needed for forecasting hydrometeorological extremes and the models of the regional climate system for predicting regional climate variability and evolution. Finally, it aims to assess the social and economic vulnerability to hydrometeorological natural hazards in the Mediterranean and the adaptation capacity of the territories and populations therein to provide support to policy makers to cope with water-related problems under the influence of climate change, by linking scientific outcomes with related policy requirements.

A Unified Flash Flood Database across the United States

Despite flash flooding being one of the most deadly and costly weather-related natural hazards worldwide, individual datasets to characterize them in the United States are hampered by limited documentation and can be difficult to access. This study is the first of its kind to assemble, reprocess, describe, and disseminate a georeferenced U.S. database providing a long-term, detailed characterization of flash flooding in terms of spatiotemporal behavior and specificity of impacts. The database is composed of three primary sources: 1) the entire archive of automated discharge observations from the U.S. Geological Survey that has been reprocessed to describe individual flooding events, 2) flash-flooding reports collected by the National Weather Service from 2006 to the present, and 3) witness reports obtained directly from the public in the Severe Hazards Analysis and Verification Experiment during the summers 2008–10. Each observational data source has limitations; a major asset of the unified flash flood d...

Dynamic vulnerability factors for impact-based flash flood prediction

Social vulnerability explains the sociological and human-dependent circumstances that translate a natural event into a deadly disaster. But, what are the space–time characteristics of vulnerability (i.e., dynamic vulnerability) that influence how people are impacted by a specific natural hazard? This paper performs a critical analysis of previous flood-related human impact and vulnerability studies to better understand and summarize the human-related factors that determine the impacts from flash flood events. The paper is motivated by the hypothesis that the intersection of the spatiotemporal context of the hazard with the distribution of people and their characteristics across space and time reveals different paths of vulnerability and defines the most probable space of an exposed area in terms of deadly impacts. Based on this idea, a conceptual model for assessing vulnerability to flash flooding is developed and presented herein. The most important advance of the current research in comparison with previous efforts in vulnerability assessment is the introduction of the concept of the spatial and temporal variability of vulnerability. This means that the proposed conceptual model does not consider vulnerability as a static synopsis that can be described by a single map, but as an ever-evolving process derived from the interaction of social and physical dynamics. The dynamic perspective of vulnerability is key for the identification of pertinent vulnerability variables to be used for flash flood vulnerability assessment and dynamic mapping, and prediction.

A Situation-Based Analysis of Flash Flood Fatalities in the United States

AbstractThis paper investigates the circumstances of 1,075 fatalities from flash flooding recorded from 1996 to 2014 across the United States. This study provides insights into the situations of the fatality events as determined by the victims’ profile and activity and the spatiotemporal context of the flooding. A reclassification of the individual fatality circumstance (i.e., location and/or activity) is performed to explore statistically the timing, the duration, and location of the flash flood event and the age and gender of the victims. In agreement with other studies, more than 60% of the reported fatalities were related to vehicles involving mainly males. A geospatial analysis indicated these were most common in southern states. Further, 21% of fatalities occurred outdoors, typically in neighborhoods near streams, where the victims were exhibiting high-risk-taking behavior, such as cleaning out drains and even playing in the floodwaters. Human vulnerability varies dynamically on a subdaily basis and...

Urban Area Response to Flash Flood–Triggering Rainfall, Featuring Human Behavioral Factors: The Case of 22 October 2015 in Attica, Greece

AbstractOver the past several decades, flash floods that occurred in Attica, Greece, caused serious property and infrastructure damages, disruptions in economic and social activities, and human fatalities. This paper investigated the link between rainfall and flash flood impact during the catastrophic event that affected Attica on 22 October 2015, while also addressing human risk perception and behavior as a response to flash floods. The methodology included the analysis of the space–time correlation of rainfall with the citizens’ calls to the emergency fire services for help, and the statistical analysis of people’s responses to an online behavioral survey. The results designated critical rainfall thresholds associated with flash flood impact in the four most affected subareas of the Attica region. The impact magnitude was found to be associated with the localized accumulated rainfall. Vulnerability factors, namely, population density, geographical, and environmental features, may have contributed to the...

Toward Probabilistic Prediction of Flash Flood Human Impacts: Toward Probabilistic Prediction of Flash Flood Human Impacts

This article focuses on conceptual and methodological developments allowing the integration of physical and social dynamics leading to model forecasts of circumstance-specific human losses during a flash flood. To reach this objective, a random forest classifier is applied to assess the likelihood of fatality occurrence for a given circumstance as a function of representative indicators. Here, vehicle-related circumstance is chosen as the literature indicates that most fatalities from flash flooding fall in this category. A database of flash flood events, with and without human losses from 2001 to 2011 in the United States, is supplemented with other variables describing the storm event, the spatial distribution of the sensitive characteristics of the exposed population, and built environment at the county level. The catastrophic flash floods of May 2015 in the states of Texas and Oklahoma are used as a case study to map the dynamics of the estimated probabilistic human risk on a daily scale. The results indicate the importance of time- and space-dependent human vulnerability and risk assessment for short-fuse flood events. The need for more systematic human impact data collection is also highlighted to advance impact-based predictive models for flash flood casualties using machine-learning approaches in the future.

Mobility Exposure Scales of Analysis in the Face of Flash Floods

Abstract: As indicated in the Preface, the question of scales is essential to the articulation between water mobility and the mobility of individuals. The hypothesis of this book is that this notion contributes to understanding the emergence of critical situations with a hydrometeorological origin. Thus, we have explored several bibliographical references, which have furnished our reflection on the role of scales in the development process of the hydrometeorological event. First, we worked with articles from Holling and Cash et al., resolutely oriented toward the interactions between environment and society. Then, we sought to deepen the way in which this notion is involved in the analysis of purely social phenomena, more specifically in sociology, by focusing on Grossetti’s article.

18 – Anticipating or Coping: Behaviors in the Face of Flash Floods

Abstract: In the wake of the flash floods that hit the state of Colorado in 2013 and the Cote d’Azur in the autumn of 2015, the newspapers highlighted the “stupidity” or “irrationality” of individuals during such events, concluding that many deaths could have been avoided if the victims had behaved more sensibly. For example, on September 19 2013, the local daily newspaper “Aurora Sentinel” of the third largest city in the state of Colorado (United States) ran the headline “Flood drivers throw doubt on intelligent life in Aurora”. The article then emphasized the idiotic behavior of drivers who, in the midst of a torrential downpour, when the city was mostly flooded, deliberately drove their vehicles through large expanses of water. The author of the article, who had witnessed this behavior, made it clear that he didn’t think the problem lay in the perception or underestimation of the water level on the roads. He described recurring scenes where drivers of small or large vehicles waited their turn to cross flooded areas or areas with major run-off, watching the cars before them sink into the water up to wheel height and get stuck or, even worse, swept away by the current. The most interesting thing about this online article was the responses and comments posted by readers, which revealed some of the reasons for the drivers’ reactions. These reasons were far from irrational. Above all, they show to what extent behavior during an emergency is determined by everyday priorities. Indeed, many eyewitness accounts indicate that the need to get to work or take children to school is very important, with several people noting that schools and companies did not close and even that some employers (including the federal government) expressly told their employees to try to get to work, even though the safety advice was not to drive.