Integrated analysis of societal vulnerability in an extreme precipitation event: A Fort Collins case study
Highlights
► Interactions of extreme rainfall and social vulnerability lead to a flood disaster. ► We combine meteorological and societal data in a spatial analysis of vulnerability. ► The results were validated with an emergency calls database (i.e., 911 calls).
Introduction
Extreme precipitation is one of the factors that contribute to flash floods, but it is the characteristics of the environment, individuals, and society that can turn these natural phenomena into life-threatening disasters (Montz and Gruntfest, 2002). In recent years, extreme weather events have become a leading research topic in many academic fields due to their significant negative impacts on populations and ecosystems as well as recent projections of their altering patterns in a changing climate (IPCC, 2007, CCSP, 2008, Glade et al., 2010, Morss et al., 2011). Extreme precipitation, in particular, presents a major concern because of its wide-spread consequences and secondary hazards, including soil erosion, landslides, and urban flash flooding (Beguería and Vicente-Serrano, 2006).
Characterized by a quick, sudden onset and high intensity over relatively small geographic area, flash floods pose a significant threat to human systems world-wide (Jonkman and Vrijling, 2008). Despite improvements in weather forecasts, early warning systems and flood management infrastructure, extreme precipitation events and resulting flash floods continue to claim human lives and property (White et al., 2001, Jonkman, 2005, Jonkman and Vrijling, 2008, Ntelekos et al., 2006, Ashley and Ashley, 2008). In the United States, for example, on average more than 100 people die and $1 billion of property is destroyed due to floods each year (Chang, 1998). NOAA reports that between 1997 and 2010, on average, 57 people were killed in flash floods annually (NOAA, 2012). In a study of flood-related fatalities that occurred in the U.S. between 1959 and 2005, Ashley and Ashley (2008) report that “the majority of deaths occurred from floods that originated solely from heavy rain in a short amount of time” (p. 812). The reports of flood-related fatalities and the projections of future increases in extreme precipitation events due to anthropogenic climate change (IPCC, 2007, Morss et al., 2011) prompt the need to develop improved disaster preparedness and climate change adaptation strategies that reduce vulnerability to weather extremes. Integrated assessments of societal vulnerability are important steps towards effective preparedness, response actions, and adaptation plans.
Physical characteristics of an extreme precipitation event (i.e., intensity, duration) and of a flash flood event (i.e., suddenness of onset, duration, timing, velocity and depth of water) significantly affect the magnitude and the outcomes of the flood disaster. In urban settings, flood hazard can be amplified by the impact of urbanization and built environment on storm water flow and runoff relationships (Segond et al., 2007). Negative outcomes from extreme precipitation events also largely depend on population density, demographic composition and patterns of human occupancy in urban watersheds (Montz and Gruntfest, 2002). Previous studies showed that the impacts of extreme precipitation events result from complex interactions among meteorological, hydrological, social and behavioral factors (e.g., Grigg et al., 1999, Montz and Gruntfest, 2002, Ahern et al., 2005, Ruin et al., 2007, Ruin et al., 2009, Morss, 2010, Morss et al., 2011), thus indicating the importance of interdisciplinary research and the need for integrated assessments of physical and social indicators of a flooding disaster. In this article we consider integrated assessments broadly, as processes that combine knowledge from multiple disciplines with the goal to aid policy and decision-making (Weyant et al., 1996, Rotmans and Dowlatabadi, 1998). We discuss an integrated assessment of local-level societal vulnerability in an extreme precipitation event that occurred in 1997, in Fort Collins, CO (USA).
Our integrated assessment is framed and informed by previous studies, which suggest several indicators of local vulnerability to events such as flash floods. The ability of human populations to effectively respond to and cope with extreme, life-threatening weather conditions is significantly affected by the demographic and behavioral characteristics of communities and individuals, their access to material resources, and existing adaptive or coping capacity (Montz and Gruntfest, 2002, Plate, 2002, Chakraborty et al., 2005, Ruin et al., 2009, Morss et al., 2011). These factors of social vulnerability vary in space and evolve over time (Gruntfest and Handmer, 2001, Cutter and Finch, 2008). Given the spatially diverse and dynamic nature of both physical and social characteristics, it is important to reassess flood hazard risks, based on new available methods, data, theoretical frameworks, and local contexts (Plate, 2002). To address this need, this study applies theoretical elements of a vulnerability framework, presented in Wilhelmi and Hayden (2010) and in Morss et al. (2011), to assess societal vulnerability in an extreme precipitation event. It does so by using a GIS-based methodology to spatially integrate meteorological and social characteristics associated with vulnerability, based on knowledge about flash flood vulnerability and impacts from the relevant literature. In this study, the local-level analysis of vulnerability is context-specific and takes into account the unique characteristics of the 1997 extreme precipitation and urban flash flood event.
This study contributes to the vulnerability literature in several ways. Past decades of disaster risk research and assessments (Eakin and Luers, 2006, Cutter et al., 2008) have led to multiple approaches to integrating data across disciplinary domains (Cutter et al., 2000, Wilhelmi and Wilhite, 2002, O’Brien et al., 2004, Chakraborty et al., 2005, Patterson et al., 2010). However, no systematic ways have been developed to characterize and quantify risk and vulnerability across hazards, scales and geographic locations and local contexts. Cutter and Finch (2008, p. 2301) note: “methodological difficulties, data quality and access issues and conceptual shortcomings within social vulnerability science limit the development of consistent measures of social vulnerability to natural hazards.” However, there is general agreement in the hazards research community that, regardless of the particular method chosen, integrated assessment of vulnerability is a step towards identifying the “hot spots” within areas of interest and enabling decision-makers to target limited resources for hazard mitigation, disaster response, and climate change adaptation. In addition, linking context-specific vulnerability indicators to either short-term responses (e.g., evacuation) or to long-term disaster risk reduction strategies (e.g., urban planning) has potential to increase usability of the assessments (Chakraborty et al., 2005, Wilhelmi and Hayden, 2010). The case study, discussed in this article, builds on these concepts and presents a local-level, context-specific approach for a simple, operational detection of flood exposure and for reaching out to vulnerable populations during pre-event planning and for emergency response during an extreme precipitation event.
This study also contributes to vulnerability science by specifically focusing on extreme rainfall in an urban area as well as the relationships between vulnerability indicators and the flood outcomes. While a number of previous studies have focused on risk and vulnerability assessments of coastal and river flooding (Sayers et al., 2002, Fekete, 2009, Ciscar et al., 2011), literature assessing vulnerability to extreme rainfall and flash floods has been sparse. There have been a number of studies that focused on physical properties of flash floods (e.g., Beguería and Vicente-Serrano, 2006, Bodini and Cossu, 2010). Impacts from flash floods have been included in vulnerability assessments to flooding hazards (Zahran et al., 2008, Borden and Cutter, 2008). Recently, researchers have started to emphasize importance of social and behavioral aspects, such as risk perception (Botzen et al., 2009) or driving behaviors during flash flooding events (Ruin et al., 2007). Yet few studies have explicitly integrated meteorological data (i.e., spatial and temporal distribution of precipitation) with societal characteristics in assessing vulnerability (Zahran et al., 2008, Ruin et al., 2009). By taking an integrated approach, the study presented here also reflects general research priorities: integrating social science into meteorological research and practice has been a key interdisciplinary direction in the meteorological community (Demuth et al., 2007, NRC, 2010).
During the last two decades, GIS methods and tools, along with remotely sensed environmental information, have been applied in the natural hazards and human–environmental interactions scientific communities to characterize and analyze social vulnerabilities and evaluate risk in a variety of contexts (e.g., Chakraborty et al., 2005, Eakin and Luers, 2006, Cutter and Finch, 2008, Ebert et al., 2009). The availability of GIS technology has enabled vulnerability and risk mapping to become increasingly sophisticated (Eakin and Luers, 2006). Recent advancements in interoperability between meteorological data and GIS can further advance integrated spatial assessments of societal vulnerability to weather-related hazards in a GIS environment (Wilhelmi and Brunskill, 2003, Chapman and Thorne, 2003, Wilhelmi and Betancourt, 2005, Wilhelmi and Brenkert-Smith, 2010). This case study explores this integration through analysis of meteorological data in a GIS, together with spatially explicit characteristics of the local environmental and society.
The case study presented in this article builds on the substantial body of recent and ongoing research focused on developing improved methods for characterizing and quantifying vulnerabilities to natural hazards in general (e.g., Cutter et al., 2000, Turner et al., 2003, Wilhelmi et al., 2004, Chakraborty et al., 2005, Morss et al., 2011) and flash floods, in particular (Ruin et al., 2009). Using the data from the July 1997 Fort Collins, Colorado extreme precipitation event, this study constructs and tests a methodology for integrating radar-derived rainfall with readily available societal information into a GIS-based vulnerability assessment. With the goal of developing specific, targeted emergency response and flash flood preparedness actions, this study aims to assess vulnerability of those urban residents, who may require special assistance during a flash flooding event. Therefore we focus on socio-economic and demographic indicators of vulnerability that represent potential ability of population to respond to and to cope with an extreme precipitation event. These indicators were chosen based on current knowledge of contributors to vulnerability to high-impact weather events, as well as knowledge of the local context. The article also discusses existing challenges and broader implications of integrated assessments of societal vulnerability to high-impact weather events, as well as applications of the methodology and case study findings to other contexts.
Section snippets
The case study
The state of Colorado ranks sixth in the United States in terms of flood-related fatalities (Ashley and Ashley, 2008). Over the past decades, flash floods have caused many deaths and hundreds of millions of dollars of damage throughout the state and along the Front Range of Colorado's Rocky Mountains, in particular. The flash floods are caused primarily by intense rainfall resulting from summer thunderstorms interacting with the topography, land surface and drainage characteristics, and built
Conclusions
In this paper we used a broad definition of an integrated assessment, i.e., combining knowledge from multiple disciplines with the goal of aiding policy and decision-making. The paper focused on the integration of meteorological and societal data using an extreme precipitation event that occurred in Fort Collins, Colorado in July 1997, as a case study. The methodology for integrated assessment of societal vulnerability was based on both the exposure of people and property to flash flood risk
Acknowledgements
The initial analysis for this study was conducted during the SOARS research program. We thank Braxton Edwards, former SOARS protégé, for this help with processing several datasets that were used in this study. We thank the officials in City of Fort Collins for sharing the 1997 flood impact data. We also thankful to Marsha Hilmes-Robinson, City of Fort Collins Floodplain Administrator, three anonymous reviewers, and the editors of this special issue for providing their critiques and valuable
Olga Wilhelmi is a project scientist in the Research Application Laboratory at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. She is also the head of NCAR's Geographic Information Science (GIS) program - an interdisciplinary research effort that integrates atmospheric, environmental and social sciences through spatial analysis and interoperability of georeferenced information. Olga is a graduate of Lomonosov Moscow State University where she majored in physical
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Olga Wilhelmi is a project scientist in the Research Application Laboratory at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. She is also the head of NCAR's Geographic Information Science (GIS) program - an interdisciplinary research effort that integrates atmospheric, environmental and social sciences through spatial analysis and interoperability of georeferenced information. Olga is a graduate of Lomonosov Moscow State University where she majored in physical geography. She completed her Ph.D. in the School of Natural Resources at the University of Nebraska-Lincoln in 1999, and has fifteen years of experience working with GIS in a variety of natural and social science applications, including drought management, heat waves and human health, extreme precipitation events and flash floods. Her current research focuses on research methods for assessing societal risk, vulnerability and adaptive capacity to extreme weather events and climate change.
Rebecca E. Morss is a Scientist III at the National Center for Atmospheric Research in Boulder, Colorado, where she has an appointment in the Mesoscale and Microscale Meteorology Division and directs the Weather Communication and Warning program in the Integrated Science Program. She studies meteorological, socioeconomic, and public policy aspects of weather forecasts, floods, hurricanes, and related topics. Her recent research includes work on the communication and interpretation of hazardous weather risk; use of weather and climate information in decision making; meteorological and oceanographic observing network design; and extreme weather in the context of a changing climate. Among other activities, she recently served on the National Research Council Committee on Progress and Priorities of U.S. Weather Research and Research-to-Operations Activities and on the U.S. National Academies Keck Futures Initiative Steering Committee on Ecosystem Services. From 2009-2012, she served as an elected member of the Council of the American Meteorological Society. She received a B.A. from the University of Chicago and a Ph.D. in atmospheric science from the Massachusetts Institute of Technology.