Evaluation of a Social Vulnerability Index for Utility in Tornado Event Mortality Prediction Open Access

Adams, Erica Elaine (2016)

Permanent URL: https://etd.library.emory.edu/concern/etds/0c483k01k?locale=en


Social vulnerability describes a community's resilience to hazards based on its socio-economic and demographic characteristics, in contrast to the physical vulnerability of its natural and built environment. The Centers for Disease Control and Prevention (CDC) released a Social Vulnerability Index (SVI) in 2009 using 14 socio-demographic variables to rank census tracts across the United States. These 14 variables fall into four main themes: socioeconomic status, household composition, minority status and language, and housing and transportation. The intended purpose of the SVI is to aid state and local governments in planning for all stages of disaster management: mitigation, preparedness, response, and recovery. The SVI is undergoing evaluation for its utility in both predicting human outcomes and planning for disaster-specific scenarios. In support of that effort, this study seeks to determine whether areas of high social vulnerability, as characterized by the SVI, experienced higher rates of mortality during the April 2011 Tornado Outbreak in the southeastern United States. Poisson regression was used to model the interaction between tornado presence and the overall SVI on mortality (adjusting for strength of tornadoes) in census tracts of four states affected by the 2011 tornado outbreak. The analysis was repeated for each of the four individual social themes in the SVI. Resulting rate ratios were generally imprecise across all models. Models containing interactions were not were not found to explain additional variance. Overall, these analyses do not support the hypothesis that SVI modifies the association between presence of tornadoes and mortality in the April 2011 tornado outbreak. However, estimated rate ratios exhibited wide confidence intervals, which is likely due to the extreme nature of the case study event and a low number of data points. Future studies should consider lagged health outcomes, recovery times, and mitigation strategy performance as these indicators may be more likely to accurately assess the SVI's utility as a tool for mitigation, planning, and recovery.

Table of Contents

1. Extended Literature Review

1.1 Social Vulnerability in Disaster Management 1

1.2 CDC Social Vulnerability Index 4

1.3 Validation of the SVI 6

1.4 Mortality and Tornadoes 7

1.5 Case Study: April 2011 Tornado Outbreak 8

1.6 Evaluation of the CDC Social Vulnerability Index 11

References 12

2. Manuscript

2.1 Introduction 18

2.2 Data and Methods 20

2.3 Results 24

2.4 Discussion 28

References 33

Appendix 36

List of Tables and Figures


Table 2.1 Daily Mortality by Tornado Magnitude 21

Table 2.2 Social Vulnerability Index Themes and Variables 22

Table 2.3 Poisson Regression Analysis Model Formulations 24

Table 2.4 Mortality Rate Ratios and 95% confidence intervals for presence vs. absence of tornados and model Deviance for Overall SVI Analysis 25

Table 2.5 Mortality Rate Ratios and 95% confidence intervals for presence vs. absence of tornados and model Deviance for SVI by Theme Adjusting for Tornado Strength 27


Figure 1.1 Census variables included in the composite Social Vulnerability Score 5

Figure 2.1 Study Area with Census Tracts displayed by Social Vulnerability With Tornado Tracts Overlay 22

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