Publication Date


Document Type


First Advisor

Ashley, Walker S.

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Geography


Tornadoes--Risk assessment--United States; Cities and towns--United States--Growth; Hazardous geographic environments--United States


Weather disaster severity and frequency are a function of both hazard risk as well as the underlying socioeconomic settings exposed to the hazard. In general, previous studies have concentrated on how risk or vulnerability influence disaster potential, but not on the important interaction of these two disaster constituents. This dissertation examines a single hazard---the tornado---and evaluates how this hazard's evolving risk interrelates with the important human vulnerability component of residential built-environment exposure. The research assesses these interactions across the high tornado risk areas of the central and eastern U.S. from 1940 to 2100 using fine-scale demographic data and a Monte Carlo model that simulates tornado events and associated impacts on the underlying exposed landscape. This investigation reveals that as the built-environment grows and spreads outward across the landscape over time, tornado impact severity and frequency also increases. Results indicate that although the Midwest contains the greatest societal exposure and the Central Plains region encompasses the highest tornado risk, the Southeast has the greatest probability of tornado disaster. This finding is attributed to the relatively elevated tornado risk and high-density developed land area that characterizes the Mid-South. Disaster potential within the U.S. is also projected to increase as much as 36 fold from 1940 to 2100 due to escalating built-environment development and its spatial footprint in at-risk regions. Additional study findings suggest that it is not solely the built-environment magnitude that controls tornado disaster potential; rather the geographic structure, shape, and density of the built environment is also important in determining a region's tornado disaster potential. In general, enlarging (i.e., enhancing sprawl) developed land area increases tornado impact severity, while restricting land use into a more concentrated land use pattern lowers the odds of tornado disaster. The final section of the dissertation examines the individual effects tornado risk and societal exposure may have on future tornado disaster potential for high-risk locations in the U.S. An experimental control methodology where either the influence of tornado risk or societal exposure is held constant while the other disaster variable is allowed to change throughout the 21st century is employed. Findings reveal that increasing societal exposure will be the primary driver of future tornado impact magnitude and disaster potential. The combination of swelling tornado risk and societal exposure has the potential to increase expected median annual tornado impacts and disaster potential by as much as 171% given the magnitudes of risk and exposure changes examined. By integrating two of the most important disaster constituents---the hazard and its potential targets---a more thorough understanding of future tornado disaster frequency, magnitude, and uncertainty has been reached. This research supports decision-maker needs and risk-based decision processes that seek to reduce future tornado disaster impacts. By using a quantitative approach that reveals uncertainty associated with projections of risk and vulnerability, this investigation promotes a more thorough understanding of changes in tornado disaster potential by assessing components of tornado risk and exposure. Overall, the study provides a perspective of disaster potential that may be used to address policy through adapting zoning laws, refining state and local building codes, and improving infrastructure.


Advisors: Walker S. Ashley.||Committee members: David Changnon; Andrew Krmenec; Thomas Pingel; James Walker.||Includes bibliographical references.||Includes illustrations.


xv, 168 pages




Northern Illinois University

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