GIS APPLICATIONS IN THE DEVELOPMENT OF NATURAL HAZARD MITIGATION RISK ASSESSMENT: AN EXAMPLE USING TORNADO EVENTS IN ARKANSAS

The Disaster Mitigation Act of 2000 (DMA 2000, Public Law 106-390) was implemented to reinforce the importance of hazard mitigation. Mitigation is sustained action taken to reduce or eliminate the long-term risk to human life and property from natural hazards. This legislation stresses mitigation in order to promote sustainability as a strategy for disaster resistance. In conjunction with new requirements set out by DMA 2000, FEMA (the Federal Emergency Management Agency) established a new set of planning criteria, of which risk assessment is an integral part. The risk assessment must provide an analysis of all natural hazard events that can affect a state or community, including information on previous events and the probability of future events. Cataloging of past events must contain data with regard to damages, severity, duration, location, and date of occurrence associated with each event. Natural hazard analysis must identify on a map the areas affected or most likely to be affected by each event, highlighting the greatest severity. This risk assessment requirement of natural hazard mitigation planning is where we find GIS to be invaluable.

We used GIS and spatial analysis of tornado events in Arkansas to illustrate the hazard risk assessment process, examining tornado touchdowns with regard to distribution, location, magnitude, periodicity of extremes, incidents of injury and/or death, as well as property damage. By using GIS and spatial analysis we can make inferences as to how geology and/or topography affects the probability of natural hazards in a given location. We organized publicly available tornado event data for the period of 1950 to the present into a database that was uploaded to ArcGIS. We tracked the paths of tornados via latitude and longitude coordinates and layered them with digital elevation models in order to analyze them spatially. We then used statistical analysis to determine the probability that a tornado event would affect various areas of Arkansas. The organization of this database and associated spatial analysis provides efficiency for planning strategies based on past events and for predicting future hazard occurrences.