Flood vulnerability indices and emergency management planning in the Yazoo Basin, Mississippi

Abstract The alluvial plain of the Yazoo Basin lies in part of the Lower Mississippi River Valley in the south-central United States. The Great Flood of 1927 inundated a large part of the Yazoo Basin and was, until Hurricane Katrina struck the Gulf Coast in 2005, the worst natural disaster economically to have occurred in the United States. It would be naive to believe that a major flood could not recur in this area in the future and emergency planning and mitigation are of critical importance. This study does not evaluate the overall risk of flooding, but rather the vulnerability of any location within the Yazoo Basin to flooding should it occur. A method is presented in which indicators are used to categorize the vulnerability to catastrophic flooding by considering physical, social, economic, and environmental components of susceptibility. Ordinal vulnerability indices are derived for each of these components individually and then combined into a single three-level (low-moderate-high) Flood Vulnerability Index (FVI) using a weighted sum of component vulnerabilities. The results of the indexing method were mapped using Geographic Information System (GIS) tools and validated by simulating a series of floods which modeled catastrophic breaks at 28 different locations along the mainline levee system. The inundation patterns generated by the simulations agree with predictions from the physical vulnerability indicator, and permit evaluation of total impact via the FVI. Mitigation and emergency response planning in the Yazoo Basin are aided by considering the different characteristics of flooding in different parts of the basin.