A geographical analysis of flood casualties in the United States
Ashley, Sharon Trotter
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Flood hazards in the U.S. can be observed by both loss of life and property. Every state in the U.S. experiences floods, and consequently, all are vulnerable to their impacts. The purpose of the study is to illustrate flood hazards in the U.S., investigate the correlation between flood magnitude and fatalities, and examine the relationship between flash flood warnings and fatalities. A comprehensive, nationwide database of the conterminous U.S. was compiled for 1959-2005 in order to complete the objectives of the study. This study finds that flash floods are the leading killer among flood types with the majority of the casualties being male and vehicle-related. Spatially, flood casualties are distributed across the U.S. with notable clusters found along the Interstate 95 corridor in the Northeast, throughout the Ohio River Valley, and along the Balcones Escarpment in south-central Texas. Secondly, the study examines the relationship between flood magnitude and flood deaths. A low, but significant, relationship was found between the two variables. This low correlation indicates that other factors, especially social characteristics, may help delineate deadly from non-deadly flood events. Lastly, in examining the relationship between flash flood warnings and flash flood fatalities, it was determined that 40% of all deadly events from 1986-2005 were not warned for in the county of the fatality. A comparison of unwarned events between 1986-1995 and 1996-2005 showed that the percent of non-warned deadly flood events decreased 19% from the first 10 year period to latter 10-year period. A flash flood index map illustrates counties with high actual flash flood deaths relative to the county’s potential for flash flood deaths. Counties with a lower potential (or risk) for flood deaths (based on population density and total number of flash flood warnings issued over the 20 years) displayed disproportionately higher actual deaths relative to their potential.