Towards a better understanding of tropical cyclone flood vulnerability: Flash floods

Flooding is the second leading cause of fatalities due to weather related disasters in the United States. Previous work assessing flood fatalities from 1959-2005 revealed a fifth of all flood related fatalities were a result of tropical systems. A recent study of tropical cyclone (TC) related fatalities unveiled 82% of deaths between 1970 and 99 were a result of drowning; more specifically, 59% of all TC related deaths were due to freshwater flooding. Other studies have also shown a growing trend in flood devastation on the economic and loss of life scale. In an effort to reduce TC flood impacts this study develops a risk index for tropical cyclone-related flooding. Previous flood vulnerability research used stream data and rainfall to assess the likelihood of flooding. Our study differs by using historical TC rainfall data together with TC-related flash flood warnings to develop a climatology of TC flood potential. Results show a far richer spatial structure to the flash flood warnings compared to the smoother TC rainfall climatology, with high flood potential extending far inland in some regions. This index will be incorporated in an overall hurricane disaster risk assessment that will include inland and coastal hazards. The authors anticipate that this vulnerability tool will be a benefit before, during and after a tropical system.