Fatalities Related to Flash Floods Arising from Thunderstorms

Many predict an increase in the frequency and intensity of thunderstorms in the future due to climate change. At present, our knowledge of the risk factors for flash flood deaths in thunderstorms is limited. This report examines the frequency and characteristics of flash flood deaths in the United States from 1994-2005.

We examined mortality data from the National Weather Service Storm Data system. This data originates from local bureau offices. It includes a narrative text summarizing the events. This narrative was abstracted for each flash flood death to identify the place and date/time of the event, age of the victim, gender, activity the victim was participating in, and whether the death was related to work or a motor vehicle. Only deaths arising from direct contact with flooding waters are considered in this report.

Overall, 606 deaths from flash floods were identified in this 12-year period. Fatalities varied by season (higher in spring/summer), time of day (higher in evening), and gender (61% male). 24% of the fatalities were among children and 62% involved a motor vehicle. Drowning was the cause of 94% of the deaths. Differences existed between deaths from driving and non-driving activities. Driving deaths were highest in the evening. Non-driving deaths occurred primarily in the summer, among children, and during daylight hours.

Distinct patterns characterize flash flood deaths. Most involve individuals driving motor vehicles into flooding waters, occur in the evening, and are focused on males. The results suggest that tailored prevention strategies might provide future benefit.