Fatalities
While the number of fatalities can vary dramatically with weather conditions from year to year, the national 30-year average for flood deaths is 127. That compares with a 30-year average of 73 deaths for lightning, 65 for tornadoes.
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Nearly half of all flash flood fatalities are vehicle-related,
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The majority of victims are males, and
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Flood deaths affect all age groups.
Most flash floods are caused by slow moving thunderstorms, thunderstorms or heavy saturating rains that move repeatedly over the same area. These floods can develop within minutes or hours depending on the intensity and duration of the rain, the topography, soil conditions and ground cover.
Flash floods can roll boulders, tear out trees, destroy buildings and bridges, and scour out new channels. Rapidly rising water can reach heights of 30 feet or more. Furthermore, flash flood-producing rains can also trigger catastrophic mudslides.
Occasionally, floating debris can accumulate at a natural or man-made obstruction and restrict the flow of water. Water held back by the debris dam can cause flooding upstream. Subsequent flash flooding can occur downstream if the obstruction should suddenly release.
