Flash Flood Forecast and Detection Methods

Abstract

Flash floods occur within minutes or hours of excessive rainfall, a dam or levee failure, or a sudden discharge of water previously held upstream by an ice jam. Flash floods can carry large debris, rip out trees, destroy buildings and bridges, trigger catastrophic mud slides, and scrape out new channels. Rapidly rising floodwaters can attain heights exceeding 10 m (~30 ft). Most flood deaths are associated with flash floods. Most flash floods are caused by slow-moving thunderstorms, thunderstorms repeatedly moving over the same location, or excessive rainfall from hurricanes and other tropical systems. An examination of severe weather fatalities by Wood (1994) indicates that, since 1960, flash floods have killed more people in the United States (around 150 fatalities per year) than any other severe weather phenomena, including tornadoes and lightning (Graziano 1998). The problem is not limited to the United States; excessive rainfall and flash floods can occur anywhere in the world, as long as favorable meteorological and hydrological factors coexist.