Flash flood

An urban underpass during normal conditions (upper) and after fifteen minutes of heavy rain (lower)
Driving through a flash-flooded road
A flash flood after a thunderstorm in the Gobi, Mongolia

A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, tropical storm, or meltwater from ice or snow flowing over ice sheets or snowfields. Flash floods may occur after the collapse of a natural ice or debris dam, or a human structure such as a man-made dam, as occurred before the Johnstown Flood of 1889. Flash floods are distinguished from regular floods by having a timescale of less than six hours.[1] The water that is temporarily available is often used by plants with rapid germination and short growth cycles and by specially adapted animal life.[citation needed][dubious ]


Flash floods can occur under several types of conditions. Flash flooding occurs when it rains rapidly on saturated soil or dry soil that has poor absorption ability. The runoff collects in gullies and streams and, as they join to form larger volumes, often forms a fast flowing front of water and debris.

Flash floods most often occur in normally dry areas that have recently received precipitation, but they may be seen anywhere downstream from the source of the precipitation, even many miles from the source. In areas on or near volcanoes, flash floods have also occurred after eruptions, when glaciers have been melted by the intense heat. Flash floods are known to occur in the highest mountain ranges of the United States and are also common in the arid plains of the Southwestern United States. Flash flooding can also be caused by extensive rainfall released by hurricanes and other tropical storms, as well as the sudden thawing effect of ice dams.[2][3] Human activities can also cause flash floods to occur. When dams fail, a large quantity of water can be released and destroy everything in its path.[3]

Other Languages
العربية: سيل
aragonés: Flash flood
brezhoneg: Dic'hlann
Deutsch: Sturzflut
Esperanto: Subita inundo
français: Crue soudaine
Gaeilge: Maidhm thuile
Bahasa Indonesia: Banjir bandang
Nederlands: Stortvloed
日本語: 鉄砲水
română: Viitură
Simple English: Flash flood
Basa Sunda: Caah déngdéng
suomi: Äkkitulva
Tiếng Việt: Lũ quét
Winaray: Daralwa