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flash flood
Sign in to saverapid flooding of low-lying areas, often caused by heavy rain associated with a severe thunderstorm, hurricane, tropical storm, or melt water from ice or snow
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Encyclopedic overview
An underpass in Charlottesville, Virginia, United States during normal conditions (upper) and after fifteen minutes of heavy rain (lower) in 2017 A flash flood after a thunderstorm in the Gobi Desert, Mongolia in 2004
A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash floods may also 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 fewer than six hours between rainfall and the onset of flooding.
Excerpted from Wikipedia’s “flash flood” article, available under the CC BY-SA 4.0 licence.