Rapid 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
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, tropical storm, or meltwater from ice or snow flowing over ice sheets or snowfields. 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 b... Wikipedia