Flash Flood
A flash flood is a rapid onset of flooding caused by intense rainfall, rapid snowmelt, or dam failure, often with little or no warning. Flash floods are particularly dangerous because of their speed and force, occurring over minutes to hours rather than the days typical of river floods.
Real World
In July 2021, the German Ahr Valley flash flood killed over 180 people in under two hours when a slow-moving thunderstorm dropped a month's worth of rain onto steep forested hillsides, overwhelming the narrow river channel with little warning.
Exam Focus
Contrast flash flood characteristics (speed, warning time) with fluvial flood characteristics — comparison commands require you to address both sides explicitly.
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