What typically triggers the formation of a flash flood?

Rapid heavy rainfall in a short period is the primary trigger for the formation of a flash flood. When intense rainfall occurs over a short duration, it can overwhelm the natural drainage systems and cause water to accumulate quickly in low-lying areas. This sudden influx of water can lead to swift changes in water levels, resulting in dangerous flood conditions within moments.

While slow and steady rain can contribute to flooding, it typically leads to what is known as riverine flooding rather than flash floods, which are characterized by their rapid onset. Snowmelt can also lead to flooding, but it generally does so over a more extended period as temperatures rise gradually. High tide occurrences can influence coastal areas but are not directly responsible for flash floods in inland areas. The immediacy of heavy rainfall is what distinguishes flash floods as particularly dangerous and unexpected.