What Is a Flash Flood? Why Are They So Dangerous?

Flash floods are sudden, intense floods caused by heavy rainfall in a short amount of time. Unlike slow-rising floods, flash floods can happen within minutes and without much warning—especially in urban areas, near rivers or creeks, or after wildfires when the ground can’t absorb water.

Why they’re so dangerous:

  • They can wash away roads, cars, and buildings.

  • Water can rise rapidly, trapping people in homes or vehicles.

  • Even six inches of moving water can knock a person off their feet.

What causes them?

  • Heavy rain over a short period (especially during storms)

  • Dam or levee failure

  • Overflowing streams or blocked drainage systems

Key takeaway: Flash floods are fast, powerful, and life-threatening. You won’t always have time to prepare once one starts—so have a plan in place before it happens.

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Flash Flood Preparedness: What to Do Before, During, and After

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Wildfire Evacuation: What You Need to Know