Severe Weather Awareness Week: Flash Flooding

Posted on 4/23/2019 12:20:49 PM

2019 Severe Weather Awareness week for Pennsylvania is April 22–26. Plan ahead and stay weather aware for safe spring!

Our severe weather and weather safety topic for today is Flash Flooding and Flash Flood Safety.

Flash Floods signWhat is a flash flood?

A flash flood is a rapid flood. During a flash flood, a stream or creek will rise rapidly and crest generally within a few hours after the start of a heavy rain. Flash floods are dangerous because the waters rise so quickly that they can catch people off guard and trap them in precarious situations. This is why the National Weather Service constantly monitors rainfall using rain gauges and radar estimates, as well as monitoring stream and creek levels using automated river gauges and local spotters. Your National Weather Service will issue Flash Flood Watches and Flash Flood Warnings to help alert you to expected flood dangers.

What causes flash floods?

Flash floods are caused when very heavy rainfall, usually from low-moving thunderstorms, overwhelms the natural or man-made drainage systems. Streams, creeks, and smaller rivers are most vulnerable to flash flooding. Flash flooding occurs in urban areas as well as in rural areas.

Flood Watch vs. Flood Warning

A flood watch means that flooding may occur. Residents should stay alert, closely monitor rivers and streams, and be prepared to move to high ground quickly.

A flood warning means that there is actual flooding. Residents should act at once and move to high ground.

Road Closed signFlood Facts for Driving

  • Six inches of water will reach the bottom of most passenger cars, causing loss of control and possible stalling.
  • A foot of water will float many vehicles.
  • Two feet of rushing water can carry away most vehicles, including sport utility vehicles (SUVs) and pick-ups.
  • Remember: Turn Around, Don’t Drown!

What to Do in a Flash Flood

Flash floods occur within six hours of the beginning of heavy rainfall. Below are some guidelines for keeping safe during a flash flood:

  • Go to high ground immediately.
  • Get out of areas subject to flooding.
  • If instructed to evacuate, do so immediately.
  • Do not attempt to cross a flowing stream on foot or by swimming. Even water only six inches deep, when moving at a high rate of speed, can wash you away.
  • Never drive through flooded areas or standing water. Shallow, swiftly flowing water can wash a car from a roadway.
  • Be especially cautious at night when it’s harder to recognize flood dangers.
  • Do not camp or park your vehicle along streams and washes, particularly during threatening conditions.
  • If your vehicle is trapped in rapidly moving water, then stay inside. If water is rising inside the vehicle, then seek refuge on the roof.


  • Listen to authorities for information and instructions. Return home only when authorities say it is safe.
  • Snakes and other animals may be in your house. Wear heavy gloves and boots during clean-up.
  • Be aware of the risk of electrocution. Do not touch electrical equipment if it is wet or if you are standing in water.
  • Avoid wading in floodwater, which can contain dangerous debris and be contaminated. Underground or downed power lines can also electrically charge the water.

This message is brought to you by the IUP Emergency Management Office.