Flash Floods: What Causes Them and How to Avoid Them

Flash floods are potentially the most dangerous (and definitely the scariest) kinds of floods because they happen quickly and often without warning. They are defined by Floodsmart.gov as “rapid flooding of low-lying areas in less than 6 hours” and are typically caused by intense rainfall.

Flash floods often occur in areas where the soil is very dry (like the deserts of the southwest or drought-stricken California), in urbanized areas (where rain falls on pavement and runs into sewer systems), and in places close to bodies of water (like the huge swaths of land that run adjacent to the Mississippi river). Basically, almost anywhere.


Between 2007 and 2014, almost 27,000 flash flood warnings were issued across the U.S. and in every single state. If you’re interested in the frequency of flash flood warnings by region, check out these cool maps from Gawker.

But whether you live in the Southwest or the Midwest, in the mountains or the desert, on the coast or on the Mighty Miss, forecasters are calling for an El Niño winter and heavy rains for much of the country this year, so the smart money’s on being prepared.

With that in mind, here’s what you should know about flash floods and how to avoid them.

What to do during a flash flood watch

A flash flood watch is issued when the conditions are right for flooding. It doesn’t necessarily mean that a flood will happen, only that it could. Nonetheless, it should be taken seriously.

Remember, flash floods can happen quickly.

  • Listen to your TV or radio for weather updates and emergency instructions.

  • Have a plan for where you will go if you need to reach higher ground. Make sure your route avoids low-lying areas and never walk or drive through flood waters.

  • Make sure your emergency flood kit is stocked.

What to do during a flash flood warning

A flash flood warning is issued when a flash flood is imminent or is already occurring. You should:

  • Move to higher ground immediately or stay on higher ground.

  • Keep your TV or radio on and evacuate if necessary.

If you’re at home:

  • Bring in outdoor furniture and move indoor furniture to a higher floor if possible.

  • Unplug all electrical appliances.

  • Turn off your gas and electricity at the main valve (if instructed) to help prevent fires and explosions.

  • Climb to the highest place you can.

If you’re driving:

  • Move to higher ground immediately and avoid stopping near streams, rivers, or creeks.

  • Never drive through flood water, even if it looks shallow. It may be deeper than it looks and just 2 feet of water can sweep your car away.

Do you need flood insurance?

Because flash floods can happen just about anywhere, assessing the need for flood insurance can be tricky. First, you’ll want to determine if you live in a flood plain. If you do, you’ll definitely want to make sure you have adequate coverage.

And even if you don’t live in one, it’s still important to consider the risks for your area. If flash flood warnings are common near you, it’s probably a good idea to discuss your needs with an expert.

Most homeowners insurance policies don’t cover flood-related damages, but a qualified agent should be able to help you find the coverage you need.