How to Survive a Flash Flood

The oldest climate story isn’t about a wildfire or a hurricane, a heat wave or a drought. It’s about a flood.

“The deluge is terrifying not just for its destructive capacity but also for the way it undoes all that has been accomplished, brings us back to the fathomless chaos of beginning,” The New Yorker’s Avi Steinberg writes of this most primordial human fear, the story of which has been echoed across cultures and religions from the Mesopotamian Epic of Gilgamesh to the Bible’s Old Testament to the Ancient Greek Deucalion Myth to stories told by Native peoples across North America. It might also be humankind’s oldest cautionary tale: When the rain starts and the waters begin to rise, pay attention.

In the United States, floods are the deadliest extreme weather phenomenon after heat waves. In particular, flash floods — which the National Oceanic and Atmospheric Administration distinguishes as flooding that “begins within 6 hours, and often within 3 hours, of ... heavy rainfall” — often take people by surprise, or are dangerously underestimated.

With Hurricane Hilary threatening to dump potentially a year’s worth of rain on parts of the southwestern United States in the span of 72 hours, learning how to react to rising waters ahead of time can be life-saving. This is what you need to know.

Know your flood risk

Unlike learning your personal wildfire risk, which is relatively easy, it can be frustrating to try to figure out the flood risk of your home.

FEMA publishes flood maps (you can search by your address here), but the shading key can be hard to make out and I had difficulty getting the images to load. I had my best luck navigating to this version of the map, clicking on the location I was interested in, then clicking to the second page of the pop-up information, where you will see “Flood Hazard Zones” followed by a letter. The letters B, C, and X designate moderate- to low-risk flood areas (though the risk in these locations is not non-existent!) while high-risk areas are marked with A or V.

An example of where to find your individual flood hazard zone on the FEMA flood map.FEMA

Personally, I preferred the clear information laid out at RiskFactor.com. The website told me my neighborhood’s risk (I live by the river in New York City, so mine is “moderate”) and the number of properties in the area that have a “greater than ... 26% chance of being severely affected by flooding over the next 30 years” (for my neighborhood, 16%!). The website will even estimate the “max depth of flooding” of a specific home or building for this year and in the next 30 years.

If you are in a moderate- to high-risk area on either map, you should take steps to prepare for a flash flood. Even if you score lower, you might want to consider preparing your house because minimal risk doesn’t denote zero risk.

Either way, you should read the below section about “what to do if you’re in a car during a flash flood,” since such a scenario can happen to anyone.

What to do before a flash flood

You don’t have to wait for a flash flood warning to begin to prepare for the worst. But if you’re in a situation where you can anticipate flooding — like much of Southern California, Nevada, and southwestern Arizona can right now — you should prepare ahead of time to run errands so you won’t need to leave the house during the storm. Keep in mind, the best way to stay safe during a flash flood is to not encounter the flood in the first place.

Make sure you have enough food for several days, as well as enough pet food for your animals. Also be sure to pick up any prescriptions or medications you might need. Anticipate any other reasons why you might need to leave your home and try to prevent or limit them ahead of time.

Confirm that the contents of your “go bag” or emergency evacuation kit are up-to-date. Here’s a generic checklist of what should go in it, as well as a version in Spanish.

Check the batteries in your flashlights and charge backup batteries for electronics like cell phones, in case the power goes out.

Clean up your yard if you have time; secure outdoor furniture so it doesn’t get blown around.

Prepare electricity-free entertainment options (now is the time to start brushing up on gin rummy).

Check on neighbors or relatives who might not be aware of the coming storm or have made preparations yet.

I can't believe I have to write this, but absolutely do not order Doordash or Uber Eats or food or products from any other courier service during flash flood conditions. Doing so puts other people in direct danger. Your ramen craving can be satisfied later.

What to do if you’re at home during a flash flood

Never wait out a storm in a basement or an apartment that is below ground level if you live in an area with moderate to high flood risk; move to a higher floor or find a different location to shelter in. Even if your home or basement has been okay in previous rainstorms, major flood events can overwhelm city sewer systems and back up water into areas it hasn’t reached before. As Reza Khanbilvardi, a professor of civil engineering and hydrology at City College of New York, told Gothamist after Hurricane Ida killed dozens in New York, New Jersey, and Connecticut in 2021, “Apartments in cellars and basements can be death traps.” Paved urban areas can be especially dangerous in these conditions.

Follow potential evacuation alerts on your phone or on a radio (yes, they still exist!). Sign up for alerts now if you haven’t already.

Seal your important documents in a gallon-size freezer bag or other waterproof bag if you anticipate needing to evacuate, The New York Times suggests.

Unplug electronics and move any valuables to higher floors or locations if you have time to prepare for an evacuation.

If water enters your home, evacuate immediately with your go bag. Do not wait or try to retrieve any additional items. One of the most common ways people get hurt during flash floods is by waiting too long to evacuate. Use your best judgment — if it feels safer to climb to a higher floor than to try to drive to higher ground, do so, but avoid sheltering in an attic where FEMA warns you could get trapped. “Go on the roof only if necessary,” FEMA writes, and “signal for help.”

Do not attempt to walk or swim through floodwaters. Six inches of moving water is enough to knock an adult off their feet. Electrocution is also the second-biggest cause of death during a flood after drowning; never attempt to turn off a circuit breaker box or touch appliances if you are wet or standing in water.

If you come in contact with floodwaters, be sure to wash that area of your body very well when you reach safety.

What to do if you’re in a car during a flash flood

If at all possible, avoid driving during flash flood conditions. Of course, this isn’t always possible — often people are out when they get caught in a storm. The National Weather Service reports that nearly half of flash-flood fatalities are vehicle-related and the “majority” of victims are male.

First and foremost, never, ever drive through floodwaters or around a roadblock or barrier. “Turn around, don’t drown” is a well-worn NWS slogan for a reason. Just 6 inches of flowing water can move a car and just 12 inches can carry it away — it doesn’t matter how good of a driver you are.

Additionally, even if the water looks shallow, it might not be. “Do not attempt to cross a flooded road even if the car in front of you made it through,” meteorologist Bonnie Schneider writes in her book Extreme Weather.

If your car stalls in water, first responders want you to remember“seatbelt, windows, out.” Do not waste valuable time trying to call 911 and wait for rescue. Unbuckle immediately so you are free to move. Then roll down the windows so that if the car’s electrical system shorts out, you still have a means of escape. (As a backup, buy a “Lifehammer” to punch your way through the window and out of your car. If you do not have a Lifehammer or something similar, the pointy metal ends of a headrest can work in a pinch, The New York Times reports.)

At this point, there is “no right answer,” Joseph Bushra, the medical director with Narberth Ambulance, told WHYY. You need to assess the situation. If it is safe to exit your car and escape to higher ground, do so, but plan your path before getting out of the car and remember, just 6 inches of water can knock an adult over.

If it is not safe to try to make it to higher ground, then you need to get on top of your car. Turn on your hazard lights to make the car visible to first responders. Evacuate children first, starting with the oldest child, and tell them to hang onto whatever they can, The New York Times advises. Once you have evacuated and are on top of your car, then call 911.

What to do if you’re forced into floodwaters

It’s not called a “worst-case scenario” for nothing. So what do you do if you end up in the water during a flash flood?

Your number one priority should be to try to get out of the water as quickly as you can. Climb a tree, a building, a car or truck, or head toward any available higher ground.

If you are forced to swim, move perpendicular to the current. Keep in mind this is a last possible resort: “People need to realize that most people who lose their footing in a flash flood don’t get out,” Julie Munger, the founder of Sierra Rescue International, told The New York Times.

If swimming to safety isn’t possible, the Riverside County Fire Department recommends orienting your body so you’re on your back, with your feet down-current, so you can use them to move debris out of the way. “Most victims in swift water die when they get pinned against obstacles, or get trapped in submerged debris and vegetation,” the department writes. Get out of the water or on top of something as quickly as possible — and hold on tight.