El Niño likely to spur more floods throughout USA this fall

Thomas M. Kostigen | Special for USA TODAY

Show Caption Hide Caption Signs show huge El Niño growing A massive El Niño that can be seen on Japan's Himawari-8 Weather Satellite could mean the beginning of the end to California's historic drought.

Rivers typically flood in springtime as snowmelt from mountains makes its way downhill and combines with rain. The annual ritual is known as the spring thaw. Now, government agencies are warning that this autumn may behave much like spring.

The National Oceanic and Atmospheric Administration (NOAA) says this year’s El Niño is triggering a higher likelihood for above-normal rain, with higher amounts expected come winter. It's already forecasting an above-average flood watch for the Sierra Nevada.

Wildfires could exacerbate the situation. Such blazes accelerate flood risk because scorched soil doesn’t retain as much water as healthy soil, meaning runoffs occur more easily. This year has seen an above-average number of fires burn areas on the West Coast — about 1,000 more fires than usual in California alone — where El Niño rains would have a significant impact.

Plus, this year's El Niño is forecast to be a record-setting one by the National Weather Service. An El Niño is a weather phenomenon marked by warmer Pacific Ocean temperatures that produces severe weather throughout the world. A warmer ocean transfers more water vapor into the air which, when shaken loose by storms, results in heavier and more concentrated precipitation.

Last week’s eastern Kentucky flood along with those that hit Texas in late May and June — the most devastating in the state’s history — may foreshadow what’s to come in certain parts of the country.

There are four flood types:

• Overbank or overland floods: These are the most common types of floods and occur when waterways overflow their banks because of rain or melting snow.

• Flash floods: These are short-lived events of rapidly rising water. They are usually caused by heavy rainfall in a short period of time. Flash floods can occur within a few minutes or a few hours after rainfall.

• Ice jam floods: These floods happen when chunks of ice join together and create natural dams. Behind the dam water builds up and floods into nearby areas. In addition, when the ice jam breaks, a flash flood can occur.

• Coastal flooding: This happens when storm surge pushes excess amounts of water onto shore by the force of winds. The rise in water levels can cause severe flooding, as it did, for example, during Hurricane Sandy. If storm surge coincides with high tide, crests can reach 20 feet or more.

It’s also worth noting another phenomenon that appears each fall: tidal bores. These are surges of waves created by the incoming tide of a river and exacerbated by the equinox. Surfers seek them out as river waves can reach 10 feet or higher. While amazing to watch and perhaps surf, tidal bores can also be dangerous if waves breach riverbanks.

If you live or vacation near any body of water, check flood hazard maps to evaluate the risk of flooding in your area. You should also put together a flood evacuation plan and share it with family members. Practice flood drills if you can.

If you live in a flood zone, ensure your furnace, water heater and all electric panels are off the ground and away from water’s reach. Construct flood barriers and seal and waterproof basement walls and windows.

You may also consider installing backflow valves to prevent water from backing up in your water system during a flood.

Don’t ignore the risk of floods. They can be deadly. Every state sees floods, and areas as far as six miles away from rivers have been affected by floodwaters.

All this means that although it’s unexpected for this time of year, you should get flood smart now.

Thomas M. Kostigen is the founder of TheClimateSurvivalist.com and a New York Times best-selling author and journalist. He is the National Geographic author of "The Extreme Weather Survival Guide: Understand, Prepare, Survive, Recover" and the NG Kids book" Extreme Weather: Surviving Tornadoes, Tsunamis, Hailstorms, Thundersnow, Hurricanes and More!" Follow him @weathersurvival, or email kostigen@theclimatesurvivalist.com.

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