Flooding disasters due to extreme rainfall reached a record high

CNN
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Extreme weather has hit the United States this year with more flooding than any other year – a deadly, sobering statistic that scientists say paints a picture of the future as the planet warms.

The National Weather Service reported an unprecedented 91 flash flood emergencies this year, more than any year since the worst language was first used in 2003.

All flash flood warnings are a sign of a very dangerous situation, but flash flood disasters are the rarest – accounting for about 1% of flash flood warnings since 2019 – and for good reason.

“It’s the ultimate tool in our toolbox,” said Kate Abshire, a hydrologist and director of the weather service’s National Flash Flood Services. “It is a tool to reinforce the idea that there is an extreme threat to life and property and the potential for catastrophic damage.”

The warnings are just one measure of how chaotic and devastating the floods have been so far this year. It killed Dozens of people transformed entire landscapes and cost the United States billions of dollars.

The most recent flash flood emergency occurred last weekend in Roswell, New Mexico. In the desert city, it rained for about half a year in just 24 hours. Streets turned into raging rivers under the cover of darkness on Saturday evening. Hundreds were caught and rescued, and at least two people were killed.

It was exactly the kind of extreme rainfall that scientists expect as the planet warms.

The heaviest rain events are becoming heavier and more frequent as the world warms due to fossil fuel pollution. A warmer atmosphere is able to absorb more moisture like a sponge and express it in the form of pouring rain.

According to Astrid Caldas, a senior climate scientist at the Union of Concerned Scientists, “we are certainly” already seeing the consequences of climate change, reflected in this year’s catastrophic flash flood events.

“Extreme rainfall events have become much more frequent and are likely to continue to occur more frequently,” Caldas continued.

Development around waterways and in mountainous areas also endangers people and increases the risk of catastrophic, life-threatening flooding, said Caldas, who specializes in community resilience.

“It’s about where we build and how we change the natural properties of the water,” Caldas said. “Water will always take the easiest route it can, and the fact that we have built so much, especially on the banks of rivers… is the reason flooding is increasing in the U.S. too.”

The final number of flash flood emergencies varies greatly from year to year and depends heavily on changing weather conditions and tropical systems impacting the United States.

Tropical systems are initially powered by an enormous amount of moisture, which they often release in the form of heavy rainfall.

That was the case this year. Rainfall from Hurricanes Debby, Francine, Helene and Milton was responsible for about half of all flash flood emergencies this year, according to a CNN review of archived warnings.

Helene dumped never-before-seen amounts of rain of up to 30 inches across western North Carolina, causing catastrophic flood damage that left many locations unrecognizable.

Helene alone was responsible for more than 30 flash flood disasters this year; Last year there were a total of 29 flash flood disasters.

Like all heavy rainfall events, tropical systems will become overloaded in a warming world.

They also receive additional buoyancy from extremely warm waters such as the Gulf of Mexico, which not only help them to rapidly intensify but also release additional moisture into the atmosphere.

The oceans are warming as temperatures rise around the globe. The Gulf of Mexico spent much of the summer and early fall in record temperatures, acting like rocket fuel for tropical systems.

All of the hurricanes that hit the United States this year were fueled by the Gulf.

Increasing weather extremes as a result of climate change also contributed to the emergence of a flood disaster.

The South Fork and Salt fires torched thousands of acres in southern New Mexico in early summer, burning hundreds Homes and businesses destroyed and at least two people killed.

Shortly thereafter, heavy rain battered the burned area, triggering several flash flood disasters. As the ash soil, stripped of its ground cover, could absorb less rain, it turned into a raging river of water and debris, causing even more damage.

This fire was just one of dozens of such disasters this year.

In total, there have been at least 45 major flood-related disasters this year, according to FEMA. And in 2024, two dozen extreme weather disasters worth billions of dollars have already occurred in the U.S., CNN previously reported, a number that is straining FEMA’s disaster relief funding.

Flooding disasters will only increase as the atmosphere and oceans warm, combining to form a powerful cocktail that can create a new normal.

“The past no longer predicts the future,” Caldas warned.

CNN’s Ella Nilsen contributed to this report.