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Central Texas is still grappling with the aftermath of the floods that devastated the region over the July 4th weekend, leaving over 100 dead and dozens missing.
The historic floods saw the state’s Guadalupe River climb to near-record levels and quickly became one of the country’s deadliest disasters for children in recent decades. For many other states, though, they were also a preview of extreme weather soon to come.
New Mexico. North Carolina. New Jersey. New York. Less than two weeks after the death and devastation in Texas, flooding has hit multiple other states. Monday, July 14, saw particularly intense rains, triggering dangerous flash floods along the East Coast that overwhelmed Virginia roads and New York City’s subways and led New Jersey Gov. Phil Murphy to declare a state of emergency
Flash floods like those that have occurred in recent weeks can be incredibly destructive due to how hard they are to predict. According to the National Oceanic and Atmospheric Administration (NOAA), “[Flash floods] can happen within minutes of the causative rainfall, limiting the time available to warn and protect the public.”
And they seem to be getting even more extreme.
Here’s why flash floods are getting worse, and how you can best stay safe.
Why are flash floods getting worse?
There is not just one reason why flash floods are getting worse and extreme rain events are leading to more high-risk flash flood situations, according to experts.
Jeffrey Schlegelmilch, associate professor of climate at Columbia University, says that climate change has in part escalated “the opportunity for these storms to be holding more water and to have higher rates of rainfall.”
“Rainfall is getting more intense—getting much more intense—downfalls over short periods of time,” in part due to the warmer atmosphere holding more moisture, says Schlegelmich’s colleague, professor of climate with the Columbia Climate School James Smerdon, a professor of climate with the Columbia Climate School,
As a result, instead of infrastructure having to deal with two inches of rain over a longer period of time, it could now face two inches in one hour—potentially leading to subway systems getting flooded, drainage systems getting overwhelmed, or rivers overflowing.
“This speaks to two things: one is the increasing hazard, driven in part by climate change, but then the other is the vulnerability … we have all this stuff built up in areas that are prone to hazards,” Schlegelmilch tells TIME. In New York, he says, “old infrastructure” is renewed in a “piecemeal way,” making it hard to keep up with the escalation of extreme weather events. In Texas, meanwhile, he says “we see some of the waivers to the special flood zones and things like that that sort of have allowed more and more things to be built.”
James Booth, professor of climate change and weather at the City College of New York, adds that he thinks the most important contributor to the escalation in flash flood risk is “increase in exposure because there's more people.”
“For the most part, there's more people in more places across America than there were 50 years ago. So, the increase in exposure [to flash floods]—that's not a tricky physics problem,” Booth says. “I think we can't discount the possibility that there were flood type events back in 1950 that didn't get recorded because they didn't affect anyone.”
While flash floods are on the top of everyone's minds in this moment, Smerdon says, the data “absolutely shows this has been something that's increasing” over the course of “decades.”
How long do flash floods last?
By definition, flash floods occur incredibly fast, and with intense power.
According to the National Weather Service (NWS), flash floods occur within 6 hours, and often within 3 hours, of heavy rainfall. Water can also rise very quickly, as it did in Texas on July 4, when the Guadalupe River rose 26 feet in under an hour.
Where does flash flooding occur most frequently?
Densely populated areas are often at high risk of flash flooding, according to NOAA, because the construction of buildings, infrastructure, and paved roads and parking lots limits the ground’s ability to absorb high intensity rainfall and increases runoff potential.
Areas along rivers, like those along the Guadalupe River that were most affected by the Texas floods, are also incredibly vulnerable.
Schlegelmilch emphasizes that there is also an equity factor to flash-flood risk.
“There has been a lot of research that…formerly racially segregated neighborhoods actually tend to be more exposed to extreme heat and flooding,” Schlegelmich says. He references a study conducted by Redfin in 2021 that found that across 38 metro areas in the nation, more than $107 billion worth of homes at a high risk for flooding were found in redlined communities—25% more than in non-redlined communities.
“Now, more than ever, especially with the pullback in federal attention on this, there needs to be strong local attention that disasters don't affect people evenly, and they don't recover evenly, and some people are going to need more help than others,” he argues.
How to prepare for a flash flood
Schlegelmich says that one of the most important aspects of keeping yourself and others safe prior to flash floods occurring—especially since they happen so fast—is understanding whether you are in a risk zone, and how to respond appropriately based on where you are in the risk zone. He explains that those on hills will have to prepare for what it would mean to become an “island” for a period of time, and those in low ground will need to be able to evacuate safely.
“In virtually any disaster situation, you're either gonna have to stay in one place for a long period of time, you're gonna have to leave very, very quickly,” he says. “Given your situation, what are you gonna do if you have to stay in one place versus if you have to leave?”
He recommends creating a “go-kit” for either scenario, and also assessing where you will get your warning information from—whether that is a NOAA weather radio, or from other warning systems in the area.
He also recommends preparing your property in certain ways, including clearing out storm drains to mitigate damage, and not keeping “critical documents” in flood-prone basements.
What to do if you’re stuck in a flash flood
The main advice for those who encounter flash flooding: seek higher ground as fast as possible.
Schlegelmich also emphasizes relying on local emergency response systems, and understanding “the messages that they're putting out, the evacuation zones, the safest way to get out.”
He also says to beware of water in general at these times, as even minimal amounts can sweep you off your feet: “If you don't know how deep it is, don't go in.”
After the storm passes
“Wait until the water recedes before attempting to hike out,” the U.S. Department of Interior’s Bureau of Land Management advises, noting that flood waters can contain dangerous debris.
Schlegelmich also says that one of the “most important factors in disaster survival” and the aftermath is helping neighbors—whether with getting out prior to flash flooding or cleaning up afterward.
As with before and during a flash flood, he also recommends listening in the aftermath to public officials who know which areas are safe and which are not, as well as which roads are open or closed.
“Some types of assistance may become available through FEMA or through other agencies, and the local emergency management would have information on that,” Schlegelmich says.
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