Photo: @GreggAbbot_TX on X
The overflow of the Guadalupe River left more than 100 people dead and revealed how the combination of torrential rainfall, poorly absorbent soils, and a warmer atmosphere can turn a storm into a tragedy
By Cira D. Apitz
Residents of Kerr County, in the heart of Texas, know the hilly region where they live is prone to flash floods. But no one expected what happened in the early hours of July 4: a sustained and intense downpour that turned the Guadalupe River into a nearly 26-foot wall of water, sweeping away everything in its path and leaving more than 100 people dead.
A Perfect Storm
Flooding from torrential rain is nothing new. But over the past decade, rising ocean temperatures have added more moisture to the atmosphere. As a result, some storms resemble a modern-day Great Flood, becoming increasingly intense and devastating.
Andrew Kruczkiewicz, Senior Staff Associate II at the National Center for Disaster Preparedness (NCDP) at Columbia Climate School, explained in a July 15 interview published in State of the Planet several factors came together to trigger the flooding of the Guadalupe River and the subsequent landslides.
In this case, moisture from the remnants of Tropical Storm Barry interacted with a mesoscale convective vortex, a spinning system that forms when warm, moist air rises rapidly inside large thunderstorms. This interaction led to the formation of new, extremely intense storms packed with rain that moved slowly across the region.
Kruczkiewicz said one of the signs of climate change is that a warmer atmosphere creates tropical systems with more moisture. While flash floods are common in the Texas Hill Country, he emphasized it is worth asking whether climate change is making these events worse. He also pointed to factors such as socioeconomic shifts, land use, and changes in the landscape, which may be contributing to rising risk levels.
Dry Soil Made Things Worse
Another key factor was that the ground was already drier than usual, which reduced its ability to absorb rainwater. As a result, the impact on local communities was even greater.
John Nielsen-Gammon, a climatologist and director of the Southern Regional Climate Center at Texas A&M University, explained in a July 14 article published by both Grist and Yale Climate Connections that the soil in the hill country is thin and rich in limestone, which limits water absorption. Water quickly flowed down hills and valleys, collecting in rivers. That is why the Guadalupe rose so fast.
Extreme Rainfall Is No Longer Rare
Daniel L. Swain, a climate scientist at the University of California, Los Angeles (UCLA), said during his July 7 livestream Weather & Climate Office Hour that the torrential downpours behind the Texas disaster are the type of precipitation increasing fastest in a warming climate.
He explained that the Gulf of Mexico, being a very warm body of water, produces high levels of evaporation that fuel storm systems and even tornadoes farther inland. In this case, that moisture moved north and interacted with remnants of Tropical Storm Barry, which, although no longer a tropical storm, still carried significant circulation and humidity.
Science Has Warned Us
According to a July 9 article by The Texas Tribune, climate scientists agree the July 4 downpours are a clear example of how a warmer atmosphere can intensify weather events and lead to devastating consequences. They warned that disasters like this will become more frequent if people continue burning fossil fuels and heating the planet.
Claudia Benítez-Nelson, a climate scientist at the University of South Carolina, said these events can no longer be treated as isolated incidents. She noted that rising temperatures are making events like the one in Texas increasingly common. “Torrential downpours are happening more frequently in the United States,” she said.
This aligns with a 2021 report from the United Nations’ Intergovernmental Panel on Climate Change (IPCC), which states: “It is an established fact that human-induced greenhouse gas emissions have led to an increased frequency and or intensity of some weather and climate extremes since pre-industrial times, particularly for temperature extremes.”
The report also explains, “at the global scale, the intensification of heavy precipitation will follow the rate of increase in the maximum amount of moisture the atmosphere can hold, which rises by about 7 percent for every 1 degree Celsius of global warming.”
“The connection to climate change has become much clearer over the past five years. These events are no longer rare, and we have seen them occur repeatedly in many parts of the world,” Swain concluded.
