Climate change, inadequate warning systems & hilly terrain: What led to the deadly floods in Texas

Indian Express

a day ago

Flash floods, which began on July 4, have killed at least 81 people across Texas Hill Country, becoming one of the deadliest deluges in the United States in the past 100 years. Emergency services, volunteers and family members are looking for at least 41 people, including 10 girls, who are still missing.
The disaster took place after heavy rainfall swelled the Guadalupe River to more than 20 feet in a matter of hours in several locations, and it ran downstream.
The Hill Country, the region in Central and South Central Texas, is no stranger to flash floods. It is known as 'flash flood alley' for its propensity for fast and furious flooding when extreme rain falls. For instance, in 1987, a rapidly rising Guadalupe River swept away a school bus carrying children from a church camp, killing 10 of them.
However, the latest flash floods have been far more deadly than the ones seen in recent decades. That is because of two primary reasons, the warming climate and inadequate warning systems. Here is a look at the role of both factors.
It has to do with the geography of the region. Hill country is a semi-arid area where soils do not soak up much water, and let it skid along the surface of the landscape. As a result, whenever there is extreme rainfall, the region's shallow creeks (natural streams of water) rise quickly. These creeks then converge on a river, leading to flash floods.
Another factor that contributes to flash floods is something called the Balcones Escarpment. An escarpment is a steep slope or long cliff that forms because of geological faults or erosion, separating two-level land surfaces.
'When warm air from the Gulf [of Mexico] rushes up the escarpment, it condenses and can dump a lot of moisture. That water flows down the hills quickly, from many different directions, filling streams and rivers below,' Hatim Sharif, professor of civil and environmental engineering at the University of Texas, wrote in The Conversation.
Although it is too early to ascertain whether climate change directly impacted Texas flash floods, scientists believe that soaring temperatures are leading to more extreme events such as torrential rainfall and floods across the world, including Texas Hill Country.
Studies have shown that warmer air can hold more water vapour — for every one degree Celsius rise in average temperature, the atmosphere can hold about 7% more moisture. This makes storms more dangerous as it leads to an increase in precipitation intensity, duration and/or frequency, which ultimately causes severe flooding.
In the case of the latest Texas flash floods, warmer than usual water of the Gulf of Mexico could also have contributed to the extreme rainfall. Higher sea surface temperatures lead to more evaporation and moisture transport to the atmosphere, which ultimately results in an increase in rainfall.
'The tragic events in Texas are exactly what we would expect in our hotter, climate-changed, world. There has been an explosion in extreme weather in recent years, including more devastating flash floods caused by slow-moving, wetter, storms that dump exceptional amounts of rain over small areas across a short time. This frequently overwhelms river catchments leading to severe damage to adjacent infrastructure and loss of life,' Bill McGuire, professor emeritus of geophysical and climate hazards at the University College London, said in a statement.
Survivors in Kerr County, the worst affected area, have alleged that they did not receive any emergency warnings before flash floods began. For instance, the Washington Post's review of wireless emergency data from a public database revealed that the county did not send its first Amber Alert-style (those that are sent when a child is abducted) push until Sunday.
Residents did receive a series of flash flood warnings from the National Weather Service (NWS), part of the National Oceanic and Atmospheric Administration (NOAA). However, as these alerts were sent in the early hours of Friday, residents did not get enough time to evacuate the region.
The delayed warnings have raised questions over the Trump administration's decision to push out staffers of the NWS in April. Some experts have suggested that a shortage of staff could have impacted forecasting the storm. NWS officials have denied such claims.