Deadly Floods in Tennessee Continue The U.S. Summer of Extreme Rain

Deadly Floods in Tennessee Continue The U.S. Summer of Extreme Rain
Brian Mitchell, right, looks through the damaged home of his mother-in-law along with family friend Chris Hoover, left, Sunday, Aug. 22, 2021, in Waverly, Tenn. (Photo: Mark Humphrey, AP)

At least 22 people have died and more than 20 are missing in Tennessee after torrential, record-breaking rain pounded the state this weekend, causing massive floods through rural towns that left a wake of destruction. The extreme rainfall — and the state’s recent history of deadly floods — are consistent with what we can expect as the planet gets warmer and storms get even more intense.

More than 43 centimetres of rain fell on Humphreys County, which is in the centre of the state just west of Nashville, in 24 hours on Saturday. The National Weather Service said that that measurement beat the record for one-day rainfall in the state, set in 1982, by more than 8 centimetres. (The data will go to a panel of experts to be vetted before it’s made official.)

“We had an incredible amount of water in the atmosphere,” Krissy Hurley, a meteorologist with the National Weather Service’s local office, told the AP. “Thunderstorms developed and moved across the same area over and over and over.”

The Damage Is Still Being Added Up in Tennessee

Buddy Frazier, the mayor of the city of Waverly, the county seat of Humphreys County, said in a local TV interview that people in his area didn’t expect the level of rain or the intensity of the floods they saw. “It was something like the quickness of a tornado I guess,” he said. “Someone described it as a tidal wave.”

The death toll includes two 7-month-old twins who were washed away in floodwaters as their father struggled to hold on to them and their two older siblings. Other heartbreaking eyewitness reports and incredible photos of brick walls knocked down by water, piles of debris, flattened homes, and submerged buildings portray a region seemingly caught off guard by the severity of the storm and the strength of the floods.

“No one could get out,” Brandi Burns, the property manager of a housing complex was overrun by floods, told the New York Times, describing how she saw someone trapped in the floodwater yellin for help. “It was racing water,” she said. “We could do nothing about it.”

Hurley told the AP that before this weekend, the worst storm on record in Humphreys County was just 23 centimetres of rain. Flash flood warnings for this weekend’s rain, accordingly, only predicted 10 to 15 centimetres of rain.

Tennessee’s Remarkably Bad Run of Rain

This weekend’s rain is the latest in a string of remarkably intense storms and floods in recent years. In late March, torrential downpours killed four people and spurred dozens of rescues over a weekend. That storm brought more than 18 centimetres of rain to the Nashville area over the course of a weekend, the city’s second-highest two-day rainfall on record. The rains helped make this March Nashville’s second-wettest March on record.

In September 2020, storms over middle Tennessee caused 15 centimetres of rain to fall in just 7 hours. The state’s Mill Creek basin was flooded and authorities also had to undertake numerous water rescues. Hurley said that both the March and September storms were one-in-100 year events.

But perhaps the most notorious of extreme flood to hit the state is 1-in-1,000-year rain event in 2010. More than 33 centimetres of rain fell over two days in Nashville, causing floods that killed 26 people, damaged thousands of properties, and caused $US2 ($3) billion in private property damage.

Heavy Rainfall Is Increasing in Tennessee — and Globally

Tennessee has seen a 14% increase in the heaviest downpours across the state since 1950, according to an analysis by Climate Central. Federal data shows that the Southeast as a whole has seen a 27% increase, and every region of the U.S. has seen the heaviest rainfall tick up since 1950.

It’s not just the U.S., though. The flooding comes just two weeks after the latest Intergovernmental Panel on Climate Change report was released, which took stock of just how fundamentally human-caused climate change is altering our global weather patterns. Rain is no exception. The report found heavy downpours are now 30% more common around the world. That owes to a fairly simple relationship that a warmer atmosphere holds more water. There’s even a term for it: the Clausius–Clapeyron equation, which shows that for every 1 degree Celsius of heating, the atmosphere can hold 7% more moisture.

The planet has warmed about that much since pre-industrial times, and the heavy rains certainly show that relationship playing out in the real world. This summer alone, floods have rocked Europe (twice), China, India, and other parts of the U.S.