Nolichucky Dam flow reached nearly twice Niagara Falls during Helene flooding, TDOT says
Flooding from Hurricane Helene caused the Nolichucky Dam near Greeneville, Tennessee, to withstand nearly twice the water flow of the iconic Niagara Falls, the Tennessee Department of Transportation said two days after the historic storm hit East Tennessee.
On the night of Sept. 27, after a day of heavy rainfall in the Great Smoky Mountains, the Nolichucky River was rising at two feet per hour. Around 1.3 million gallons of water were pouring over the dam each second at 11 p.m., according to the Tennessee Valley Authority.
The peak daily water flow of Niagara Falls is around 700,000 gallons per second.
"That gives you a sense of how large of a rainfall event that we're looking at dealing with here," Will Reid, deputy commissioner and chief engineer of TDOT, said during a virtual news conference Sept. 29.
Nolichucky Dam came close to failure
Owner and operator TVA issued a "Condition Red alert" on Sept. 27, warning that a failure of the Nolichucky Dam was imminent. The 94-foot dam, completed in 1913, was invisible under a muddy torrent of water.
The utility posted a video of the dam the morning of Sept. 28, when water was receding by one feet each hour. The record flow of water over Nolichucky occurred late the night before.
Despite the highest water levels the dam had ever experienced, it stood firm and was "stable and secure" by the evening of Sept. 28, TVA said. The river's water level was 9 1/2 feet higher, and the water flow was more than double the previous record set during an Appalachian region flood in 1977.
Hurricane Helene, which was a tropical storm by the time it reached Western North Carolina and East Tennessee on Sept. 27, was more than a "500-year event" for TDOT's infrastructure, Reid said.
Daniel Dassow is a growth and development reporter focused on technology and energy. Phone 423-637-0878. Email daniel.dassow@knoxnews.com.
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