The Tennessee River has been flowing higher, faster and browner past Knoxville for nearly two weeks as it carries sediment picked up across Western North Carolina and East Tennessee from Hurricane Helene.
Photos from across East Tennessee's most flood-damaged counties show interstate lanes washed away, industrial complexes torn from their foundations and once-green fields turned to brown muck. As rivers collected heavy runoff from the Appalachian mountains , they scalped the earth, carrying soil and debris downstream.
Thanks to historic spilling from upstream dams, the Tennessee River by downtown Knoxville reached a maximum flow of 60,000 cubic feet per second the week after the storm, according to the Tennessee Valley Authority. Sediment is unable to settle to the bottom of the river at that velocity, Darrell Guinn, senior manager of TVA's River Forecast Center, told Knox News.
The most important factor determining the turbidity, or muddiness, of the river is heavy flows through Cherokee Dam into the Holston River and Douglas Dam into the French Broad River. The two rivers converge near Knoxville to form the Tennessee River.
Water flowing through the dams churns sediment and forces the Tennessee River to move quickly. On Oct. 9, Cherokee Dam was sending around 120,000 gallons of water into the Holston every second, and Douglas Dam around 184,000 gallons of water into the French Broad every second, according to TVA.
"We're supposed to shut off spill tomorrow at Douglas, but we'll still be spilling at Cherokee into next week," Guinn said on Oct. 9. "Maybe by the end of next week, we'll start seeing flows get back down."
The middle to end of the week of Oct. 14-18 is a good "preliminary estimate" for when the Tennessee River may return to normal, Guinn said.
The flow will be around 38,000 cubic feet per second by Oct. 11, the federal utility said. A striking photo of the French Broad converging with the Holston showed a completely transformed torrent of mud flowing from North Carolina into Tennessee.
Three flooding rivers pour into Tennessee
The Pigeon and Nolichucky rivers, which threatened dams with historic flows, empty into the French Broad River shortly before it is dammed to form Douglas Lake. TVA deployed a 4,000-foot floating boom across the lake to catch around 1 million cubic yards of hazardous debris.
To move water downstream into the French Broad, Douglas Dam spilled a record 450,000 gallons of water per second through its gates for days after the flood.
Before Hurricane Helene, the Tennessee River in Knoxville was sitting at a water level of between 812 and 813 feet above sea level, according to river water gauge data from the National Oceanic and Atmospheric Administration. Water levels began a slow climb on Sept. 26, as the first rain from the storm's outer bands came.
The Tennessee River reached 814 feet at 11:45 a.m. on Sept. 27 and 815 feet by the end of the day. The river crested in Knoxville at 3 a.m. on Oct. 2 at 816.74 feet and began a sharp decline that evening. The river is still flowing higher than normal at just under 814 feet.
Throughout Hurricane Helene and its aftermath, the Tennessee River did not reach its flood stage of 820 feet. The record stage is 819.3 feet set March 28, 1994. Heavy releases from dams still caused some localized flooding on the river.
TVA warns Vol Navy of heavy Tennessee River flows
Safety risks in the Tennessee River come not from its muddiness, but from debris and fast flows. TVA warned hundreds of boaters in the so-called Vol Navy to exercise caution ahead of the Tennessee-Florida football game in Neyland Stadium on Oct. 12.
"We have been encouraging people to exercise extreme caution on the river due to the higher than normal velocities, or higher than normal flows, as well as the floating debris," Guinn said.
Travel for the game has already been called into question by Hurricane Milton , set to make landfall in Florida as a destructive Category 3 or 4 hurricane overnight Oct. 9-10.
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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This article originally appeared on Knoxville News Sentinel: Tennessee River to stay brown through next week as Helene sediment flows by Knoxville
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