Although the Tennessee Valley Authority dams have saved Chattanooga millions of dollars in flood damages, they are no guarantee against an extreme flood, as seen recently in California, TVA officials said.
As recently as 1973, torrential rains flooded the Tennessee River and South Chickamauga Creek, closing Lovell Field and causing some $35 million in damages.
As a result, levees were built along South Chickamauga Creek, but they would not be sufficient in the event of an extreme storm, said Tom Barnett, senior manager of TVA's river forecast center.
DID YOU KNOW?
› There are more than 1,200 dams in Tennessee, including 273 rated as “high hazard” because their failure likely would lead to the loss of life.
TVA POWER-PRODUCING DAMS
Fort Patrick Henry
"TVA's system of dams and reservoirs cannot prevent all flooding in the city," he said, noting that it would be politically and economically impossible to expand the levee system to the level needed to protect against almost any storm. "It would be very challenging to acquire the land and the construction costs would be astronomical. The river has become such a focal point there would be a lot of pushback if we started putting levee walls in front of it."
Officials in California scrambled Wednesday to drain more water from a lake behind battered Oroville Dam before new storms hit Northern California and test the quick repairs made after water cascaded down an unpaved spillway and prompted a massive evacuation, the Associated Press reported Wednesday.
Some 200,000 people living downstream of the dam were allowed to return home Tuesday after being ordered to evacuate Sunday.
The swollen lake reached its capacity over the weekend and spilled down an unpaved emergency spillway for nearly 40 hours, leaving it badly eroded. The problem occurred six days after engineers discovered a growing hole in the dam's main concrete spillway.
The incident prompted some in Tennessee to question whether the state's dam and reservoirs are up to par.
There are more than 1,200 dams in Tennessee, including 273 rated as "high hazard" because their failure likely would lead to the loss of life, according to the Commercial Appeal. But nearly half of the state's dams, including 69 rated as high hazard, are exempt from regulation and government inspections because they're classified as farm ponds.
All 10 of the state-regulated dams in Hamilton and Bradley counties are in compliance with the Safe Dams Act, according to TDEC spokesman Eric Ward.
In addition to regular inspections, TVA, which oversees 49 dams and about 100 earthen embankments across its seven-state region, conducts geophysical testing in which technicians drill into the rock and soil of structures to check for problems, according to Commercial Appeal.
"Here in the Chattanooga area last year, we did what they call geo-technical drilling," said TVA spokesman Scott Fiedler. "We were able to drill underneath the [Chickamauga] dam on the upriver side, to see what was down in the earth to make sure everything was safe. Everything is within specifications."
For more on this story, see today's print edition of the Times Free Press.
TVA NON-POWER DAMS
Little Bear Creek
Upper Bear Creek
Source: Tennessee Valley Authority