The dams and reservoirs of the Tennessee Valley were built primarily to protect Chattanooga. But that city is hardly the only flooding hot spot in the Valley.
TVA’s reservoir system protects 15 damage centers—that is to say, areas likely to suffer flood damage if it weren’t for TVA’s intervention.
Of these Chattanooga is at greatest risk because the city sits just above the point where the Tennessee River passes through the Cumberland Mountains.
Before TVA started flood control operations, major storms occurring in the 21,400-square-mile drainage area above Chattanooga would cause the river to rise rapidly. When it reached Chattanooga, the swollen river would attempt to carry more water through the narrow mountain gorge below the city than the river channel would allow. The excess water that could not flow immediately through would back up into the city, flooding it at least once a year.
Did You Know?
TVA’s reservoir system regulates less than 10 percent of the total stream miles in the Tennessee Valley.
In some cases, local communities along unregulated streams can reduce their vulnerability to floods using structures such as dikes, levees, and floodwalls; channel modifications; high-flow diversions; onsite detention; and other traditional flood mitigation methods.
But reducing flood damage in these areas depends primarily on accurate flood risk information, appropriate siting of new development, effective warning systems, emergency preparedness planning, and public education and awareness.
What History Teaches Us
The largest flood in Chattanooga's history occurred in March 1867, before the TVA system was created. The flood crested at 58 feet and completely inundated the city. Since the completion of the reservoir system, the highest Chattanooga flood stage was nearly 37 feet, which occurred in 1973. Without regulation, the flood would have reached 52.4 feet. Read more about this flood.
The original flood protection plan for Chattanooga called for the construction of levees to supplement the protection provided by upstream reservoir, because the city did not meet the requirements of the Flood Control Act of 1936, the levee system was never constructed.