Of these damage centers, Chattanooga is at greatest risk. The city sits in a low plain between the eastern and western parts of the Tennessee Valley just above the point where the Tennessee River passes through the Cumberland Mountains.

Before TVA started its flood operations, major storms occurring in the 21,400-square-mile drainage area above Chattanooga would cause the Tennessee River to rise rapidly. When it reached Chattanooga, the swollen river would attempt to carry more water through the narrow mountain passes below the city than the river channel would allow. The excess water that could not flow immediately through the mountains would naturally back up to the city, flooding it on the average of once a year. For this reason, reducing the flood risk at Chattanooga was a major priority in the design of the TVA reservoir system and remains a major operating priority today.

An important point...

The TVA dam and reservoir system prevents millions in flood damages in an average year, but it cannot prevent all flooding.

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 crested at 52.4 feet.

The original flood protection plan for Chattanooga called for the construction of levees to supplement the protection provided by upstream reservoirs. But because the city did not meet the requirements of the Flood Control Act of 1936, the levee system was never constructed.