Tennessee Valley Authority
Flood Damage Reduction
Flooding was a serious problem in the Tennessee Valley region before TVA dams and reservoirs were built. Because of poor farming practices, floods washed away the topsoil, causing severe erosion and limiting farmers’ ability to grow crops. The potential for flood damage increased as cities and towns were built along rivers and in some cases, lives were lost.
In an average year, the TVA system prevents about $240 million in flood damage in the TVA region and along the Ohio and Mississippi rivers. To date, the operation of this system has prevented over $5.4 billion in flood losses across the TVA region, including about $4.9 billion in damage averted at Chattanooga. The system has also prevented about $470 million in flood losses in the lower Ohio and Mississippi River drainage basins.
Link to the pages below to find out more about flooding in the TVA region and how TVA works to reduce flood damage.
TVA region rainfall
The Tennessee River watershed is a water-rich area, with an average precipitation of 51 inches a year. December through early May is the major flood season in the Tennessee Valley region because runoff—the amount of water that ends up in the river system after it rains—is higher and because storms tend to be larger during this period.
Flood-prone areas
Dams and reservoirs in the eastern portion of the TVA region were planned primarily to reduce flood damage in Chattanooga, but other areas benefit, too. Flood storage below Chattanooga is used to regulate floods below each of the dams on the Tennessee River and on the lower Ohio and Mississippi rivers.
Flood storage
Room available to hold water in TVA reservoirs to prevent flooding varies with the time of year and potential flood threat. On January 1, the system has the capacity to store about 10 million acre-feet of water. That’s a volume equal to one foot of water covering 10 million acres of land.
How TVA reduces flood damage
TVA prepares for the winter flood season by lowering the level of flood-storage reservoirs to make room to hold the runoff produced by winter storms. When a storm hits, TVA holds the water back by reducing releases from the dams in areas where it is raining. When the rain stops and the danger of flooding is over, TVA gradually lets the water out to get ready for the next storm. In the summer, when flood risk is lower, TVA keeps lake levels higher to support recreation.
Reservoir operating guides
TVA uses reservoir operating guides to make decisions about moving water through the Tennessee River system. These guides show each lake’s typical elevation throughout the year. They are aimed at ensuring that there's enough room in the lakes for flood storage while also providing for hydropower generation, navigation, water quality, recreation, and other benefits.
River Forecast Center
TVA’s river forecasters work around the clock routing water through the Tennessee River system in a way that will provide the most public value given changing weather conditions and water needs.
Ohio and Mississippi rivers
Kentucky Lake, the largest flood storage reservoir in the TVA system, provides over 4 million acre-feet of storage during the flood season, which can be used to reduce flood crests along the lower Ohio and Mississippi rivers.
Floodplain management
TVA dams and reservoirs help to “keep floods away from the people,” but they cannot prevent all flooding. For this reason, TVA also tries to “keep the people away from floods” by helping to ensure appropriate building development in naturally flood-prone areas below TVA dams.