The 10 dams operated by the U.S. Army Corps of Engineers in the Cumberland River Basin prevented an estimated $1.8 billion of damages during the region’s late March flood event.
Nashville received 7.01 inches of rainfall March 27 to 28, 2021, the second-highest two-day total since precipitation record keeping began in 1871. The water level on the Cumberland River in Nashville reached 40.55 feet, exceeding flood stage by 0.55 feet.
Natural hydrologic modeling — modeling of the height of the river without flood control projects in place — shows the river would have reached 55.7 feet if the upstream flood control dams did not exist. It would have exceeded the May 2010 event by nearly 4 feet and come within 0.5 feet of the flood of record set in 1927.
The Corps operates four flood control dams upstream of Nashville (Wolf Creek, Dale Hollow, Center Hill, and J. Percy Priest). Since these projects were completed, Nashville has exceeded flood stage of 40 feet only six times (1974, 1975, 1984, 2010, 2019, 2021), averaging a flood every 8.5 years. Before that, with hydrologic records back to 1826, Nashville exceeded flood stage 76 times, averaging a flood about every two years.
Robert Dillingham, hydraulic engineer in the U.S. Army Corps of Engineers Nashville District Water Management Section, said Wolf Creek Dam on the Cumberland River in Jamestown, Ky.; Dale Hollow Dam on the Obey River in Celina, Tenn.; Center Hill Dam on the Caney Fork River in Lancaster, Tenn.; and J. Percy Priest Dam on the Stones River in Nashville, Tenn., stored a combined 1.8 million acre-feet of water during the March high-water event.
“The water was safely stored behind these dams to allow downstream unregulated floodwaters to subside. Once downstream conditions allowed, this stored water was released in a controlled fashion over a period of many weeks,” Dillingham said.
William Terry, Water Management Section chief, said the dam projects in the Cumberland River Basin play a vital role in supporting flood risk management, navigation, hydropower, water supply, water quality and recreation. While all project purposes are important, flood risk management served as a primary driver in Congress authorizing the projects in the Cumberland River Basin, he added.
“Flooding will never be eliminated, but with the flood risk management system in place, the Corps of Engineers and agency partners often reduce the impact and damages caused by flooding,” Terry said. “I’m happy to report that during the March 2021 event that the operation of the dams saved an estimated $1.8 billion of flood damage.”
The Nashville District maintains the Cumberland River Reservoir System with partnerships with the National Weather Service, Tennessee Emergency Management Agency, Kentucky Division of Emergency Management, United States Geological Survey, and Tennessee Valley Authority.
“We work closely together to support operating objectives, especially with mitigating flood risk,” said Lt. Col. Sonny Avichal, Nashville District commander. “I’m especially proud of our water managers and dam operators who work together to balance holding back and releasing water as required to support the Congressionally-authorized purposes at each of the 10 dams in the Cumberland River Basin.”
The Water Management Section schedules reservoir releases based on anticipated river and stream responses to observed rainfall events while preparing for additional forecasted rainfall. The section also designs, operates and maintains databases for hydrological, meteorological, reservoir, water quality and biological data.
The mission of the U.S. Army Corps of Engineers is to deliver vital public and military engineering services, partnering in peace and war to strengthen our nation’s security, energize the economy and reduce risks from disasters.