Middle Tennessee dams saved $1.8 billion in March flooding

Jun 15, 2021 at 09:39 pm by WGNS

The 10 dams operated by the Corps of Engineers in the Cumberland River Basin prevented an estimated $1.8 billion of flood damages during the late March flood event in the region.

The Stones River in Rutherford County, which flows into and helps make the body of water known as the J. Percy Priest Lake, was one of the many waterways that is helped each year by dams. 

Nashville received a total of 7.01 inches of rainfall March 27-28, 2021, making it the second highest two-day total since precipitation records were kept in 1871. The water level on the Cumberland River in Music City 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 a stage of 55.7 feet if the upstream flood control dams were not in existence. It would have exceeded the May 2010 event by nearly four feet and came within 0.5 feet of the flood of record set in 1927.

The Corps of Engineers operates four flood control dams upstream of Nashville (Wolf Creek, Dale Hollow, Center Hill, and J. Percy Priest). Since these four projects were all 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. Prior to completion of these four flood control dams, with hydrologic records existing back to 1826, Nashville exceeded flood stage 76 times, averaging a flood about every 2 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, Kentucky; Dale Hollow Dam on the Obey River in Celina, Tennessee; Center Hill Dam on the Caney Fork River in Lancaster, Tennessee; and J. Percy Priest Dam on the Stones River in Nashville, Tennessee; all large storage reservoirs, stored a combined 1.8 million acre-feet of water during the March high-water event.

“This equates to 586 billion gallons of water,” Dillingham explained. “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.”

With storage reservoirs holding back water during the rain event, the Cumberland River’s stream gages in Celina, Carthage and Clarksville in Tennessee were well below May 2010 levels. The gage in Celina reached 28.37 feet, well below the reading of 37.62 feet in 2010. The gage in Clarksville reached 38.39 feet, also well below the reading of 46.10 feet in 2010. The gage in Clarksville reached 47.9 feet, far below the reading of 62.58 feet in 2010.

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 well-established partnerships with the National Weather Service, Tennessee Emergency Management Agency, Kentucky Division of Emergency Management, United States Geological Survey, and Tennessee Valley Authority.

“We enjoy great partnerships with each of these agencies and we work closely together to support operating objectives, especially with mitigating flood risk,” said Lt. Col. Sonny Avichal, U.S. Army Corps of Engineers 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 entire team works hard to create hydrologic, reservoir, hydraulic, consequence, and water quality computer models for real-time water management operations,” Terry added.

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