Corps of Engineers Responds to Criticism Following Flood

The U.S. Army Corps of Engineers released a statement today addressing actions taken to try and lessen the impact of recent flooding on the Cumberland River in Middle Tennessee. The Corps serves the same function on the Cumberland River as TVA serves on the Tennessee River. Following the recent costly flooding in Middle Tennessee, the Corps has been the subject of significant criticism, with many people claiming the federal agency failed in its mission to prevent flooding. The Mayor of Nashville says his city suffered at least $1.5 billion in damages.

This is the statement released Thursday by the Corps of Engineers:

May 20, 2010—Nashville, Tenn.—The US Army Corps of Engineers released information today to address subjects related to the Corps’ actions taken during the flood event on May 1-3.

The unprecedented amount of rainfall that fell in the Cumberland River basin overwhelmed the capacity of the dams along the Cumberland River.

“Rainfall from the weekend of May 1-2 set and shattered records throughout the region,” said Lt. Col. Anthony Mitchell, Commander of the Nashville District, US Army Corps of Engineers. “With the amount of rain that fell in uncontrolled parts of the Cumberland River Basin, flooding was inevitable.

“This was a natural disaster, but our dams did their job by holding back much of the rain water, and with controlled releases of water that actually lowered the crest of the river through Nashville.”

Cordell Hull Lake, Old Hickory Lake and Cheatham Lake are all reservoirs created by dams on the Cumberland River. These dams are designed to control the passage of water as it flows through the Cumberland River and are not designed to store large volumes of water. J. Percy Priest Lake, Center Hill Lake, Dale Hollow Lake, and Lake Cumberland (Wolf Creek Dam) are larger reservoirs designed to store water. Outflows from all these storage lakes were reduced and controlled during the flood to reduce the flood crest down river.

Based upon the weather forecast, the Corps took proactive pre-storm action to lower reservoir levels across the system. The initial weather forecast on April 28 predicted 3-5 inches during the weekend. As a result, Corps water management professionals lowered Cordell Hull, Old Hickory, and J. Percy Priest Lakes. Cheatham Lake was lowered a foot. The actual rainfall in some areas exceeded seventeen inches, far more than the predictions.

Since the dams on the Cumberland River have been in place, the worst prior flood occurred in 1975, which crested at 47 feet in downtown Nashville. Much more precipitation fell in uncontrolled areas during this event than in 1975. For instance, the Harpeth River and Mill Creek basins received some of the largest rainfall totals, and their runoff flowed directly into the Cumberland River below Corps dams. The Corps stored as much water as possible, but the total rainfall overwhelmed the system capacity, which was greater than a 1,000-year event.

Old Hickory, Cordell Hull, and J. Percy Priest Lakes all were within a foot of overtopping the facility, which could have led to greater flooding. Due to the time and location of the rainfall, the storage capacity at Dale Hollow Lake and Lake Cumberland were not major factors in reducing flooding downstream. The Corps did slow or stop releases at these two dams during the event to lessen impacts downstream.

Since the Corps of Engineers’ dams were built on the Cumberland River, more than $2.2 billion in flood damages have been prevented. Although navigation and hydropower are authorized purposes for parts of the Cumberland River basin, risk management supersedes all other purposes during a high water event.

“I believe our Water Managers did a great job in a tough situation,” said Mitchell. “They were caught in an extremely dynamic flash flood fight and were making minute-by-minute decisions on the operation of eight dams. They were also exchanging data with the National Weather Service and emergency management agencies, doing media interviews, and answering public inquiries. To determine whether the Corps could have improved it is beginning to do After Action Reviews and Lessons Learned process in cooperation with the National Weather Service and other public agencies. Results of this review will be made public when complete.

“It is not the Corps’ intent to publicly refute criticisms or questions raised, but to merely state the facts,” Mitchell emphasized. “We will continue to clarify or correct information as needed, because we want the public to fully understand how we operate our projects.”

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