By Lee Roberts
NASHVILLE, Tenn. — When the lower Ohio and Mississippi Rivers experienced a flood of record in the spring of 2011, the U.S. Army Corps of Engineers Nashville District supported the flood fight by holding back water at its dams in the Cumberland River Basin reservoir system.
A coordinated water management operation of Barkley and Wolf Creek Dams on the Cumberland River, J. Percy Priest Dam on the Stones River, Center Hill Dam on the Caney Fork River, and Dale Hollow Dam on the Obey River, helped to stem the flow of water.
"A large volume of water was retained in the tributary projects when flows were drastically reduced in late April and early May as a massive flood crest moved down the Ohio and Mississippi Rivers," said Bob Sneed, Nashville District Water Management Section chief.
Looking back at this historical flood event is now the job of the 2011 Post-Flood Performance Assessment team from USACE Headquarters. They have been talking to Nashville District water managers and project personnel while visiting several dams this week to observe how water management operations within the Cumberland River Basin affected flood operations on the Mississippi River.
"This trip is about capturing lessons learned from the 2011 flood. That flood was one of the historic floods in the greater Mississippi River Basin," said Jonathan Davis, USACE deputy chief of Operations and Regulatory, and a co-lead for this flood assessment.
Davis said the assessment looks at the system performance and operational decision making throughout the entire Greater Mississippi River Basin, including the Missouri, the McClellan-Kerr Arkansas River systems, and the events that took place in the Nashville District and the Great Lakes and Ohio River Division.
"Our team is going to select spots in each of these regions, talking to the people who were involved with the flood fighting and getting their perspective on what went well, what they learned from it, and maybe what we can do better next time. And that is really the underlying intent, an internal look at how we can do better," Davis explained.
The assessment will identify system vulnerabilities, evaluate performance of the overall system, evaluate the decision and communication processes, evaluate economic and environmental impacts, identify potential revisions to water control manuals, and recommend operational changes, both within and outside of existing authorities and policies.
Although the assessment is an internal look at USACE actions, an Agency Technical Review Team will participate in the assessment process.
The ATR team consists of economic, water management and geotechnical experts from the Corps, an engineer from Montreal, a professor from University of California Berkeley, and a senior risk adviser from the Netherlands. The team's overall objective is to capture and record observations and recommendations in a Post-Flood Performance Assessment so Corps leadership can use the lessons learned to enhance water management operations during future flood events. At the conclusion of the assessment, the team will present recommendations to a steering committee of senior Corps' leaders and executives.
Lt. Col. James A. DeLapp, Nashville District commander, welcomed the team to the district headquarters July 23. He presented a concise geographic overview of the district, and briefed the headquarters team about the district's operations that supported the flood fight.
"The Cumberland River System in the Nashville District plays a huge part in our ability to manage the overall system on the inland waterways and for that matter the Mississippi (River)," DeLapp said. "The storage at our projects played a significant role in the Corps' ability to manage that properly."
The team also visited Center Hill Dam, Wolf Creek Dam, Old Hickory Dam, Barkley Lock and Dam, and Kentucky Lock and Dam (a Tennessee Valley Authority project) this week during its tour of projects and facilities within the Nashville District. Davis said seeing the projects and talking to the people who were operating them helps the team to better understand special issues and considerations that come into play managing the water.
One big consideration is the ongoing foundation remediation projects at Wolf Creek and Center Hill Dams where concrete barrier walls are being installed to prevent seepage through the karst geology underneath the earthen embankments. The pool levels at these two projects are held at reduced levels during construction for dam safety. But during the flood of 2011, the district assessed the stability of the two projects, and temporary permitted the increase of water being held back to keep from exacerbating downstream flooding.
"It gives us an opportunity now that the event has occurred to replay it, and look at how well we communicated, and see if we could have done better. And again, we're trying to capture that for the future," Davis said. "We've been impressed everywhere we've gone. The professionals at the reservoir projects and in the district office are just the ultimate professionals. Everyone has been extremely helpful in giving us information and being open to us."
Sneed traveled with the group during their tour of the dams. He provided insight of how holding back water impacted the lakes and local communities, and how the district managed the release of water after the lower Ohio and Mississippi Rivers began to recede.
"Our flood control projects, namely Wolf Creek, Dale Hollow, Center Hill and J. Percy Priest, have the capacity to hold back large volumes of water during flood control operations," Sneed said. "During the 2011 Mississippi River and tributaries flood event, we used this flood storage capability to significantly reduce floods in the Cumberland River. By reducing flows out of our tributary projects we were able to preserve storage in Lake Barkley and Kentucky Lake so that storage could be put to work to reduce flows entering the Ohio "River, and ultimately the Mississippi River."
Sneed added that water managers at the Great Lakes and Ohio River Division were responsible overall for the flood control operation and coordinated closely with Nashville District water managers and counterparts at TVA.
Modeling performed after the event indicates that the water stored at Barkley and Kentucky Lakes played the primary role in reducing the flood crest at Cairo, Ill., at the confluence of the Ohio and Mississippi Rivers, by 3.8 feet.
Sneed said Barkley Lake reached a record pool elevation of 372.5 feet, which is about 2.5 feet higher than the previous record mark set in 1984.
During the flood of 2011, the Nashville District's water managers monitored weather, stream and reservoir conditions, managed releases from the Cumberland River Basin reservoir system, and worked closely with the Great Lakes and Ohio River Division, which managed releases from Barkley and Kentucky Dams.
In addition, the Nashville District's Emergency Management Branch coordinated the distribution of 16,000 sandbags to Montgomery County and the city of Clarksville, Tenn. Another 150,000 sandbags were delivered to the Tennessee Emergency Operations Center, and another 544,000 sandbags were issued to counties in Kentucky. The district also provided a sandbag machine to Livingston County, Kentucky and one to the Shawnee Fossil Fuel Plant in Kentucky on the Ohio River at the request of the Tennessee Valley Authority.
The district provided an eight-inch pump to the city of Smithland, Ky., and located 16-inch pipes for pumping operations in Cairo, Ill. A Corps emergency management representative also served as a liaison to the Tennessee Emergency Operations Center for both the Nashville and Memphis Districts during the flood fight.