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Fact Sheet: Downtown Flood Protection System

2/25/2015

Flood Wall, Flow Controls, Pump Station Would Protect City's Core During Future Flooding Events

NASHVILLE, Tenn. - Mayor Karl Dean was joined by Metro Water Services Director Scott Potter today to detail a downtown flood protection system that would protect the city during future flooding events.

"I look at this downtown flood protection system as an insurance policy," Mayor Dean said "We're going to pay a premium so we can reduce our risk of catastrophic flooding in the heart of our city. We're making an investment in downtown that will pay for itself with the protection it will provide, the people it will keep safe and the businesses it will keep going if our typically peaceful river rages over its banks."

Metro Water Services has been actively working with local, state and federal agencies on flood mitigation efforts to improve public safety and minimize damage to public and private property since the destructive May, 2010 flood. This system would protect downtown from a flood of even greater magnitude and depth than the one that hit the city in May 2010 and caused $2 billion in damages in Davidson County.

"Like other river cities, Nashville can be protected by a floodwall system," Potter said. "The cost of a protection system is minimal compared to the much larger expense of recovery."

Others in attendance today included Larry Atema, Riverfront Park senior project and development manager; Shannon Lambert, lead engineer at Barge, Waggoner, Sumner & Cannon; and Casey Cooper, project engineer at Metro Water Services.

  • A downtown flood protection system was identified as a flood damage reduction solution for downtown Nashville in the Unified Flood Preparedness Plan, which was released in January, 2013, and the SoBro Master Plan in 2012. One component of the protection system - a flood wall - was announced in August, 2013 in conjunction with the unveiling of the West Riverfront Park Master Plan.
  • Approximately $139 million has been spent on flood recovery and mitigation across Davidson County. Some $127 million of it has been spent outside of the downtown area to improve the MetroCenter Levee, buy and demolish 225 flood-prone properties and develop tools to better respond to flooding and keep the public informed, among other projects.
  • The May 2010 floods resulted in $3.6 billion in lost revenue; 13,000 jobs that were temporarily or permanently lost; and 2,700 businesses that temporarily or permanently closed. Since then, $1.2 billion in building permits have been issued.
  • The downtown flood protection plan is a Metro Water Services project that would include four main components:
    1. A 2,100 foot long flood wall that includes 900 feet of permanent wall located inside West Riverfront Park and 1,200 feet of removable flood wall along First Avenue from the Seigenthaler Pedestrian Bridge to Fort Nashborough. The flood wall will include a below grade cutoff wall to prevent water undermining the wall. The top of the floodwall will be at Elevation 422, which is two feet above the crest of the May 2010 flood. The floodwall within the park will look like a stone wall with a cap for seating.
    2. Construction of gate closure structures to close off the Wilson Springs Sewer and Wilson Springs Storm Tunnel to keep the Cumberland River from backing up into the system and flooding downtown.
    3. Construction of a flow control structure to close off the First Avenue Tunnel to keep the Cumberland River from backing up into the system and flooding downtown.
    4. Construction of a Stormwater Pumping Station at Riverfront Park. The pumping station would take rainfall that is being held back by the floodwall and the closed tunnels and force the water into the Cumberland River to prevent flooding downtown.
  • All components of the flood protection system must be built and operational in order to protect downtown from flooding. Each component is equally important.
  • The project will take another six months to finish design and about three years to construct. Total cost of the project is $100 million that would be spent over some four years and financed over 20 to 30 years using municipal revenue bonds. Funding was approved by the Metro Council in Metro Water Services' 2015 Capital Improvement Budget.
  • Timing in building the protection system coincides with construction of Riverfront Park.
  • The temporary wall can be assembled in eight hours with a 10-person crew. Other municipalities and private industry in the United States have recently begun to recognize the combined aesthetic and flood protection benefits of a removable system, and an increase in widespread application across the country is anticipated. A similar system with removable panels has been installed to protect Nashville's Gaylord Opryland Hotel from flooding.
  • An estimated 100,000 linear miles of levee/floodwall in the United States protect numerous American cities from catastrophic flooding. While each flood protection system is specifically tailored to local needs, most of them include a floodwall and/or levee and a stormwater pumping station. Regional examples include Louisville, Memphis, Paducah and St. Louis.
  • The downtown flood protection system will not make flooding worse in East Nashville or downriver. The water will flow faster downstream rather than being diverted toward East Nashville. The velocity of the water (speed of flow downstream) will increase 4 percent, only increasing the depth 0.005 feet (1/16 of an inch) as predicted by hydrologic and hydraulic computer modeling.
  • The majority of Riverfront Park and the under-construction amphitheater are above the flood protection elevation. The northernmost portion of Riverfront Park, which is below the flood protection level, will have a permanent wall.
  • Metro Government has completed several flood mitigation projects. They include the following:
    • Hazard Mitigation Grant Program (Home Buyout): Directly after the May 2010 flood, FEMA approved six Hazard Mitigation Grant Program applications and awarded funding for the acquisition and demolition of 267 homes. Of those 267 properties, 225 have been acquired and demolished, and 42 have withdrawn from the voluntary program. The total estimated cost of the six home buyout applications was approximately $48 million.
    • MetroCenter Levee: The MetroCenter Levee performed as designed during the May 2010 flood and protected the 1,000-acre MetroCenter commercial and industrial development from flood damage. During the May 2010 event, the Cumberland River water level rose to within a few feet of the top of the levee. The levee performed as designed, but vulnerabilities were recognized and damages that occurred during the flood caused further concern. Additionally, the MetroCenter Pumping Station was not capable of maintaining the lake level due to the extreme volume of runoff without bringing in additional portable pumps. Improvements were made to the levee system to increase its reliability for future flood events, and a new pumping station was constructed. Four new pumps, which are capable of handling a 500-year rainfall event, were installed with a standby generator. Two were installed in the new pump station and two in the old station.
    • Situational Awareness of Flooding Events (SAFE) Program: The May 2010 flood emphasized the need for a thorough assessment of the services provided during flood emergencies by federal and local agencies. Nashville SAFE is a partnership between Metro Water Services, Metro Office of Emergency Management, Metro Planning Department, the U.S. Army Corps of Engineers, the U.S. Geological Survey and the National Weather Service, with the consulting assistance of AMEC Earth & Environmental. The SAFE program allows Metro to monitor actual and forecasted river stages and acquire information that can be used to dispatch resources and respond more efficiently to flood-related emergencies.
    • Nashville Emergency Response Viewing Engine (NERVE): NERVE is a free online tool developed by the GIS Division of the Metro Planning Department to provide information to the public during any natural or man-made disaster, such as last week's winter weather situation. NERVE was created after the May 2010 flood in response to residents who said they wanted more information about disaster response services. As an emergency arises, this site provides real-time information about road closures, evacuation areas, school closings, locations of emergency shelters, food and water distribution centers, and disaster assistance centers. NERVE can also help navigate residents to the closest shelters and other emergency resources by routing them around closed roads and evacuation areas.

Flood Protection System presentation

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Photos credit Metro Photographic Services:

Mayor Karl Dean speaks at Flood Protection Systems press conference
Water Services Director Scott Potter speaks at Flood Protection Systems press conference