$100M downtown Nashville flood protection plan unveiled

When Nashville's next 1,000-year flood occurs, Mayor Karl Dean wants downtown to be invincible.

Nearly five years after a historic flood caused $2 billion in damage across Davidson County, Dean on Wednesday unveiled the largest flood protection project the city has ever seen — a $100 million plan for downtown that he says will safeguard its buildings and landmarks during a flood of even greater magnitude.

The most visible addition will be a 2,100-foot-long flood wall along the new West Riverfront Park that will cost around $13 million. It includes 1,200 feet of removable flood wall along First Avenue that would extend north from the Seigenthaler Pedestrian Bridge to Fort Nashborough. The removable part would take just eight hours to erect.

The most expensive piece of the plan, though, is a new $65 million storm water pumping station at Riverfront Park that would take rainfall that is being held back by the flood wall and force it back into the Cumberland River. Metro officials say this would be done in a way that does not flood other neighborhoods or the east bank.

"While the cost is significant, it's small compared to the price we would pay if the river swells over its banks again and flows into downtown," Dean said.

In fact, he stressed, the cost of a devastating flood would be greater today than five years ago because of new additions such as Music City Center, Omni Hotel, an expanded Country Music Hall of Fame and Museum and several restaurants in the SoBro neighborhood.

"The risk to all of these places are higher than many people think," Dean said. "I look at this downtown flood protection system as an insurance policy. We're going to pay a premium so we can reduce our risk for catastrophic flooding in the heart of our city."

Construction is expected to begin by the end of the summer and take 30-36 months. The Metro Council last spring approved funding for the project in the Metro Water Services' 2015 capital improvements budget. Dollars will come from municipal revenue bonds that are paid off by fees paid by Metro Water ratepayers. The Dean administration insisted that water rates will not increase as a result.

Nashville-based Barge Waggoner Sumner and Cannon Inc. is the project's lead engineer. Skanska USA will oversee its construction

Each element of the plan is to work in unison, according to Metro Water Director Scott Potter, and the system would only be deployed in anticipation of emergency flooding. Similar systems are used in other U.S. and European cities.

The plans calls for new gate closure structures to close multiple springs, tunnels and sewers that flow into the Cumberland River near downtown. These tunnels — some that go back to the 19th century — absorb rainwater from hundreds of acres near downtown. Blocking them before emergencies would keep the Cumberland from backing up into the system and flooding downtown.

The base of the flood wall would go as deep as 30 feet to prevent water undermining the wall. The removable section is similar to one Gaylord Opryland Resort & Convention Center has built farther up the Cumberland. The permanent flood wall near the new park — site of a future music amphitheater — will look like and function as a walkable promenade that will offer views of the river.

Meanwhile, two diesel-powered generators would allow the new storm water pump to operate even if electricity from Nashville Electric Service goes out.

It's an assortment of new upgrades, and yet it's unclear when the system would be fully used. Potter said there hasn't been a rain episode since the flood in May 2010 that would have prompted its complete implementation.

"We've got a detailed operating plan that will say when the river gets to this level, we'll construct the flood wall," Potter said. "I don't think I'll have the guts, essentially, to wait too long. If it looks like we're going to have an event, we're going to get the wall."

Flooding over the first weekend of May 2010 resulted from nearly 14 inches of rain that fell in Nashville. Some of the event's lasting images were of a submerged downtown that damaged landmarks such as the Schermerhorn Symphony Center, Bridgestone Arena and the Pinnacle at Symphony Place high-rise.

Flood damage, though, was just as bad, if not worse, in suburban neighborhoods such as Bordeaux, Donelson and Bellevue — a point that some immediately raised after Dean unveiled the new flood protection system Wednesday.

"I don't have a problem with securing downtown," said Bo Mitchell, a Bellevue-area Metro councilman and state representative. "But there are 2,497 FEMA-recipient households in the Bellevue area alone that would like some protections, too."

Dean's administration has countered that argument by noting that Metro has already invested $127 million in flood mitigation efforts in other parts of the county. The bulk of those funds went toward a home-buyout program where the city purchased and demolished 267 flood-prone homes. Metro also upgraded the MetroCenter Levee, among other initiatives.

Planning on Nashville's flood preparedness goes back to the summer of 2010. It eventually turned into a 2013 countywide flood plan that identified 22 high-priority locations vulnerable to flooding. Among them is downtown.

Despite the latest undertaking, Metro officials say they haven't forgotten about the east bank, which is to be the subject of a future flood mitigation study. Potter on Tuesday met with officials from the Tennessee Titans — whose LP Field was damaged during the 2010 flood — to tell them that the new flood protection system would not negatively affect the stadium.

The mayor's office has also been in communication with the U.S. Army Corps or Engineers, which according to Dean aides, has signed off on the project.

For Dean, who is term-limited and set to exit the mayor's office in September, the new flood protection system will likely mark his final signature project — five years after he received accolades for leading Nashville during the flood and the cleanup that followed.

He said he doesn't want to see that kind of devastation ever again.

"Even though I'm going to leave office in about six months, this is exactly the type of issue that you do not punt to the next mayor."

Reach Joey Garrison at 615-259-8236 and on Twitter @joeygarrison