Posted on August 2, 2023
The Army Corps of Engineers has been working for years on a $4 billion plan to protect St. Tammany Parish from severe flooding — but even the Corps can’t eliminate flood risk entirely from a parish that was hit with monster storm surge and up to 15-inches of rain during Hurricane Ida.
A revised plan, which the Corps made public on July 14, is the latest in a string of drafts going back to 2021, when the agency first announced its mammoth effort to protect the parish from repeat flooding. In this new version, the Corps proposes to lengthen an 18-mile levee that would run from near Lacombe, down to south Slidell and wrap around the eastern edge of the city, running northwest from U.S. 190 Business toward the Walmart east of I-10.
The big changes in this draft, according to Amy Dixon, the Corps’ project manager for the plan, are that the levee has been extended toward Lacombe on its western side, and that 2,000 fewer structures would be elevated, dropping from 8,500 to 6,500.
These updates strengthen the cost-benefit ratio, which could increase the plan’s chances for funding, experts and local officials said.
In teal is the previously proposed levee and floodwall system. In green is the newer proposed plan, which extends the levee up toward Lacombe to the West.
Still, not everyone in the parish will get equal protection if this version of the plan is put into effect.
“I think a lot of people think that, well, the schools are there and the well is there, and the septic system is there, and the firehouse is there — surely they’re going to be protected,” said St. Tammany Parish Council Chairman Jake Airey, referring to Slidell area neighborhoods on the east side of Military Road. “That’s not necessarily the case.”
Even though the specifics of the project have already been debated for more than two years, the Corps isn’t likely to start construction on any part of it for at least another three to five years. “We don’t know when Congress will authorize the project,” Dixon said.
The Corps will hold two public meetings on the plan, one at 6 p.m. Aug. 15 at the Slidell Municipal Auditorium, and a second on Aug. 16 at 6 p.m. at the Firehouse Event Center in Covington. The public comment period is open until Sept. 6 and can comments can be submitted by email to sttammanyfs@usace.army.mil.
Deciding what to protect
The Corps largely uses cost-benefit tests to decide which neighborhoods get flood protection and which don’t. The Corps estimates future flood damages and weighs that against the costs of the project.
“That makes sense, on the face of it,” said Anna Weber, a senior policy analyst with the Natural Resources Defense Council, an environmental advocacy organization.
But one consequence of using these tests is that the more valuable a property is, the higher the dollar-value estimate of future damages. If a property is worth less, the benefits associated with protecting it would be lower.
“These calculations don’t really take into account the people that are affected by these decisions, but really just the property,” Weber said.
Residents in certain parts of the parish, including the Eden Isles neighborhood feel that they’ve been left out of the plan. They’ve been promised home elevations, but not levee protection.
“The elevation plan that they’re using isn’t really worth the paper it’s written on,” said Thomas Thompson, an Eden Isles resident and a commissioner of the St. Tammany Levee, Drainage, and Conservation District.
Also left out are the more sparsely-populated areas to the east of Slidell — communities like Avery Estates, where the parish is aiming to conduct flood buyouts, the Tammany Mobile Home Park, and any subdivisions to the east of Military Road.
“Out there on the east side of Slidell, you’ve got a low population per square mile”, said Roderick Scott, the board chairman of the Flood Mitigation Industry Association, a private group based out of Mandeville. That means the costs of levee protection per house are higher, and therefore harder for the Corps to justify.
Fewer elevations in the works
Instead, for those outside the levee, the Corps is offering thousands of residents what it calls non-structural flood protection — in most cases, paying for their homes to be elevated or flood-proofed.
These kinds of projects, Scott said, “are the coming tidal wave of mitigation work.” Only a few more levees will be built, he predicts, and instead, agencies like the Corps will prioritize elevations, wind-proofing and flood-proofing. These projects “can be accomplished more quickly than a levee can be built,” he added.
The new version of the Corp’s plan indeed reflects those priorities and proposes to elevate some 6,500 buildings in St. Tammany.
Still, this revision to the plan includes non-structural protection for some 2,000 fewer buildings than the last draft, according to Dixon. Cutting those buildings from the plan contributed to a substantial boost to the benefit-cost ratio — which jumped to 2.4 in this plan, up from 1.8 in the one proposed last year. Improving the benefit-cost ratio might help the plan move forward, Airey said.
Ultimately, the success of the plan will rely on the participation of individual residents. Participation in the elevation program is voluntary, and buildings that aren’t up to code won’t be eligible.
