A U.S. Army Corps of Engineers plan to protect Miami-Dade County from hurricane storm surges over the next 50 years with flood gates across rivers, and a mile-long flood wall along its upscale waterfront, could cost nearly $4.6 billion.
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“If you go back and look at the amount of flooding that occurred during Hurricane Irma and the potential damage and flooding that could occur if something bigger came in like a Hurricane Andrew or Katrina, that's what they're trying to protect us from,” said Miami’s public works and resilience chief Alan Dodd, who is also a retired colonel who ran the Corps’ Jacksonville District.
The agency is developing a similar storm surge plan for Monroe County and other coastal communities. But the scale of the walls and gates — and cost — makes Miami’s plan stand out.
“It's only been used in a few places around the United States,” said Miami-Dade County Resilience Chief Jim Murley. “That's why it will draw, we’re sure, significant attention."
When early conceptual plans were unveiled over the summer, some homeowners worried about having property seized to make room for the structures. Lawyers with the University of Miami’s Environmental Justice Clinic said creating flood protection for some and not others, based on a cost-benefit analysis, could also unfairly exclude some poor neighborhoods.
The study says land will need to be acquired, and estimates the cost at $406 million. However, it’s vague about seizing land and says that would be a last resort.
The county is also reluctant to seize land, Murley said. The Corps and the county share the cost of the project, with the county covering 35 percent.
“There's been no committment by the county to use eminent domain for any purpose on this project, because we don't feel we're at the point where we have sufficient information,” he said.
When it comes to raising or moving structures, the owner needs to be willing, he said.
Environmentalists also say walls and gates could damage seagrass beds, interfere with manatees and other wildlife, and cost more than improving natural barriers like coral reefs and mangroves. The latest 400-page plan, along with 13 appendices, does little to address those concerns, said Miami Waterkeeper Executive Director Rachel Silverstein.
“Almost every individual who showed up to make a public comment about this study was almost begging for green infrastructure,” she said. “Things like restoring coral reefs, building mangroves, dune ecosystems, wetland restoration, and all of those things both provide an environmental benefit, but have also been shown to be really potent storm surge protection features.”
The plan now up for public comment is one of eight alternatives considered. It focuses on seven of Miami-Dade’s most vulnerable areas because protecting the entire county would be too costly. The goal of the project is to reduce storm surge damage and increase resilience, Corps officials say, but not address tidal flooding, like king tides linked to lunar cycles.
In addition to flood gates, pumps and flood walls would be constructed along the Miami River, Little River and Biscayne Canal. Homes and other structures that repeatedly flood in Arch Creek, Little River, Edgewater, Aventura, Cutler Bay, North Beach and South Beach could also be elevated. About 3,800 would be provided with additional flood-proofing.
Countywide, police stations, fire stations, hospitals, and critical structures like pump houses, would be given additional flood protection.
This latest plan moves the flood gate on the Miami River closer to the mouth of the river, said project manager Holly Carpenter. The latest version also eliminates a flood wall in Edgewater and sharply reduces the number of structures to be elevated or flood-proofed.
The plan is also far from final since the $3 million study does not include money for expensive studies modeling flooding or studying hydrology.
“The level of design right now is basically a conceptual level,” Carpenter said, relying on existing information. “We're about 50 percent of the way through a three-year study. And the study will conclude only with the 10 percent level of design.”
Whatever final design is constructed, she said the agency must ensure it doesn't worsen flooding.
“We're not going to prevent storm surge flooding from one side and then induce more moderate flooding on the interior due to the walls,” she said. “We do have the authority to...add additional pumping stations or whatever planning is needed to make sure that doesn't happen.”
The agency is taking public comment for the next 45 days and will hold virtual meetings on June 9 and June 11. More information is available on the Corps’ Back Bay web page.