Feds Consider A Plan To Protect Miami-Dade From Storm Surge: 10-Foot Walls By the Coast

Climate change threatens to dramatically alter the coastal landscape of Miami-Dade in coming decades — one way or another.

It’s not just rising seas and the threat of stronger hurricanes that could do it. The emerging federal plan to protect communities from those climate risks could also remake entire neighborhoods — starting with running high walls, something akin to I-95 sound barriers, down miles of streets now lined with thousands of homes and businesses.

To get the land it needs for the 10- to 13-foot-high walls, the Corps could seize more than 350 properties through eminent domain. The plan also envisions massive moveable storm surge barriers at the mouths of Miami’s rivers and major drainage canals along Biscayne Bay. It would also elevate 10,000 homes and floodproof 7,000 buildings.

All those proposals also come with an equally stunning price tag: An estimated $8 billion, similar to the original cost estimate to restore the entire Everglades (a number that has since easily doubled).

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These new details come from a presentation the Army Corps gave Miami-Dade County in January and the Miami Herald obtained with a public records request — ahead of the formal release of its draft suggestions this spring. A final decision won’t come for more than a year.

The Corps, the federal government’s engineering arm, has been tasked with coming up with solutions to protect 2.8 million people and $311 billion in property value from the more destructive hurricanes and rising seas climate change is expected to bring to the region. The Army Corps plan looks to 2080, when they predict South Florida could see more than three feet of sea rise.

The big question, obviously, is where would these walls go? The initial maps, planners stress, are far from concrete.

“How do we establish the location of the wall and understand the consequences of that option,” said James Murley, the county’s chief resilience officer. “Those are our questions.”

The draft presentation shows five separate lengths of what are labeled as storm surge barriers or SSBs: crossing the Miami River, on the coast of Brickell, along the water by Edgewater and two roughly tracing Biscayne Boulevard in Miami Shores and North Miami. The walls are nearly contiguous, except for a large gap near the Upper East Side.

Each of them appears to be several miles long, but the Corps did not offer specifics on how many miles of walls were proposed. When crossing roads or water, the walls would have gates that swing closed for a storm but stay open the rest of the time.

At 10 to 13 feet high, the walls would be designed to stop storm surge during a hurricane. They would be ineffective against sea level rise, because the porous rock underneath Miami allows water to seep through.

That could be a blessing for residents on the inside of the wall, but not so much for property outside of it.

Susan Layton, the Army Corps Chief of Planning and Policy for the Norfolk District, said the lines on the map are just estimates and will require much more research to figure out precisely where and how high the walls would need to be.

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“Certainly not this part in the study process and not until later in the design would we have the information we need to decide where a flood wall would go,” she said. “We are still gathering that information.”

Before it builds walls, the Army Corps has to consider how they would affect everything from the environment to the real estate market to the lives of the residents nearby.

“When you build such a big structure you’re going to have some impacts on almost everything, but we’ll do our best to minimize those impacts,” Layton said.

In the presentation, the Corps mentions that acquiring the land needed to build the floodwalls and storm surge barriers could involve forcing owners to sell their property, a process known as condemnation or eminent domain. They estimate they would buy out, relocate or purchase a part of 359 properties in Miami-Dade, many of which are condominiums.

At one point, it notes that Miami-Dade County “has yet to determine willingness to pursue acquisition via condemnation, if necessary.”

“We try to avoid the use of eminent domain. If you’re talking about a large structure like a flood wall, sometimes there’s no way to avoid acquisition,” Layton said. ‘It’s never our first choice.”

Like any local government, Miami-Dade has the power to compel property sales as long as it follows the law. Murley said any possible use of eminent domain would have to be “vetted completely,” but did not rule out the possibility.

“As this discussion has proceeded, we’ve said this is an area in our community that would have to be very well understood,” he said.

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A central point of this plan to protect Miami-Dade relies on barriers across the mouths of the Miami River, Little River and Biscayne Canal. The barriers would be designed to remain open most of the time but closed just before a hurricane came through. They protect inland areas from the surge of ocean water that comes with tropical storms.

To make them work, they’d have to connect to floodwalls on either side.

“There are surge barriers throughout the world and it’s something we’re looking at more and more often in the U.S.,” Layton said.

The plan would also involve elevating 10,000 properties and floodproofing another 7,000. Floodproofing includes anything from installing flood barriers at doors to using flooring that can stand to be flooded repeatedly.

Those numbers could decrease, Layton said, as plans solidify. She said details on how exactly they would go about picking which buildings needed to be lifted or renovated and how it would get paid for is something the county would likely be in charge of deciding.

“It’s been done differently throughout the nation, based on local needs and what works best for the community,” she said.

The plan also calls for mangrove replanting on the coast of Cutler Bay. So-called natural solutions like mangroves have been shown to break up the strong waves from hurricanes as well as clean the water and store carbon dioxide.

The report is an update from a draft set of options suggested in June, when the Corps held workshops and asked people to choose which solutions they preferred. This presentation shows the Corps is leaning toward option seven, the most comprehensive and expensive of the bunch.

It also shows ideas the Corps considered but decided not to pursue, including raising the causeways and building barrier islands.

Because this is not yet an official plan from the Army Corps, Miami-Dade has no formal position on the concept, Murley said.

“We think it’s important to get to the point where we have a fully established document. That is forthcoming,” he said.

The Corps plans to release a formalized version of this plan around May, as well as hold a public meeting and accept comments from the public for more than a month.

The final version of the report won’t be done until October 2021, then it’s up to Congress to find the money for the projects it recommends. On an aggressive timeline, that means project design and engineering wouldn’t get started until 2023 and construction wouldn’t begin until 2026.

The Corps is also working on a similar study of the Florida Keys, but instead of giving Monroe County officials a presentation via PowerPoint last month, officials presented it as an online webinar. Monroe County said it did not have a copy of the webinar to provide the Miami Herald in response to a public records request.

The vast majority of the cost — 65 percent — would be borne by the Army Corps. Miami-Dade and its cities could pick up the rest of the tab. Layton said the $8 billion cost estimate is likely to change as the plan gets more detailed.

The presentation also said the measures would save the region $2 billion a year in avoided damages and other benefits.

“These are all recommendations that are continuing to evolve,” Layton said. “When we release that draft report we hope we will receive lots of feedback.”

To send comments about the draft plan to the Army Corps, email Alicia Logalbo at alicia.logalbo@usace.army.mil or call 757-201-7210.

This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the South Florida Sun Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.

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