FL - Stilt homes, raised roads, maybe a huge wall. Can Miami-Dade stay safe from storm surge?
Hurricane Ian’s devastation on the Southwest Florida coast sent a chill up the spine of anyone in Miami worried about the next big one — and it sharpened the focus of federal planners working to design and build new barriers to avoid a similar outcome for Miami-Dade.
It’s been almost a century since a powerful hurricane drove storm surge up the Miami River, a worst-case scenario for what is now one of the most densely populated and at-risk coastal cities in the nation.
Ever since Hurricane Andrew set the bar in 1992 for how much damage a storm could do in South Florida, Miami-Dade has avoided the direct path of any of the powerful hurricanes that have crisscrossed the peninsula in recent decades.
But Hurricane Ian’s devastation on the Southwest Florida coast sent a chill up the spine of anyone in Miami worried about the next big one — and it sharpened the focus of federal planners working to design and build new barriers to avoid a similar outcome for Miami-Dade.
“That storm is a reminder of the vulnerability that exists in Miami-Dade County and other coastal communities,” Michelle Hamor, chief of the planning and policy branch of the Army Corps of Engineers, said in a recent kickoff meeting to design a multibillion-dollar federal project to address a devastating hurricane threat often downplayed in Florida.
“It was a clear demonstration of the power of a hurricane to move a wall of water ashore,” said Miami-Dade’s Chief Resilience Officer Jim Murley, in a Tuesday meeting about the project. “Storm surge is the reason the U.S. government has studies going on around the country to evaluate options we have for future protection of the people and the property in Miami-Dade County if we were to experience something as severe as a Hurricane Ian.”
The Back Bay Study, as it’s known, is the biggest potential project to confront the challenge of Miami-Dade’s huge storm surge risk, but it’s only one of several ways the county and state are tackling the looming problem.
A $5 billion solution
The Corps is revisiting a study of the best options to protect the county from its biggest risk in a hurricane — storm surge — after residents, politicians, environmentalists and the business community rejected massive storm surge walls that formed the cornerstone of the Corps’ original $5 billion 2021 plan.
The walls, up to 20-feet high in spots, would have stretched for miles along the coast. In one place it would have run along the bottom of Biscayne Bay, and tied into floodgates at the mouth of Miami’s big rivers and canals. The wall options were widely panned as ugly, environmentally destructive and socially divisive, with “winners” on the inside of the wall and “losers” on the outside. But by the Corps’ calculations, they would have saved hundreds of thousands of buildings in Miami-Dade from tens of billions of dollars in potential damage from a storm with surge rivaling Ian.
This time around, the Corps has given into community pressure for something a little greener, with a focus on natural-based solutions.
“We pushed really hard for that, with public input,” Miami-Dade Mayor Daniella Levine Cava said in an interview. “We’re very happy the Army Corps agreed with us to incorporate natural barriers in the plan to prevent the most disastrous parts of storm surge.”
Moffatt & Nichol/The Miami HeraldThis rendering shows a potential hybrid strategy for protecting coastal Miami-Dade from storm surge, tall sea walls combined with an earthen berm and oyster reefs along the coast.
That doesn’t mean there won’t be a wall at all. In a Tuesday presentation to Miami-Dade’s Biscayne Bay board, Hamor said the Corps was considering solutions that combined natural solutions like storm surge walls, as well as elevating and flood-proofing more homes and businesses to potentially shorten the length of wall needed.
“The question is, is there a scenario where a storm surge wall would make sense in our county?” Murley said.
It’s hard to understate how bad it would be if Miami-Dade got a direct hit from a hurricane with a massive surge. The Corps used computer models to estimate the loss from a worst-case scenario storm — think Hurricane Andrew, but probably a bit bigger. If that example storm hit today, the Miami River could see nearly nine feet of storm surge, and around seven feet in the Biscayne Canal.
Then, they added the projected impacts of ongoing sea rise. If that exact same storm were to hit in 2079, with the additional three feet of sea rise Miami could see by then, the numbers get much higher: twelve feet in the Miami River and eleven feet in the Biscayne Canal.
The Miami Herald/A rendering depicting what the Army Corps of Engineers’ proposed 10-foot high flood walls and doors designed to protect downtown Miami from storm-surge flooding might look like at Bayfront Park. The doors would be closed ahead of storms and open otherwise. Curtis + Rogers Design Studio and the Miami DDA
But with the delayed re-start of the Corps study, construction on any of the potential protections — like home elevations, flood-proofing important public buildings like hospitals and fire stations and mangrove replanting — could still be almost a decade away.
“It’s not if, it’s when the next storm hits Miami,” Col Patrick Kinsman, the Corps’ Norfolk district commander, told Miami commissioners last year. “Every year this 200-year storm could happen. We all hope it doesn’t, but eventually, it’s going to.”
In the meantime
But the federal project isn’t the only way South Florida is tackling its monumental storm surge risk. The two main solutions to the risk of the ocean coming ashore are to armor the shoreline and raise buildings — at least the important parts of them — up and out of the water’s way. And buildings in Florida have been moving up for more than a decade.