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Can Key Biscayne fend off worsening hurricane flooding?

Three cars drive through a flooded street
Tony Winton
Heavy rainfall caused flooded streets in Key Biscayne, June 4, 2022. The rainfall event is the kind of scenario officials are trying to plan for in funding a pressurized storm water system. Nearly 8 inches of rain fell, with an intense burst of 1.8 inches per hour. Climate models say rainfall is predicted to increase in the future.

Key Biscayne, home to one of Florida’s oldest lighthouses that for more than a century guided mariners through rough seas, is getting a modern update to protect itself from worsening hurricane flooding fueled by climate change.

In meetings last month, the U.S. Army Corps of Engineers launched plans to fend off hurricane storm surge across the low-lying island.

“We're looking at water coming in from all different directions,” said Chris McNees, the Army Corps’ project manager. “We'll be doing modeling to not only evaluate the storm surge from the beach side, but we'll also be doing modeling from the back bay side to evaluate what are the damages that occur from [a hypothetical] storm.”

READ MORE: Army Corps agrees to redo billion-dollar plan to fortify Miami-Dade against storm surge

The island, just four miles long and two miles wide, was originally included in the Corps’ larger bay plan to protect areas all around Biscayne Bay. That planning started after the Corps’ extended a look at vulnerable coastlines in the North Atlantic in 2012 after Hurricane Sandy to include another 65,000 miles along the South Atlantic. As work progressed around Biscayne Bay, and including a controversial proposal for a mile-long flood wall, McNees said it became clear that Key Biscayne needed its own plan.

“There's definitely going to be some overlap, but we also see how there could be some individuality,” he said.

At the January meetings, the Corps, Village and Miami-Dade officials asked for public input that will be used to develop a tentative plan. McNees said a list of proposed solutions, which could include flood walls, concrete groins or elevating structures, will be presented to local officials later this month. Based on that meeting, Corps engineers will then begin developing the tentative plan over the next year or more. Miami-Dade and the Corps are splitting the cost of the $1 million study.

Taking a cue from criticism over the mainland study, McNees said this time around Corps officials are listening carefully to local concerns.

“Right now we're just in total brainstorming,” he said. “We'll bring that brainstorming back to Miami-Dade County so that we can continue to kick the tires and see what everybody likes and doesn't like.”

“We're looking at water coming in from all different directions."
Chris McNees, the Army Corps’ project manager

The larger Back Bay study, that focused on seven of the most vulnerable areas along the mainland, initially drew widespread opposition when the Corps released a plan that included mostly concrete barriers, like towering flood gates across the Miami and Little Rivers and a view-blocking wall along Brickell Avenue. Environmental groups pushed to have more mangroves and other natural defenses to help protect the ailing bay while developers opposed walling off views.

Miami-Dade, which shares the cost of work that could amount to nearly $5 billion, instead asked to offer its own version. A new plan is now being hammered out that includes restoring storm-buffering wetlands and living shorelines. Corps officials are hoping to get authorization for parts of the plan as early as this year, although the entire project won’t likely be approved until 2028.

Rebuilt with luxury homes

Once a haven for retirees flocking to newly built squat concrete houses built by the Mackle Bros, the island has been rebuilt with luxury homes and high-rises sandwiched between Crandon Park to the north and Bill Baggs State Park — home to the lighthouse — to the south. At least half those original homes have been replaced with newer, higher homes.

But according to the First Street Foundation’s Risk Factor flood calculator, the Key’s bayside homes face the worst threat from flooding, with nearly all facing a 26% chance of flooding in the next 30 years. Nearly all 31 miles of the island's roads also face a severe risk of flooding.

To fend off future storm surge, McNees said features could include similar proposals being considered for the larger Back Bay plan, but on a smaller scale. That could mean elevating structures, as well as hardening shorelines. Beach renourishment is also in the mix.

The island was also originally part of an update to extend hauling sand to eroded beaches on barrier islands including Surfside and Sunny Isles Beach. But along with the Back Bay study, that work also showed Key Biscayne needed a better network of barriers.

“We realized that while our solutions on the ocean side prevented damages to the Key, the storm surge went around the island,” he said. “So all the damages that we had prevented, and all those benefits that we had recognized from an ocean solution, they were lost from a back bay flooding perspective.”

Over the coming months, Corps engineers will begin modeling flooding impacts from potential storms to identify risky areas, then plug in barriers or protective measures. Since solutions have to justify costs, they’ll also look at financial feasibility. Construction and purchasing land are usually the costliest factors, he said.

A full plan could take three or more years to complete, but McNees said Corps officials will likely return for six-month update following this month’s meeting.

“We want to be sure that we get it right,” he said. “Not only for policy and legally, but we also want to get it right in the eyes of the public.”

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Jenny Staletovich is WLRN's Environment Editor. She has been a journalist working in Florida for nearly 20 years. Contact Jenny at jstaletovich@wlrnnews.org
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