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If Hurricane Ian had struck Southeast Florida, here’s how bad it would have been

Satellite composite image of Hurricane Ian as it emerges from Cuba on its way to Florida at 1 p.m. on Sept. 27
National Hurricane Center
Satellite composite image of Hurricane Ian as it emerges from Cuba on its way to Florida at 1 p.m. on Sept. 27

As federal agencies and local governments reassess flood zones and incorporate new technology, data on sea-level rise and the fact that the concrete jungle doesn’t absorb as much water as the natural environment, they’ve concluded that vast swaths of South Florida — particularly inland areas — are vulnerable to crippling storm surge and flooding from rain.

The nation watched aghast as Hurricane Ian pummeled the west coast of Florida, sending a storm surge of 12 feet into some areas, and dropping 15 to 19 inches of rain on coastal spots such as North Port and even inland to the outskirts of Orlando.

The surge planted yachts atop cars and took out homes, while the flooded Myakka River north of Fort Myers made Interstate 75 impassable. Further inland, flooding inundated apartment complexes and homes across the middle of the state.

What would’ve happened if a similar Category 4 storm struck South Florida, and is your home safe? As the federal agencies and local governments reassess flood zones and incorporate new technology, data on sea-level rise and the fact that the concrete jungle doesn’t absorb as much water as the natural environment, they’ve concluded that vast swaths of South Florida — particularly inland areas — are vulnerable to crippling storm surge and flooding from rain.

Here’s a look at the risks faced by southeast Florida.

Storm surge

Storm surge occurs when the convection of a hurricane pushes water onto land. The Gulf of Mexico, including the west coast of Florida, the Panhandle and all the way to Texas, is much more susceptible to storm surge than the East Coast, said Kait Parker, a meteorologist with IBM’s The Weather Company, which owns the Weather Channel digital properties.

A National Hurricane Center map indicates the storm surge potential for a Category 4 hurricane in various parts of South Florida. Blue indicates 3 feet of surge, yellow indicates up to 6 feet of surge, orange greater than 6 feet, and red greater than 9 feet.
(National Hurricane Center)
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The South Florida Sun Sentinel
A National Hurricane Center map indicates the storm surge potential for a Category 4 hurricane in various parts of South Florida. Blue indicates 3 feet of surge, yellow indicates up to 6 feet of surge, orange greater than 6 feet, and red greater than 9 feet.

That’s due to the topography of the Gulf. “It’s a very gradual incline and it’s shallow … so as that wind is continually pushing over water, it starts to move it, it starts to shove it, it starts to build up,” she said. With the gradual incline, the water builds up. The only place to escape is inland.

On the East Coast, there’s a drop-off, she said. “You have the continental shelf that goes up the East Coast.”

When a hurricane pushes water against the Atlantic shoreline, “water can circulate back down and you don’t have as much that ends up over land,” she said.

“That said, you absolutely can have life-threatening storm surge anywhere near the coast of Florida, period. You are absolutely not safe from storm surge if you live on the East Coast. It’s just different.”

When looking at east coast storm surge for a Category 4 hurricane, The National Hurricane Storm Surge Risk Map indicates that Broward County fares worse than Palm Beach County, and that the southern third of Broward County is particularly vulnerable to storm surge penetration.

Palm Beach County has higher elevation and fewer waterways west of the Intracoastal Waterway. An exception is the area around Jupiter inlet, where some neighborhoods could suffer surge greater than 6 feet above ground level.

In general, the highly valuable properties along the Atlantic Ocean and Intracoastal Waterway would be inundated by up to 3 feet of water, and in some cases close to 6 feet of surge.

In Broward County, things look soggier. Intricate canal systems from Deerfield Beach down to Hallandale Beach, toward Miami-Dade, make for a mess.

“Anything south of Atlantic Boulevard, going all the way to Hallandale, and east of I-95 are areas that are lower,” said Carlos Adorisio, Broward County’s engineering unit supervisor in the Resilient Environment Department. “Within that area there is the coastal ridge, which is a bit higher, but most areas are lower.”

He said fingers of lower elevation follow from north of the New River west to Davie. “If there’s a big hurricane, storm surge will reach those areas,” he said. “If we set back the clock 150 years, those areas are probably the banks of the natural river that used to be there.”

The National Hurricane Center’s surge map for a Category 4 storm echoes Adorisio’s take. On it, areas of inland penetration follow waterways.

A National Hurricane Center map indicates storm surge if a Category 4 hurricane struck South Florida. Blue indicates 3 feet of surge, yellow indicates up to 6 feet of surge. A Category 4 storm would push surge up through low-lying areas along the Cypress Creek Canal, the Middle River and the New River, reaching as far west as Florida's Turnpike.
(National Hurricane Center)
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The South Florida Sun Sentinel
A National Hurricane Center map indicates storm surge if a Category 4 hurricane struck South Florida. Blue indicates 3 feet of surge, yellow indicates up to 6 feet of surge. A Category 4 storm would push surge up through low-lying areas along the Cypress Creek Canal, the Middle River and the New River, reaching as far west as Florida's Turnpike.

Cypress Creek Canal is a conduit, spreading 3 feet of water through neighborhoods of Pompano Beach all the way west to I-95.

Central Wilton Manors could become an island surrounded by up to 3 feet of water spilling over the banks of both the Middle River and South Fork Middle River. The adjacent Coral Estates, slightly lower, would be underwater.

The New River, too, could cause havoc, with the surge submerging nearly all the neighborhoods along its path 10 to 20 blocks wide and stretching west beyond Fort Lauderdale-Hollywood International Airport, all the way past Florida’s Turnpike to parts of Davie.

The neighborhoods surrounding West Lake in Hollywood all take a hit with up to 3 feet of water, and in some areas of Hollywood and Hallandale, the surge could approach 6 feet above ground.

A 100-year rain event

As we saw with Ian’s inland flooding, storm surge is not the only story. A Category 4 hurricane can drop up to 20 inches of rain along its path.

With Ian, the wettest sector of the tri-county area proved to be in western Broward County, where the fringe of development abuts the Everglades and Francis S. Taylor Wildlife Management Area. Weston and Cooper City had close to 10 inches, while Plantation and Davie had around 8.5 inches.

But for a sense of how 20 inches of rain might affect South Florida, we can look to Hurricane Eta in 2020. The storm dumped 20.74 inches in Pembroke Pines.

Kimberly Thomason, of Southwest Ranches, raised the elevation of her yard by close to 2 feet to prevent flooding. She and her husband had moved into their community in July 2020, and a few months later, Hurricane Eta hit, leaving streets "completely submerged" and demonstrating the flood threat.
(Carline Jean / South Florida Sun Sentinel)
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The South Florida Sun Sentinel
Kimberly Thomason, of Southwest Ranches, raised the elevation of her yard by close to 2 feet to prevent flooding. She and her husband had moved into their community in July 2020, and a few months later, Hurricane Eta hit, leaving streets "completely submerged" and demonstrating the flood threat.

Kimberly Thomason and her husband moved into nearby Southwest Ranches in July 2020, and a few months later, Eta hit. “The streets were completely submerged,” Thomason said. “Eta was crazy. I was scared in my compact SUV — I thought it might float away.”

There was a foot and a half of water covering their entire 1-acre yard. Waves lapped at the tiles of their back patio. Their neighbors had similar experiences.

“We had plans on remodeling,” said Thomason of their house, which was built in 1978. “But before we did that, my husband was like, we need to make sure that this land is livable. After that storm, we were so shocked with how badly it flooded. There was about a foot and a half of water.”

So they skipped renovations and elevated their yard with dirt, more than 80 truck loads, said Thomason, to the tune of $15,000. The dirt fill was designed to prevent flooding, yet also retain water so that it can drain slowly. All told they added about 12 to 18 inches of height to their yard. “It was like initiation to the Ranches,” she said.

“Of all the things we purchased for this house, that was complete money well spent — we felt very confident this time around [with Ian] that nothing was going to flood.”

Elevating the yard did cause some consternation with neighbors, however, whose property then became the lowest point for water to settle. “If your neighbor fills and you don’t, you’re a sitting duck,” said Thomason.

She and her husband now listen in on Southwest Ranches drainage meetings, and said that they’ve bought flood insurance, even though it’s not required. “We’re not stupid,” she said.

Adorisio said that Southwest Ranches is an area of concern. “It’s probably been there since the ‘50s and ‘60s. Back then, people just built a little bit above the ground,” he said.

He points out that newer areas north and south of there, such as Weston and Pembroke Pines, were built with stricter codes and planning. “Houses in Pembroke Pines are built high, for a 100-year rainfall event, and they have pumps to move water south to the C-9 Canal.” He said that during Ida, they received more than a 100-year storm, and the system worked well.

In Palm Beach County, flood-prone areas are widely scattered throughout the county. Areas close to inland bodies of water and lower elevation areas in the northern and southern sections of the county are particularly susceptible to inland flooding, officials say.

It’s not just coastal residents who could face threats in Palm Beach County. County officials have downplayed the threat of a flood from Lake Okeechobee for the western part of the county. A county website calls the potential overtopping, which created a major flooding disaster in 1928, improbable today.

Parker, the meteorologist, is more skeptical.

“Lake Okeechobee is an enormous hazard,” she said. “There is enormous potential for devastating storm surge events with Lake Okeechobee. They’ve done a lot to shore up the dike, but it’s still not perfect. It’s an urban dike and it can be breached, and that’s very shallow water that can be pushed really hard and really far.”

Building better homes

South Florida faces a major threat for storm surge flooding, said John Renne, a professor of urban and regional planning at Florida Atlantic University.

“If you look at storm surge maps and what would flood for a Category 5 hurricane, look at Broward County,” he said. “There are a lot of homes and buildings that are potentially subject to significant flooding.”

He said after Hurricane Andrew, Florida created a strong building code to protect against wind damage, but he said it’s now time to create a uniform coastal resilience policy to identify how to protect vulnerable storm surge locations.

The mitigation measures could involve building seawalls, infrastructure, artificial islands and mangrove environments.

“The reality is, new construction located in these storm surge areas ought to be built at an elevation that would not subject those buildings to flooding during a storm surge. We need to think about how we govern new construction.”

He said right now every city has a different set of standards, which is problematic. He said a uniform set of standards could also help lower insurance rates.

He said Broward is more vulnerable than Palm Beach County, noting that Palm Beach County has about 5 to 10 feet more elevation.

Changing maps and what they mean

One way to understand the flooding threat of a Category 4 hurricane is to look at maps, but not all current maps are aligned.

That’s due, in part, to changing technology and new data. The Federal Emergency Management Agency’s current map used to determine flood zones and insurance requirements was devised based on data from a study done in the 1980s. That map will be replaced with a new one in the coming years, and though it’s not in effect yet, it’s still a useful tool for understanding South Florida’s storm risks.

The most striking difference between the old and new map in our region is the potential for storm surge well inland in south Broward, along Sunrise Boulevard west of I-95, and to areas of Cooper City and Miramar.

 Shown is a preliminary Federal Emergency Management Agency flood zone map for Broward County, which may be implemented in the coming years. Vast areas of South Broward have shifted to indicate being vulnerable to storm surge due to updated studies.
The South Florida Sun Sentinel
Shown is a preliminary Federal Emergency Management Agency flood zone map for Broward County, which may be implemented in the coming years. Vast areas of South Broward have shifted to indicate being vulnerable to storm surge due to updated studies.

Some areas, such as Miramar, have been adjusted: They’re still flooding, but in a different way, it’s more the surge being higher, instead of ponding, said Adorisio.

The FEMA map seems worse than the National Oceanic and Atmospheric Administration’s surge map, and that difference can be confusing. Adorisio sums it up in this way: The NOAA storm surge map looks at what will happen with a particular strength of storm. The FEMA map is a probability map looking at what areas have a 1% chance of flooding in any given year.

The green on the new FEMA map is associated with ponding up to 3 feet, where purple areas indicate a sheet of water that is flowing either from inland out to ocean, or a surge flowing in from ocean. “For all practical purposes, in the green, purple and red areas along the coast, water gets into the home,” said Adorisio.

Why have the FEMA maps changed so much in South Broward? “Now we have better tools — more powerful computers, more detailed information on topography and the depth of the canals, we are able to model the storm surge better,” said Adorisio. “We also have had more storms over the years from which to generate almost 500 hypothetical hurricanes [for modeling]. As a result of that, inland areas are showing higher water elevations. That coastal surge component is higher, and floods more areas.”

What the future holds

Parker said that rising seas also add major danger to storm surge.

“Climate change is a threat multiplier, and it absolutely makes storm surge more dangerous,” she said. “If the water level in advance of a storm surge event is already higher, it’s going to go even farther inland, it’s going to be even deeper. It’s going to impact more people.”

She said that’s also true during high tides and king tides.

Did Florida’s improved building codes post-Andrew help protect against storm surge? Maybe, Parker said. “That’s a difficult question. Some newer builds that had stronger codes did hold up a little better, it seems, on the west coast during Ian. But that is costly.”

She suggested it may be too risky to live on the water.

“I know that’s a difficult thing to hear for Floridians, but if you’re seriously questioning that, don’t live on the water. It’s a risk.”

“Truthfully, I would never purchase waterfront property because the odds that at some point it’s going to be destroyed by surge or rising sea levels is too high for me as a meteorologist to personally do that.”

This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative formed to cover the impacts of climate change in the state.

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