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ANALYSIS: What’s known about climate and the Surfside condo collapse – E&E News

Did climate change play a role in the deadly collapse of a Miami-area condominium last week?

Experts say it’s too soon to tell. At least one factor has come up as a possibility — the corrosive impact of rising sea levels — but other variables have little to do with global warming.

A more complete answer is expected in the next several months. That’s when investigators plan to finish their inquiry into the Champlain Towers South disaster, which killed at least 11 people and left more than 150 missing.

In the meantime, scientists said the danger of climate change should not be underestimated. Between sea-level rise and the growing intensity of hurricanes, global warming looms as the biggest threat to Miami and other coastal communities.

That doesn’t mean catastrophic building collapses will become common in the future. Experts say it’s exceedingly rare for a structure to become so unsafe without anyone noticing.

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But a steady increase in coastal flooding can render whole communities gradually unlivable — damaging homes, washing out roads and contaminating drinking water. That’s all punctuated by the occasional, but growing, threats posed by extreme storms.

It’s a problem Florida is intimately familiar with. Sea levels in Miami have risen by several inches since the 1990s alone. Meanwhile, major hurricanes within the last five years — including Irma in 2017 and Michael in 2018 — have killed dozens of people and racked up billions of dollars in damages.

Climate change and increased flooding “disrupts already people’s daily lives on a relatively regular basis,” said Thomas Wahl, a civil engineer and coastal risk expert at the University of Central Florida.

‘The confluence of multiple things’

Several recent reports — revealed by reporters over the last few days — have fueled speculation about what led to the collapse of Champlain Towers South, a 12-story condominium located in the town of Surfside near Miami Beach.

Surfside officials released a 2018 report on Friday that flagged “major structural damage” to the concrete slab beneath the ground-level pool deck.

The report also identified extensive cracking and crumbling in the concrete columns and walls supporting the parking garage below the building.

While it’s still unclear what caused the damage, experts have noted that structures built in salty coastal climates are vulnerable to corrosion. Concrete is a porous substance, which makes it possible for salt water to seep inside. When that happens, salt can corrode the steel rebar used to reinforce concrete structures.

Steel expands as it rusts, putting pressure on the concrete and causing little bits to crumble and flake away. It’s a process known as spalling — in severe cases, it’s sometimes referred to as “concrete cancer.”

Multiple headlines have appeared over the last few days questioning whether sea-level rise, and an increase in salty floods, might have helped corrode Champlain Towers. But so far, there’s no hard evidence to support that theory.

Reporters last week also seized on a 2020 study that found that the land beneath the condo complex had been slowly sinking during the 1990s, at a rate of about 2 millimeters per year.

The sinking is a process known as “subsidence,” and it’s common in many coastal areas — especially in places with heavily depleted groundwater resources or in areas built atop filled-in wetlands. The latter is true across much of the barrier island where Surfside and Miami Beach were built.

New Orleans, for instance, is sinking by about 5 millimeters, or a fifth of an inch, per year. Mexico City is an extreme example, sinking by up to 20 inches each year.

But although subsidence sometimes can affect the structural integrity of buildings, experts say it doesn’t often cause buildings to abruptly collapse — at least not without the influence of some other factor.

Timothy Dixon, a geologist at the University of South Florida, said subsidence tends to pose the biggest threat when the rate of sinking is not uniform beneath all parts of a structure — causing the building to tilt. It’s unclear if that was true in this case.

“I’d be surprised if subsidence was a big factor in that collapse, but of course it can’t be ruled out,” he told E&E News.

Shimon Wdowinski, a geophysicist at Florida International University and co-author of the 2020 subsidence study, cautioned in a statement that sinking doesn’t necessarily indicate an imminent risk of collapse. He noted that there were likely other factors at play, even if the sinking did play a part — “something from the engineering point of view that caused it to collapse,” he said.

Until a full investigation is complete, it’s impossible to say whether salt, sinking or other environmental variables played a role in the Champlain Towers disaster.

At the same time, some experts have noted that climate change often acts as a risk multiplier — it takes bad situations and makes them worse. That means it’s not unreasonable to question whether climate change was an accomplice.

“Planes don’t fall out of the sky for one reason. And buildings don’t fall down for one reason. It’s usually the confluence of multiple things happening at the wrong time,” said Jesse Keenan, a social scientist at the Tulane University School of Architecture.

But he added that climate change “can take a very harsh situation — it’s very harsh to live on the ocean — and compound those risks to lead to something like this.”

The ‘biggest concern’ for coastal infrastructure

Regardless of what triggered the Champlain Towers disaster, climate change poses plenty of known risks to coastal infrastructure in places such as Miami.

Subsidence is a major concern in coastal communities like Miami Beach. But its biggest danger is the threat of increased flooding, especially when paired with sea-level rise.

Sea-level rise is a growing threat to coastal communities, especially on the East Coast, where many areas are seeing their water levels rise at rates significantly faster than the global average. Tide gauges near Miami have shown that the sea level is rising by as much as 9 millimeters, or about a third of an inch, each year. That’s already about three times the global average.

In places that are also sinking, the risk of flooding is even higher.

“The land goes down as the water goes up, there’s only one outcome: We see more flooding,” said Wahl, from the University of Central Florida.

Subsidence isn’t a big issue in most of Florida. But in places where it’s happening, including parts of Miami Beach, flooding may be more severe than in surrounding areas.

Even in places that aren’t sinking, floods are a growing problem. Research has found that “sunny-day” floods — flooding that happens even when it’s not storming, often during high tide — are on the rise along the East Coast.

One Washington Post analysis found that there’s been a 320% increase in sunny-day flooding in Miami since the 1990s.

Sea-level rise also can increase the risk of corrosion in buildings and other infrastructure. As the ocean rises, salt water can creep into fresh groundwater systems, a process known as saltwater intrusion.

It’s a problem that “should be on people’s radar more and isn’t yet,” said Dixon, the University of South Florida geologist.

It’s a particular concern for water and sewage systems, Dixon said. Salt water can corrode iron and steel pipes where they lie underground. Building foundations tend to be better insulated, he added, but they could be vulnerable to corrosion if they’re exposed.

Saltwater intrusion also is a big threat to drinking water. It’s already a major concern in Miami-Dade County, where more than 2 million people rely on fresh groundwater from the Biscayne Bay aquifer.

Monitoring by the U.S. Geological Survey suggests that salt water is steadily pushing farther inland toward the aquifer.

There’s also the annual threat of hurricanes, which are becoming a bigger concern. Numerous studies have found that climate change is causing hurricanes to grow more intense, increasing the odds they’ll spin into major storms.

While strong winds are an obvious threat to infrastructure, water often is the bigger worry. Storm surge and heavy rain can combine to produce catastrophic flooding. And sea-level rise can make storm surge worse over time.

Whether from storms or from king tides, flooding “would be my biggest concern if I own property right at the coast,” Wahl said.

Keeping the streets dry comes at a hefty price. The city of Miami recently released a new stormwater master plan, which suggested it would cost around $4 billion to protect the city from the rising seas with a network of stormwater pumps, sea walls and drainage systems. Even then, the report warned, not every neighborhood would be safe.

The Army Corps of Engineers also has proposed a $6 billion sea wall to protect against storm surge, spanning 6 miles of the Miami-Dade coastline.

None of these is a perfect, or permanent, fix. Only serious efforts to halt global warming will slow the steady invasion of rising seas. But they can provide some measure of protection against the damage that’s been done already.

“I think there’s still a wide range of options available to mitigate some of these impacts and risks that coastlines will face in times of a changing climate,” Wahl said. “Of course, all of that requires money and political will.”

Reporter Avery Ellfeldt contributed.

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