Dozens of luxury condos and hotels in Florida are sinking, study finds

By Rachel Ramirez, CNN

(CNN) — Dozens of luxury condos, hotels and other buildings in southeast Florida are sinking at a surprising rate, researchers reported in a recent study.

The study, led by scientists at the University of Miami, found 35 buildings from Golden Beach to Miami Beach sank as much as three inches between 2016 and 2023. The sinking buildings — which together accommodate tens of thousands of residents and tourists — include the Ritz-Carlton Residences, Trump Tower III, Trump International Beach Resorts and the iconic Surf Club Towers.

Researchers said the main cause behind the sinking was vibrations from construction, which can cause soil particles to compact and settle, resulting in subsidence – the gradual sinking of land.

The effect is like shaking ground coffee around to create more room, Falk Amelung, senior author of the study and a professor of geophysics at the University of Miami’s Rosenstiel School Department of Marine Geosciences, told CNN. But that wasn’t the startling conclusion.

“It’s not a surprise if buildings move during the construction or immediately after the construction, because it’s heavy and the engineers take that into account when they build,” Amelung said, but that it continues for years after, “that was surprising.”

Researchers began the study when the Champlain Towers collapsed in Surfside, Florida, in 2021. Although the researchers did not detect any signs of subsidence before the Surfside collapse, they did find evidence of it at nearby beachfront buildings and along the coastline.

Using satellite images to track tiny movements of the Earth’s surface, they looked at specific points of the buildings like balconies and rooftop air conditioning units and measured how they moved over time.

Nearly 70% of buildings are sinking in northern and central Sunny Isles Beach, according to the study. Around 23% of the structures in these locations were built in the past decade.

In addition to construction vibrations, daily tides that move water toward and away from the shore can also cause the ground to shift and the buildings above it to sink.

Seismic activity or soil compaction, either naturally from the weight of sediment accumulating over time or from heavy buildings pressing down on the ground, can also cause sinking – a problem in areas where new coastal land has been created over the years by backfilling with sediment.

Researchers say the findings only raise “additional questions which require further investigation.”

Oceans rising, coasts sinking

Miami faces a dual threat: land subsidence and rising sea levels due to climate change – a combination that increases the city’s vulnerability to coastal flooding, storm surge and erosion.

Land subsidence exacerbates severe flooding due to sea level rise, said Manoochehr Shirzaei, a geophysicist at Virginia Tech who was not involved with the study

“Any change in relative elevation of the sea level – whether the land goes down or sea goes up – would cause significant flooding in the region,” Shirzaei, who recently conducted a study linking sinking cities and rising seas, told CNN.

Sea level rise in the study area is unfolding at a rate of roughly 2.6 inches per decade when averaged over the past 30 years, said Brian McNoldy, a climate and weather researcher at the University of Miami, who was not involved in the study.

At these specific locations, McNoldy told CNN “the buildings are sinking as fast as the ocean is rising, effectively doubling the (sea level rise) rate at those sites.”

But Shirzaei and Amelung said there is no reason to panic, noting that the satellite method researchers used can now proactively monitor the stability of coastal high-rises.

“The good thing about land subsidence, in contrast to sea level rise, is that we can take local actions to protect us against that,” Shirzaei said. “This technology provides us with the data to create an approach similar to healthcare, but for buildings, so we can monitor them on regular basis … and make decisions before catastrophe happens.”

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