Dozens of luxury condos, hotels and other buildings in Southeast Florida are sinking at a surprising rate. Almost 70% of the buildings in the northern and central part of Sunny Isles are affected, according to a study published in December by the University of Miami, the American press reports.
Miami beaches are exposed to flooding due to climate change PHOTO SHUTTERSTO
The study was initiated after the tragic Champlain Towers collapse in Surfside, which killed 98 people in 2021. However, researchers found that subsidence was not responsible for the building’s collapse. Instead, they found evidence of sinking all along the coast of Miami.
The researchers identified 35 structures that sank by up to 8 centimeters between 2016 and 2023.
These include city landmarks such as the Faena Hotel, Porsche Design Tower and Trump International Beach Resort. According to the authors of the study, almost all the buildings built on the barrier islands along the coast of Miami are in the process of sinking.
Measurements showed sinking of up to 7.6 centimeters in areas such as Sunny Isles Beach and Surfside, and some buildings in Miami Beach and Bal Harbor are also affected.
Expert Falk Amelung, lead author of the study, explained that the phenomenon is caused by a combination of factors, including the weight of constructions, vibrations from constructions, groundwater movements and tides.
“It’s not a surprise that buildings move during construction or right after, because they’re heavy, and engineers take that into account when they design,” Amelung said, but for the phenomenon to continue years afterward, “it was a surprising thing”.
Oceans rise, coasts sink
Miami faces a dual threat: land subsidence and sea level rise due to climate change, which increases vulnerability to flooding, storm surges and erosion.
“Any change in the relative height of sea level — whether the land is falling or the sea is rising — would cause significant flooding in the region,” Manoochehr Shirzaei, a geophysicist at Virginia Tech who was not involved in the study and who recently a study linking sinking cities to rising sea levels.
This sinking phenomenon, called subsidence, is happening “almost everywhere we look,” he added, according to Business Insider.
Many of the worst-hit coastal cities are in East and South Asia, but major cities in Europe, Africa and Australia are also sinking rapidly.
In the US, Shirzaei’s research group found that huge areas of the East Coast – including New York and Baltimore – are sinking at least 2 millimeters each year.
In a later study, Shirzaei’s research group found that Gulf Coast cities were sinking even more.
Despite its prevalence, subsidence is not usually considered in future flood estimates.
Combining that with sea-level rise projections, Shirzaei’s group estimated that by 2050 up to 518,000 Americans would be exposed to high-tide flooding at an additional 288,000 properties, at a cost of $109 billion.
It’s not just about flooding, though. Settlement can also compromise the structural integrity of a building.
“The situation becomes worrisome when different parts of the building move at different rates,” said study authors Farzaneh Aziz Zanjani and Falk Amelung.
“This can cause structural damage, such as cracking or distortion, which could compromise the safety of the building over time,” they added.
Satellites can survey risk areas before they sink to a critical level
When researchers at the University of Miami analyzed satellite data, they found no signs of subsidence before the collapse of the Champlain Towers in Surfside, Florida, which surprised them because there was a lot of construction going on in the area.
Subsurface limestone may be interspersed with sandy layers in barrier islands. Vibrations from construction could cause sand grains to shift and sag under the weight of the buildings.
Although there are likely other factors at play, discovering a link to the subsidence of some structures can be helpful.
Researchers are seeking funding to study sediments in Miami and investigate uneven subsidence, where different parts of a building sink at different rates.
Shirzaei said satellite remote sensing could be a diagnostic tool to scan specific regions to detect buildings leaning on uneven terrain. Investigators can then target risk points and, if necessary, suggest structural reinforcements.
