A recent study carried out by scientists from the Rosenstiel School of Marine, Atmospheric and Earth Sciences at the University of Miami (UM) has detected that 35 buildings along the coast between the municipalities of Miami Beach and Sunny Isles Beach, in Florida, are experiencing subsidence, a phenomenon in which the surface gradually sinks or settles.
The analysis, which covers the period between 2016 and 2023, revealed subsidence ranging between two and eight centimeters. The towns of Sunny Isles Beach and Surfside are among the most impacted areas.
The investigationpublished last week in the magazine Earth and Space Science used the interferometric synthetic aperture radar technique (technically known as InSAR), which uses satellite images to measure displacements at the millimeter level.
Researchers admit “constant” sinking in some cases
Falk Amelung, professor of geophysics in the UM Department of Marine Geosciences and lead author of the study, said in a written statement to the Voice of America that “subsidence in most tall buildings slows over time, but in some cases it continues at a constant rate.”
“This suggests that subsidence could persist for an extended period,” he added.
For her part, Farzaneh Aziz Zanjani, another of the researchers who participated in the study, admitted that the results were “unexpected” and warned of the “need for continuous monitoring and a deeper understanding of the long-term implications for these structures.” ”.
What is causing this collapse?
Subsidence in South Florida is linked to the region’s geology, composed of limestone with interlayers of sand. Researchers suggest that the weight of skyscrapers and vibrations during foundation construction contribute to the displacement of sand grains, causing subsidence. Additionally, daily tidal flows and possible fissures in the underlying limestone could be influencing the phenomenon.
“It is likely that there are additional factors, such as groundwater flow due to pumping during construction and daily tides, that also contribute to the subsidence,” said Khaled Sobhan, co-author of the study and professor of geotechnical engineering at the University Florida Atlantic (FAU).
Does climate change have anything to do with it?
However, some environmental entities suggest that this phenomenon is occurring as a result of the effects of climate change.
“What we suspected is being confirmed and that is that the rise in sea level, due to the rock formation of our soils and subsoils, is eroding the foundations where many of these properties and buildings that were identified by this study are located,” he explained. Yoca Arditi-Rocha, executive director of the CLEO Institute, one of the leading national organizations focusing on climate change public policy in Florida, during an interview with VOA.
Several studies carried out on the ground reveal that, since 1950, sea level has risen more than 20 centimeters in Florida, a phenomenon that, according to scientists, continues to rise.
“It is increasing and it is costing Florida billions of dollars. Not only are these properties identified by this study that are sinking, but there are hundreds of thousands of properties in Florida that are losing their value due to chronic flooding caused by the tides,” she points out, convinced that this situation “is a multiplier of risks.”
In that sense, he insists that “Florida’s soil is very porous, like Swiss cheese” and that, in his opinion, causes “water to permeate through the subsoil, to corrode,” despite the fact that scientists They have not reached a reliable conclusion on the matter.
What implications does it have for structural safety?
Although the detected phenomenon does not imply an immediate risk, scientists warn of the need to monitor the affected buildings to prevent possible long-term damage.
Despite this, Antonio Nanni, professor of civil and architectural engineering at UM, stressed that “this study is a paradigm shift” with which other similar patterns could be discovered through constant monitoring of properties.
“We now have a satellite-based method to monitor ground stability in coastal skyscrapers, which can contribute to security in this area. “It is crucial to establish a public database so that residents and authorities can monitor their buildings for signs of subsidence,” he added.
Concern among population
The publication of the University of Miami study has generated great concern among the population of South Florida. Esteban Reyes, a real estate agent in this area, confirms that several of his potential clients have expressed “some concerns” to him, especially now that the administrations have intensified policies to guarantee the correct maintenance of buildings.
All this as a result of the collapse of the Champlain Towers South building in Surfside in 2021which claimed the lives of 98 people. That case, the authors of the study clarify, is different in that the researchers did not detect signs of subsidence before the collapse, suggesting that other factors were responsible.
As a result of this collapse, the Florida government will require by law, as of January 1, 2025, that all condominiums have sufficient funds available to make repairs if necessary.
That has caused many of the homeowners’ associations to significantly increase their monthly fees to raise those funds because if the authorities discover that there is no money, they could close the building imminently.
“The timing of this report does not help either since we are seeing an increase in the cost of building maintenance, sometimes even with special increases, in addition to the increase in insurance prices, which has also been accentuated by the passage of several hurricanes in recent years,” concluded Reyes.
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