Miami’s luxury beachfront properties are sinking much faster than scientists expected

High rises are heavy, and that can cause the ground below them to slowly sink and settle, especially right after they’re constructed. But in Miami, dozens of buildings along the coast are sinking at “unexpected” rates, and long after they were initially built.

Scientists at the University of Miami found that 35 buildings along an approximately 11 mile stretch of the coast, from Miami Beach to Sunny Isle Beach, are sinking into the ground—a process known as subsidence. Researchers examined the buildings from 2016 to 2023, and found that they sank two to eight centimeters—about .8 to 3 inches. Those buildings include beachfront condos and hotels, like the Trump Tower III (which sank 4 centimeters in that time) and the Ritz Carlton Residences (5 centimeters).

The worst subsidence was in Sunny Isles Beach, followed by Surfside, where a 12-story condo building collapsed in 2021. Miami Beach saw the least amount of subsidence. To figure out just how much these buildings were sinking, the researchers used satellite images that can measure elevation, or how much a building has sunk down to millimeters. They compared hundreds of those images over time to create a “surface displacement time series.”

“The discovery of the extent of subsidence hotspots along the South Florida coastline was unexpected,” Farzaneh Aziz Zanjani, lead author of the study and a former post-doctoral researcher at the school, said in a statement. “The study underscores the need for ongoing monitoring and a deeper understanding of the long-term implications for these structures.”

In Miami, these buildings sit on limestone layered with sand. The ground is likely sinking because of how the grains of sand shift under the weight of the buildings, as well as the vibrations that happen during construction, researchers say. But daily tides and cracks in the limestone could lead to ongoing sinking. (Experts not associated with the study also told the Miami Herald that rising sea levels, a consequence of greenhouse gas emissions, could be worsening limestone erosion in the ground.)

Researchers also specifically looked at Champlain Towers South, the Surfside condo building that collapsed in 2021, to see if subsidence played a role in that catastrophe. It was the deadliest structural failure in the country, leading to 98 deaths and laws for structural reviews of condos in Florida. However, researchers said “no displacement signals were detected” before that building collapsed, meaning sinking or settlement was not the cause. (A federal investigation found issues in the concrete columns that supported the building, and construction flaws on its pool deck.)

Still, the study, published in the journal Earth and Space Science, could be a “game changer” for monitoring buildings and the stability of the ground below them going forward. Researchers say that both local authorities and the residents of such buildings should be informed about any subsidence happening, and how much, which would allow them to monitor their buildings, look for any cracks, and be proactive. While subsidence can’t totally be prevented, owners can ensure that the ground has proper drainage systems and work with engineers to reinforce a building’s foundation.

“Our hope is that officials in Florida will recognize the value for continued research on this issue across the state and explore how this novel technology can benefit coastal residents,” geophysics professor and the study’s senior author Falk Amelung said.