When you’re either buying or renting, discovering that your home is gradually sinking is the last thing you want to hear, particularly if it’s a penthouse.
This reality has come to light for the hundreds of residents living in 35 high-end high-rise buildings and condos on Miami’s barrier islands in Florida, after a seven-year investigation into subsidence in the region.
These buildings are located across a part of Florida, with the affected structures situated in Surfside, Miami Beach, Sunny Isles Beach, and Bal Harbour. A study has discovered that these buildings have experienced subsidence in recent years.
The finding was made by a team of researchers from the University of Miami, University of Houston, Florida Atlantic University, California Institute of Technology, the GFZ German Research Centre for Geosciences, and University of Hanover in Germany.
The subsidence recorded was between two and eight centimeters, attributed to the presence of multiple heavy construction sites nearby.
The study’s abstract states: “This study utilizes Interferometric Synthetic Aperture Radar (InSAR) to examine subsidence along the coastal strip of the Miami barrier islands from 2016 to 2023. Using Sentinel-1 data, we document vertical displacements ranging from 2 to 8 cm, affecting a total of 35 coastal buildings and their vicinity.
“About half of the subsiding structures are younger than 2014 and at the majority of them subsidence decays with time. This correlation suggests that the subsidence is related to construction activities.
“In northern and central Sunny Isles Beach, where 23% of coastal structures were built during the last decade, nearly 70% are experiencing subsidence.”
The study further explained: “The majority of the older subsiding structures show sudden onset or sudden acceleration of subsidence, suggesting that this is due to construction activities in their vicinity; we have identified subsidence at distance of 200 m, possibly up to 320 m, from construction sites.
“We attribute the observed subsidence to load-induced, prolonged creep deformation of the sandy layers within the limestone, which is accelerated, if not instigated, by construction activities.
“Distant subsidence from a construction site could indicate extended sandy deposits. Anthropogenic and natural groundwater movements could also be driving the creep deformation.
“This study demonstrates that high-rise construction on karstic barrier islands can induce creep deformation in sandy layer within the limestone succession persisting for a decade or longer.
“It showcases the potential of InSAR technology for monitoring both building settlement and structural stability.”
This discovery comes over three years after the tragic collapse of Champlain Towers South, a 12-story condominium in Surfside, Florida, which resulted in the deaths of 98 people.
If you’re considering investing in a coastal property, it might be wise to hire a subsidence surveyor to examine the surrounding area… assuming you can instruct them to do so.