Experts suggest vulnerability of south Florida to rising seas could lead to destabilization of further buildings

Oliver Milman – Jun 29, 2021

Hopes of finding survivors in Miami building collapse flagging – video

The shocking collapse of a 12-storey building in the Miami area last week has raised questions as to the role played by the climate crisis, and whether the severe vulnerability of south Florida to the rising seas may lead to the destabilization of further buildings in the future.

The exact cause of the disaster that befell the Champlain Towers South building in Surfside on Thursday has yet to be fully determined, although a 2018 engineering report on the structure warned of “significant cracks and breaks in the concrete” and that design flaws and deteriorating waterproofing could cause “exponential damage” via the expansion of these cracks.

At the time of the building’s sudden collapse, repairs on its roof were taking place but the restoration of concrete had not started on the 40-year-old condo. A total of 10 people are confirmed dead due to the crumpled building, with 151 people unaccounted for.

The disaster has highlighted the precarious situation of building and maintaining high-rise apartments in an area under increasing pressure from sea-level rise. Experts say that while the role of the rising seas in this collapse is still unclear, the integrity of buildings will be threatened by the advance of salty water that pushes up from below to weaken foundations.

“When this building was designed 40 years ago the materials used would not have been as strong against salt water intrusion, which has the potential to corrode the concrete and steel of the foundations,” said Zhong-Ren Peng, professor and director of the University of Florida’s International Center for Adaptation Planning and Design. “Cracks in the concrete allows more sea water to get in, which causes further reactions and the spreading of cracks. If you don’t take care of it, that can cause a structure failure.”

The geography of the area can also prove challenging for construction.

Champlain Towers South was built near the coast of what is a narrow barrier island flanked by the Atlantic Ocean on one side and Biscayne Bay on the other. Such barrier islands naturally shift position over time due to the pounding ocean, requiring a certain amount of engineering to keep them fixed in place.

Most of south Florida is just a few feet above sea level at a time when the region is experiencing a rapid increase in sea level, due to the human-caused climate crisis. Compounding this problem, the region sits upon limestone, a porous rock that allows rising seawater to bubble up from below.

This scenario means that Miami residents have become used to flooded car garages and water seeping up from drains on to roads, even on sunny days. The city is planning to build a major new sea wall to keep the ocean at bay but there is no simple defense against water rising from underfoot, placing the foundations of buildings at risk of being gnawed away by seawater.

The land beneath Champlain Towers South is also, unusually for eastern Florida, subsiding, according to a study released last year that found the condo was subsiding into the ground at a rate of around 2mm a year throughout the 1990s. Shimon Wdowinski, a professor with Florida International University’s Institute of Environment who conducted the research, said he was “shocked” to see the building collapse and didn’t immediately connect it to his study.

“It’s common that we see buildings with minor damage from subsidence, but not really this,” he said. “Things can go from stable and move slowly for a long period of time before suddenly accelerating to the point of collapse. It’s not a linear process.”

Peng said that building code upgrades in the wake of Hurricane Andrew, a category 5 hurricane that crunched into Miami-Dade county in 1992, have made new structures more resilient against major storms.

“But older buildings are still at risk and in any case the new building codes may need to be re-examined because they don’t address the issue of sea-level rise,” he said. “I think, at the very least, all new development should be required to come up with a study on the sea-level rise impact before building is done.”

The challenge for Miami, however, will continue to escalate.

The region abuts seas that are about 8in higher than they were a century ago and this pace will quicken – with another 17in of sea level expected by 2040. Depending on the melting of the vast ice sheets of Greenland and Antarctica, south Florida could be assailed by a foot of extra sea level a decade in the second half of this century, according to Harold Wanless, a geographer at the University of Miami.

“It’s going to be an enormous to impossible job everywhere to deal with that,” Wanless said. “The sea level rise is accelerating and will do so more dramatically than most people anticipate.

“Every sandy barrier island, every low-lying coast, from Miami to Mumbai, will become inundated and difficult to maintain functional infrastructure. You can put valves in sewers and put in sea walls but the problem is the water will keep coming up through the limestone. You’re not going to stop this.”