Tuesday, June 29, 2021

Rising Seas and Miami

 The exact cause of the collapse of a 12-storey building in the Miami disaster that befell the Champlain Towers South building in Surfside has yet to be fully determined, but already it 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.

It has highlighted the precarious situation of buildings 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 saltwater 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 seawater 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.”

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 onto 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.

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.”

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