Rising seas add to sinking feeling
The 12-storey condominium tower that crashed down near Miami Beach was built on reclaimed wetlands and is perched on a barrier island facing an ocean that has risen about 30 centimetres in the past century because of climate change.
Underneath its foundation, as with Miami Beach, is sand and organic fill – over a plateau of porous limestone – brought in from the bay after the coast’s mangrove forests were removed. The fill sinks naturally and the subsidence worsens as the water table rises.
Experts on sea level rise and climate change caution that it is too soon to speculate if rising seas helped to destabilise the oceanfront structure. But South Florida has been on the front lines of sea level rise, and the effects of climate change on the region’s infrastructure – from septic systems to aquifers to shoreline erosion – will be a management problem for years to come.
The Champlain Towers South building was recently found to have been sinking in the 1990s, and may have continued to sink since then, according to Shimon Wdowinski, a professor at Florida International University’s department of earth and environment, who has studied the area.
‘‘I was shocked to see it collapsed,’’
Wdowinski said.
Miami and nearby beach communities have experienced substantial sea level rise, up to 30cm over the past century, according to some estimates. That includes nearly 15cm since the mid-1990s, according to a Capital Weather Gang analysis of federal data. This has led to a 320 per cent jump in nuisance flooding in the area over the last 23 years.
The porous limestone underneath Miami allows the rising seas to filter up through the ground, causing flooding during high tides even on sunny days. The groundwater surge threatens
freshwater supplies and septic systems, which are already failing in Miami-Dade County.
The mix of swelling groundwater and tidal cycles juiced by climate change meant coastal buildings and their concrete foundations spent more time in water than they did in the past, said Albert Slap, the chief executive of RiskFootprint, a Boca Raton-based company that assesses buildings’ vulnerability to hazards such as storm surge and flooding.
‘‘This is a tragic, devastating event, and it could be a canaryin-the-coal-mine type event,’’ he said.