A new study using satellite data has shown that New York City is sinking at a relatively rapid rate, with some urban areas collapsing much faster than others. One factor contributing to this sinking is the weight of the tallest buildings in the city, the team reported.
The team, led by US Geological Survey research geophysicist Tom Parsons, studied subsidence patterns, surface geology, and the Interferometric Synthetic Aperture Radar and the Global Positioning System (satellite data). “Geodetic measurements show an average citywide precipitation rate of 1-2mm per year, consistent with regional postglacial deformation, but we see some areas with significantly higher precipitation rates,” the team said in their work. This problem seems to be partly caused by urbanization itself.
As the team explains, “Cumulative pressure exerted on the ground by large buildings contributes to subsidence not only from initial primary settlement caused by soil compaction and reduced void space, but also from potential secondary settlement caused by creep in clay-rich layers, which can continue indefinitely.”
The team calculated the total mass of buildings pressing against the ground in New York was 764,000,000,000 kilograms. New York’s geology is complex, with different soil types. The team writes that buildings on clay-rich soil and artificial fill “are particularly prone to significant building settlement, and clay models show the greatest potential subsidence ranging from -75 to -600 mm with a median of -294 mm at a sample point in lower Manhattan.”
new YorkOther contributing factors to the collapse include hurricanes Sandy and Ida, and the team warns that repeated exposure of building foundations to seawater from hurricanes or rising sea levels can cause structural weakening, eroding steel and weakening concrete. It is emphasized that these problems will worsen with the climate crisis and increasing urbanization.
“The world’s major cities are expected to grow disproportionately to rural areas, and by 2050 an estimated 70 percent of the world’s population will be living in cities,” the team says. Major cities on every continent except Antarctica have been observed to collapse, and the problem is likely to worsen as populations grow: “Increased urbanization will likely exacerbate subsidence through groundwater extraction and/or construction intensity, which, coupled with accelerating sea level rise, means an increased risk of flooding in coastal cities. . As these trends continue, it will be important to pay attention to the accompanying mitigation strategies against flooding in growing coastal cities.”
The study was published in the journal Earth’s Future.
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