The land beneath many U.S. cities is sinking, including New Orleans, New York City, Miami and South San Francisco.
This phenomenon, known as land subsidence, can have serious implications for the integrity of buildings and infrastructure and, combined with rising sea levels, could significantly increase the incidence of flooding.
Subsidence-related issues could cost U.S. homeowners as much as 6% of their home’s value. In areas with high levels of subsidence, that figure could jump to 8.1%, according to a soon-to-be-published study by Mehdi Nemati, an assistant professor of public policy at the University of California, Riverside, and his colleagues. While the study focused on California’s Central Valley, Nemati says the results apply nationwide.
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According to Policygenius, standard homeowners insurance policies don’t typically cover subsidence issues, but depending on your area, you may be able to purchase special coverage for subsidence caused by nearby mines or mining activities.
Consumers are likely to see the effects of subsidence both directly, through problems in their homes, and indirectly, through problems in their local economies.
Causes of land subsidence
Land subsidence is caused by both natural and man-made phenomena.
As glaciers retreat from landmasses in the US and Canada, a “see-saw” effect is occurring, with US landmass sinking and Canadian landmass rising, the researchers say.
Manouchehr Shirzaei, a professor of geophysics and remote sensing at Virginia Tech, also believes some of the subsidence is due to tectonic shifts.
“For example, earthquakes cause the land to rise, but in some places [make it] “It’s autumn. So these two are considered to be natural processes,” he said.
Man-made subsidence is linked to urban development methods, such as groundwater pumping and building methods.
“We use groundwater for drinking water and other uses, and when we pump water off the land, we’re building on it, so the space underneath is stressed,” said Rob Freudenberg, vice president of energy and environment for the Regional Plan Association. Heavy building materials also stress the land, putting infrastructure at risk.
Most infrastructure is not designed to accommodate land shifts, which experts say is dangerous.
“Think of it like a railroad track running over subsiding ground. Some of the track will sink and some won’t,” Freudenberg says. “So erosion may be happening underneath the track where there wasn’t any before. The track may need to be realigned.”
Watch the video above to learn how subsidence is putting America’s infrastructure at risk and how much it would cost to fix it.
