The ground is sinking beneath many American cities, including New Orleans, New York City, Miami, and South San Francisco.
This phenomenon, known as land subsidence, can severely impact the safety of buildings and infrastructure. When combined with sea level rise, it can dramatically increase the incidence of flooding.
Problems associated with subsidence could cost U.S. homeowners 6 percent of their home’s value. In areas with significant subsidence, that number could jump to 8.1 percent, according to upcoming research by Mehdi Nemati, an assistant professor of public policy at the University of California, Riverside, and his colleagues. Their study focused on California’s Central Valley, but Nemati said the findings could be extrapolated nationwide.
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Standard homeowners insurance typically doesn't cover subsidence issues, according to Policygenius, although in some areas, you may be able to purchase specific coverage for subsidence caused by nearby mines or mining activity.
Consumers are likely to see the impact of subsidence both directly, in the form of problems with their homes, and indirectly, in the form of issues with their local economy.
What are the causes of land subsidence?
Natural and human processes cause land subsidence.
As glaciers retreat from land in the United States and Canada, the process creates a see-saw effect, with land sinking in the United States but rising in Canada, researchers say.
Manouchehr Shirzaei, a professor of geophysics and remote sensing at Virginia Tech, also attributed some of the subsidence to tectonic processes.
“For example, earthquakes can cause the ground to rise, but they can also cause it to sink in some places. So both of these processes are natural processes,” he added.
Land subsidence caused by human activities is linked to how our cities are developed, particularly groundwater extraction and construction practices.
“We use groundwater for drinking and other purposes. As we extract water from the ground, the space underneath it becomes compressed because we build on top of it,” says Rob Freudenberg, vice president of energy and environment at the Regional Planning Association. Heavy construction materials also compress the ground, putting infrastructure at risk.
When designing infrastructure, most don't take land changes into account. Experts say that could be dangerous.
“If you think of something like a railroad and the railroad tracks that run through flooded land, some of them will sink and some of them won’t,” Freudenberg said. “So you may now have some kind of erosion under the track where there wasn’t before. You may have to realign the tracks.”
Watch the video above to learn more about how subsidence is putting U.S. infrastructure in a precarious position and how much it could cost to fix it.
