America's largest cities are slowly sinking due to their own weight, drought and other geological pressures, according to a study published in Nature Cities. Houston is "buckling" fastest, according to the study's interpretation of satellite data, with more than 40 percent of its land subsiding faster than 5mm a year. There, groundwater mining and fossil fuel extraction are accellerating the process; 12 percent of it is subsiding faster than 10mm a year.
Land subsidence is a slow-moving hazard with adverse environmental and socioeconomic consequences worldwide. While often considered solely a coastal hazard due to relative sea-level rise, subsidence also threatens inland urban areas, causing increased flood risks, structural damage and transportation disruptions. However, spatially dense subsidence rates that capture granular variations at high spatial density are often lacking, hindering assessment of associated infrastructure risks. Here we use space geodetic measurements from 2015 to 2021 to create high-resolution maps of subsidence rates for the 28 most populous US cities. We estimate that at least 20% of the urban area is sinking in all cities, mainly due to groundwater extraction, affecting ~34 million people. Additionally, more than 29,000 buildings are located in high and very high damage risk areas, indicating a greater likelihood of infrastructure damage. These datasets and information are crucial for developing ad hoc policies to adapt urban centers to these complex environmental challenges.
Coastal cities are put at greater risk by subsidence, with nearby sea levels rising to meet the sinking land. Carly Cassella, in Science Alert:
Meanwhile, cities like New Orleans that face flooding risks may require raised land or improved drainage systems. Urban centers at risk of uneven cracking could retrofit or introduce infrastructure to better withstand moving foundations.
"Our long-range goal is to map all of the world's coastlines using this technique," Shirzaei said in 2024.
"We know that planners in several US cities are already using our data to make our coastlines more resilient, and we want cities all over the world to be able to do be able to do the same."
Previously:
• Mexico City Metro threatened by subsidence
• Manhattan 'sinking' under the weight of all those skyscrapers
