Viewpoints Explained: Sinking Cities: What’s Causing The Ground To Drop

This is Viewpoints Explained…

From coast to coast, there’s a shift happening, and it’s not a positive one. A study published in the journal Nature Cities last month reveals that all twenty-eight of the biggest U.S. Cities are experiencing sinking. In nearly all of the cities, two-thirds of the land mass is affected. The formal term for this is called land subsidence. And it’s not just coastal regions. It’s taking place in the Midwest and far inland too.

To reach these conclusions, researchers turned to satellite data, analyzing hundreds of pictures of ground levels between 2015 and 2021. The data showed that Houston, Texas is the fastest-sinking city with more than 40 percent of its land area dropping by faster than five or more millimeters per year. Other places at the top of the list include New York, Chicago, Los Angeles, Phoenix, Philadelphia, San Antonio, and Dallas.

You might read five or ten millimeters and think, “That’s nothing” but the compounding effect over time can compromise the structural integrity of buildings, bridges and roads. Lowering land elevations also increases the risk of flooding, especially in coastal areas already dealing with sea-level rise.

So, what’s the main culprit? Scientists point to excessive groundwater extraction. As cities pump water from underground aquifers to meet growing demands, the land above compresses and sinks. With population growth and intensifying climate change, study researchers believe the sinking itself may be unavoidable, but the damage doesn’t have to be. This information should be used to adapt current building codes and practices as well as create wider-scale solutions that may be able to slow this deterioration. This change is hard to see, but it’s one that we can’t afford to ignore.