Big US cities are sinking

 USA Today - The nation's biggest cities are sinking, according to data from a new study.
Known scientifically as land "subsidence," the most common cause of the sinking is "massive ongoing groundwater extraction," say the study authors, though other forces are at work in some places. The cities include not just those on the coasts, where sea level rise is a concern, but many in the interior.

In every city studied, at least 20% of the urban area is sinking – and in 25 of 28 cities, at least 65% is sinking.

It's a unique study: "This is the first high-resolution, satellite-based measurement of land subsidence across the 28 most populous U.S. cities, and for several of these cities, it is the first time we have such detailed insights," study lead author Leonard Ohenhen of the Lamont-Doherty Earth Observatory told USA TODAY on May 7.

He added that the study "offers critical information for urban planning, infrastructure adaptation, and hazard preparedness."

The nation's fastest-sinking city is Houston, with more than 40% of its area dropping more than 5 millimeters (about 1/5 inch) per year, and 12% sinking at twice that rate.

Some localized spots are going down as much as 5 centimeters (2 inches) per year, according to the study.