New satellite radar maps confirm what many New Yorkers have already felt in their basements and subway stations: parts of the city are slowly sinking, a few millimeters at a time, while the water keeps creeping up. The subsidence is patchy, with shoreline landfills, reclaimed stretches and old industrial fill compacting faster than surrounding ground. Add in global sea level rise, and those tiny vertical shifts start to translate into more frequent flooding on streets, in tunnels and around waterfront neighborhoods.
The issue jumped back into the spotlight this week after a short video from AccuWeather broke down the latest satellite maps for a general audience. The clip treats “sinking” as a block-by-block story instead of a single dramatic drop for the whole city, which helps explain how just a few extra millimeters can mean more nuisance flooding. It also points viewers to the same datasets that researchers and city planners are using to track where the risks are rising fastest.
The underlying analysis comes from a team at NASA’s Jet Propulsion Laboratory that used interferometric synthetic aperture radar, or InSAR, to map vertical land motion throughout the 2016 to 2023 period. As reported by NASA JPL, the region as a whole is sinking at about 1.6 millimeters per year, with some locations dropping several millimeters annually, enough to alter local flood thresholds. The team published the work in a peer-reviewed paper and released high resolution maps that let planners pinpoint where the ground is moving the most.
Sea-Level Trends: Why The Millimeters Add Up
While the land shifts, the ocean side of the equation is rising too, and has been for decades. Data from NOAA and the New York State Climate Impacts Assessment show a long term sea level rise of about 0.11 inches per year, roughly 2.9 millimeters annually, with a faster pace in recent decades and a 40 year trend closer to 0.16 inches per year. That combination of rising water and slowly sinking ground is what turns small measurements into meaningful changes in how often certain places flood.
Hotspots: Airports, Stadiums And Landfill Edges
The JPL maps flag some familiar hot spots built on artificial fill or other ground that tends to settle, including LaGuardia’s runway 13/31, which is sinking at about 3.7 millimeters per year, and Arthur Ashe Stadium, at about 4.6 millimeters per year. Portions of Governors Island, Coney Island and Rikers Island show similar issues. As NASA JPL notes, these are places where engineered fill, layers of past construction and the region’s glacial history all line up in ways that increase local flood risk. One of the study’s lead researchers put it simply, saying that the new map is detailed enough that previously unnoticed features are now standing out.
City Response: Seawalls, Raised Parks And Airport Work
Since Superstorm Sandy, New York City has been pouring money and attention into neighborhood scale defenses, from East Side Coastal Resiliency and the Big U concepts to the Lower Manhattan Coastal Resiliency projects that are now in various design and construction stages. The city’s planning materials, including the pages for the Lower Manhattan Coastal Resiliency effort, outline specific stretches of shoreline that are being elevated, bermed or lined with walls to cut near term flood risk, according to the NYC LMCR program. At the same time, the multibillion dollar LaGuardia Airport redevelopment, described in the airport’s own project documents and fact sheets, is billed as accounting for flood risk in its designs…