More than one fifth of New York City is built on what used to be open water, marsh or tidal flats, according to new mapping by scientists at the New York Botanical Garden. Those spots, dubbed “blue zones,” include parks, public housing, airports and entire neighborhoods that still flood now or are likely to flood as sea levels rise and storms get nastier. City planners say the overlap of historic wetlands with today’s dense development is setting up hard decisions about where to pour money into floodproofing and where, eventually, to move housing and services.
How the Map Was Made
The Garden’s researchers combined their Welikia historical ecology reconstructions with modern flood datasets to find places that once held rivers, marshes or tidal flats and that now face coastal or pluvial flood risk. As outlined by New York Botanical Garden, the team stacked Welikia maps with FEMA flood layers, Department of Environmental Protection stormwater resiliency maps and 311 flooding reports to build a digital, block by block tool. The end result is a searchable citywide map that shows exactly where past water footprints line up with present and projected flooding.
Who and What Sit in the Blue Zones
According to The City, roughly 1.2 million New Yorkers, about 12 percent of the city’s population, live in blue zones, and about 11 percent of buildings are located in them. The analysis finds that nearly two thirds of blue zone acreage faces coastal flooding risk, while other portions flood mainly from intense rainfall or from a mix of both coastal and rain driven events. The mapping also highlights that major facilities, including John F. Kennedy and LaGuardia airports, along with a large share of parks and other public land, fall inside those zones.
What Officials Are Saying
City agencies say the new map can help focus limited dollars where they will make the biggest dent in future damage. Department of Environmental Protection spokesperson Doug Auer called the blue zones work “a useful tool in collaborative stormwater planning efforts,” according to The City. Parks officials are on the same page. Judd Faulkner told the outlet that using the latest data and best practices can create “a stronger, more equitable park system that protects people and nature.”
Planning, Equity and Next Steps
Because much blue zone land is publicly owned, New York Botanical Garden’s analysis puts the share at roughly two thirds, planners argue that the city has both a responsibility and a real opportunity to protect vulnerable communities. A planning review by Cornell's CASA points to block scale data like this as the backbone for targeted green infrastructure projects, voluntary buyouts and technical assistance for multi family buildings. Advocates warn that those moves will have to come with real funding and robust community engagement in order to avoid repeating past patterns of displacement.
Bottom Line for Neighborhoods
The block by block blue zones map does not set policy on its own, but it clearly lays out where the city will need to invest to keep roads, sewers and homes functioning and where relocation planning may ultimately come onto the table. For neighborhoods in the blue zones, many of them low income or home to public housing developments, the map is a blunt reminder that earlier land use choices helped concentrate flood risk. Turning this tool into concrete protections will hinge on money, community partnership and political will.
