water is at the center of a new “Blue Zones” approach to understanding flood risk in New York City—an inflection point driven by the realization that flooding can reappear where the landscape historically held it. The idea is straightforward but consequential for planning: places that used to be wet can become wet again, and the overlap of past, present, and future flood signals can help identify where adaptation opportunities may be most urgent.
What Happens When water returns to historical wet places?
The turning point described by the New York Botanical Garden (NYBG) begins with a lived observation from Lucinda Royte, Manager of Urban Conservation Data, Tools, and Outreach at NYBG. Her interest intensified in 2021 after the remnants of Hurricane Ida produced an unprecedented 3. 15 inches of rain in a single hour—overwhelming infrastructure built to handle around 1. 75 inches. Walking home across what used to be Gowanus Creek, she encountered calf-deep sewage water from overflowing catch basins around the Gowanus Canal.
Reviewing maps of where flooding occurred, Royte recognized a recurring pattern: flooding returning to places that had historically been wet. She draws a distinction between two different flood reactivations across recent events. During Hurricane Sandy in 2012, coastal flooding returned to landfilled saltmarshes. Ida, by contrast, revived upland ponds, streams, and freshwater marshes. That contrast matters for how flood vulnerability is conceptualized—beyond the coastline and into areas shaped by older hydrology and topography.
NYBG’s “Blue Zones” framing focuses on the intersection of wetness across time: areas that were wet in the past, are wet in the present, and are projected to be wet in the future. The goal is to provide actionable information about causes of flooding to urban planners facing what the paper characterizes as dual crises: climate change and housing shortages.
What If the best flood map is the one that combines past, present, and future?
This week, the paper “Blue Zones: Identifying Adaptation Opportunities Using Past, Present, and Future Flooding in New York City” was published in the Annals of The New York Academy of Sciences. The work is rooted in an extended mapping and reconstruction effort led by Dr. Eric W. Sanderson and the Urban Conservation team at NYBG, building a comprehensive ecological history dataset of 17th-century New York City.
The dataset reflects an already 20-year-long process of georeferencing and digitizing maps, synthesizing datasets, and running spatial analyses. NYBG describes the outcome as a reconstructed view of the topography, hydrology, and geology of the land that would become New York City, including plant and animal species lists for each mapped ecosystem and information on where the Indigenous Lenape people lived, hunted, gathered, and farmed.
After reaching consensus on “places that used to be wet, ” the team compared those historical maps to multiple present-day and future-oriented flood datasets. For current flooding, the paper draws on four datasets:
| Timeframe | Datasets used in the Blue Zones analysis |
|---|---|
| Past flood risk | Reconstructed distribution of freshwater, intertidal, and marine ecosystems (c. 1609), based on NYBG’s ecological history dataset |
| Present flood risk | 311 service call system; New York Department of Environmental Protection (DEP) Stormwater Flood Maps; FEMA Preliminary 100-year floodplain; Hurricane Sandy inundation zone |
| Future flood risk | DEP moderate and extreme stormwater projections with sea level rise; FEMA 500-year floodplain |
| Blue Zones | Intersection of past, present, and future flood risk at the block level |
The future component explicitly incorporates DEP stormwater projections alongside sea level rise and FEMA’s 500-year floodplain. The paper frames this as an important addition because climate change is expected to increase both the frequency and intensity of storms like Sandy and Ida.
What Happens When planners treat “wet again” as a planning constraint?
A central driver of the work is institutional: NYBG notes that, with a push from the New York Department of Environmental Protection, the team began to seriously consider historical hydrology and topography when predicting flood-vulnerable areas. In practice, that means moving beyond the idea that flood risk is only a product of modern drainage, recent development patterns, or isolated hazard layers—and instead testing the hypothesis that “wet places will be wet again. ”
The “Blue Zones” concept translates that hypothesis into a practical mapping output: block-level areas where the signal repeats across time. NYBG’s post also points to a case study at the border of Brooklyn and Queens, visualizing (a) past flood risk, (b) current flood risk, (c) future flood risk, and (d) Blue Zones in one framework.
In newsroom terms, the significance is less about a single storm and more about a method. By aligning historical ecology with contemporary service calls, agency maps, and federal floodplains, the paper positions flood risk as a layered, time-spanning phenomenon—one that can complicate decisions in a city navigating climate pressures alongside housing constraints.
What If New York City’s next adaptation choices are decided block by block?
The “Blue Zones” approach does not promise certainty, and the NYBG framing is careful to describe it as identifying “adaptation opportunities” rather than predicting exact outcomes. Still, the work offers a clear organizing principle for what to prioritize: places where past, present, and future risk overlap deserve special attention because multiple independent lenses point to the same vulnerability.
In practical terms, this narrows the question for decision-makers from “Where might flooding happen?” to “Where does the landscape keep expressing the same pattern?” The implication is not that every area will flood the same way, but that persistent wetness—revealed through historical reconstruction and modern datasets—can be a credible signal for targeting planning and resilience measures.
For readers, the key takeaway is that flood risk is not only a forward-looking projection. It can also be a rediscovery of old systems—streams, ponds, marshes, and coastal wetlands—that were modified, filled, or built over, then reassert themselves under extreme rainfall and surge conditions. Understanding how those layers intersect is the value proposition of the Blue Zones framework, and it reframes how water should be anticipated in the city’s planning conversations.
