Data Distillery: Climate Risk and New York City’s Historic Building Stock

Mapping historic properties against stormwater flood projections

July 6, 2026

Welcome to the MAS Data Distillery, a multimedia content series demystifying timely issues pertaining to New York’s built environment. from a current planning project or city-wide issue, and present it in an easily digestible form. Each installment uses publicly available data to clarify a theme or dilemma unfolding within our city.

We analyze that data and present it here in an accessible form, focus on publicly available information that is often difficult to access or interpret, and will translate it into actionable insights that support MAS’s advocacy and help New Yorkers understand the land use decisions shaping their communities.

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As New York enters another summer storm season, extreme rainfall is once again set to put the city’s infrastructure to the test. Just weeks ago, flash flooding in parts of Brooklyn and Queens overwhelmed streets, disrupted transportation, and left vehicles stranded after intense rainfall fell in a matter of minutes. Forecasters are already warning that additional severe storms, localized flooding, and extreme heat may spell trouble for the region this summer.

This moment is important as the Mamdani administration begins advancing its “Block by Block” housing plan, which pairs ambitious housing production targets with a commitment to preserve and stabilize 200,000 existing homes over the next decade. Understanding how climate risk may affect the city’s existing building stock is therefore not only a resilience challenge, but also a housing preservation one.

An estimated 80 percent of New York City’s buildings were built before 1960, of which roughly 4 percent are landmarked.1 Older buildings already experience a host of challenges related to maintenance and repair (as MAS chronicled in A Stitch in Time Saves Nine) and environmental impacts, like those from heavy rain and flooding, are a growing threat. These structures merit protection not only for their role in the city’s historic fabric, but their contribution to the city’s housing stock, small businesses, and community spaces as well as the environmental potential in readapting instead of demolishing.2

Despite growing flood risk, preservation policy offers limited guidance for historic buildings that are not landmarked. Closing that gap begins with understanding where climate vulnerability and older building stock intersects. This question sits at the heart of MAS’s current preservation advocacy, which calls for recognizing existing buildings as a critical part of New York City’s climate resilience strategy.

Flooding affects basements, foundations, and mechanical systems in ways that compound over time. Many older structures are exempt from flood-resilient regulations, making them vulnerable to repeated damage and eventual demolition. Without standards tailored to older construction methods and materials, these buildings face cycles of damage and disinvestment that accelerate their decline. Flood damage not only harms buildings but also raises repair costs and insurance premiums, making rehabilitation less feasible over time. For many residential properties, deferred maintenance and repeated flood damage can exacerbate physical deterioration, threatening both housing quality and long-term affordability. Even landmarked buildings rarely benefit from flood resiliency guidelines that account for their unique construction and spatial constraints. Without such guidance, decisions are made on a case-by-case basis, which discourages long-term adaptation.

Although the data needed to answer these questions is publicly available, it exists across multiple agencies and formats, making it difficult for communities and decision-makers to identify patterns or compare neighborhoods. By viewing these datasets together, this analysis helps identify patterns that can inform broader advocacy conversations around climate resilience and preservation. It also reveals important patterns. First, future stormwater flooding is projected to affect thousands of New York City’s older building stock, including landmarked properties. Second, many neighborhoods facing the greatest overlap between flood risk and older building stock lie well beyond the waterfront. Finally, these datasets reveal that climate risks are not randomly distributed but concentrated in distinct parts of the city, reflecting long-standing geographic and development patterns.

Flooding in New York City is often associated with coastal storms and waterfront neighborhoods, but extreme rainfall can create a different type of risk. When heavy rain falls faster than streets, sewers, and drainage systems can absorb it, stormwater accumulates inland. To better understand how these risks may change over time, the Department of Environmental Protection (DEP) has developed projections showing where stormwater flooding is expected under future extreme rainfall scenarios. These projections distinguish between nuisance flooding, where water depth range from 4 to 12 inches, and deep-and-contiguous flooding, where water depth exceed 1 foot.

What do the maps show?

By 2080:

21% of New York City’s current buildings will be at risk of flooding in an extreme rainfall scenario. Those buildings are currently home to an estimated 2 million New Yorkers.
14% of pre-1960 historic buildings will be at risk of flooding during extreme rainfall scenarios.
22.5% of designated historic sites, including individual landmarks and historic districts, fall within the 2080 projected flood zones.
83% of buildings at risk are residential, which underscores the importance of protecting the building stock for community stability.

The landscape behind the map
The cluster of low-lying neighborhoods that scored highest in this analysis is, incidentally, south of the terminal moraine where ancient glaciers formed a range of higher elevation across Staten Island, Brooklyn, and Queens, a reminder of the interconnected, sometimes invisible systems that also play a role in climate adaptation. In their latest Statements of Community District Needs, several community boards in Central Brooklyn identified street flooding among their chief challenges. These underlying conditions continue to shape present-day flood risk, often in ways that are not immediately visible.

Why does this matter?
Making risk visible is a first step toward developing policies and infrastructure investments that help historic buildings and the communities they support remain viable in a changing climate. It also points toward several immediate opportunities for action. City agencies can use this information to prioritize flood mitigation investments in neighborhoods with high concentrations of historic buildings at risk. This includes developing flood-resilience guidance tailored to owners of older buildings, including non-landmarked properties. At the neighborhood scale, a clearer understanding of local flood risk can help community boards and advocates make the case for infrastructure improvements that reflect on-the-ground conditions.

As the City advances the “Block by Block” housing plan, these findings reinforce MAS’s call to recognize existing buildings as a critical part of New York’s climate resilience strategy. Preserving housing is not only a matter of affordability but it also requires protecting the physical buildings that make housing possible. As climate risks intensify, resilience investments will play an increasingly important role in maintaining both building quality and long-term neighborhood stability.

Methodology

How did we define “historic buildings”?

For the purposes of this analysis, “historic buildings” (as opposed to historic district buildings) are defined as structures constructed prior to 1960. This cutoff was selected to capture formally designated landmarks as well as the broader pre- and postwar building stock constructed before major zoning reforms and changes in construction typologies, which may exhibit heightened vulnerability to flooding regardless of landmark status.

How did we gather building and property data?

All information presented is derived from publicly available sources. For property-specific details, please consult the Department of City Planning’s Zoning and Land Use Application (ZoLa), which provides access to zoning, building information (via BISWEB), and property records (via ACRIS). Building data were sourced from the Department of City Planning’s Primary Land Use Tax Lot Output (PLUTO) dataset and supplemented with Department of Buildings (DOB) Building Footprints records to determine construction year.

How did we identify landmarks and historic districts?

Individual landmarks and historic districts were identified using data published by the Landmarks Preservation Commission (LPC).

How did we project future flooding conditions?

Projected flooding conditions were derived from the Department of Environmental Protection (DEP)’s stormwater flood projections for future stormwater-related flooding in an extreme rainfall scenario. DEP’s extreme rainfall scenario, with a one percent chance of occurrence per year, was selected as the most conservative representation of future stormwater flood coverage.

How did we analyze neighborhood-level risk?

To reflect the primary role of future flood exposure in shaping vulnerability, the analysis was weighted with 50 percent allocated to projected flooding, 30 percent to the concentration of historic buildings, and 20 percent to the concentration of below-grade basements in small residential buildings. Available data on basements is limited to one- to three-family buildings and there is no distinction between inhabited and uninhabited basements.

How did we calculate the number of New Yorkers living in buildings that will face flooding by 2080?

To estimate the number of New Yorkers currently living in buildings that will face future flooding, the number of units per lot was multiplied by the average household size across each borough. For buildings that shared a lot but faced different flood risk, relative building footprint size and height were used to assign the estimated number of units per building. Only buildings with footprints that intersected the 2080 extreme rain scenario flood layer were counted.

If you have questions about how this information has been represented or analyzed, please contact us at planning@mas.org.

Additional Links

MAS’s Greener Corridors initiative explores policy solutions to flooding and extreme heat along New York City’s busiest roads.
Living Above the Street, a 2023 research study by Columbia University researcher Ziming Wang that examines historic resources in New York City’s 1% and 0.2% floodplains.

¹ Analysis conducted by the Municipal Art Society using Department of Buildings (DOB) Footprints records and Landmarks Preservation Commission (LPC) data.

² Carbon emissions savings from reuse vary by individual building. The initial construction contributes significantly to a building’s lifecycle emissions. See: National Trust for Historic Preservation.