NYC Hidden Flood Risk

Buildings near modeled rainfall flooding that sit outside FEMA's flood zones, where flood insurance isn't required and risk is easy to miss.

How to read this map: data, methods & glossary ↗

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    – hidden-risk buildings (–% of NYC)
    – of those exposed in a moderate storm today
    – likely basement homes at hidden risk
    – Ida sewer backups on model-flagged lots vs. chance

    Zoom in to see individual buildings.

    Buildings

    • Hidden risk: exposed today, outside FEMA zones
    • Hidden risk: exposed only in 2050 / 2080 storms
    • Flood-exposed, inside a FEMA zone
    • Not exposed

    Layers

    Top neighborhoods

    Top neighborhoods by the selected shading metric
    NeighborhoodValue
    About the data

    Flood-exposed: NYC DEP's Stormwater Flood Maps show 4 in or deeper ponding within 5 ft of the building footprint. The maps cut building outlines out of the flood polygons, so exposure is measured at the footprint edge.

    FEMA zones: 2015 Preliminary FIRM, 1% (VE/AE) and 0.2% annual-chance zones. A building counts as inside if any part of it touches a zone.

    Likely basement home: a 1–2 family home that NYC Finance records as having a below-grade basement. It's a proxy, since no public dataset lists basement apartments.

    Sources: NYC Open Data (building footprints, MapPLUTO 26v2, Stormwater Flood Maps, 311, 2020 NTAs), FEMA. Basemap © OpenFreeMap, © OpenStreetMap contributors.