Cohasset, MA Flood Zones: FEMA Basics
Cohasset covers 31.4 square miles in total, but only 9.8 of those square miles are land -- the remaining 21.7 square miles, or 68.9% of the town, is water. That makes Cohasset the most water-dominant town in this South Shore cluster, more so even than Scituate's own already-unusual roughly 45% water share. The town's coastline is not one continuous beach front but a deeply indented, rocky, ledge-strewn shore wrapped around Cohasset Cove, "The Gulf," Straits Pond, Little Harbor, and Cohasset Harbor itself, with offshore hazards like Grampus, West Shag, East Shag, Minot's Ledge, and several other named ledges sitting just beyond it. This page explains how FEMA flood zones work in general, is direct about what could not be confirmed for Cohasset specifically in the research behind it, and points to where to pull a current, address-specific determination rather than guessing from geography alone.
FEMA Flood Zones, in Plain Terms
A FEMA flood zone is a designation shown on a community's Flood Insurance Rate Map (FIRM), used for insurance underwriting and building-code purposes -- not a description of how a place felt in the last storm anyone remembers. The letters that matter most along a coastline like Cohasset's are Zone X (minimal-hazard areas outside the mapped 1%-annual-chance floodplain, with no federal mandatory flood-insurance requirement, though a lender can still require it), Zone AE (the mapped 1%-annual-chance, or "100-year," floodplain, tied to a specific Base Flood Elevation), and Zone VE (the coastal high-hazard "wave action" zone, reserved for shoreline directly exposed to storm-driven waves, carrying the strictest construction rules -- elevated construction on pilings, no habitable space below the base flood elevation).
These zone lines are not permanent. FEMA periodically remaps communities as shoreline conditions, elevation surveys, and storm modeling change, so a parcel mapped one way on an older FIRM is not guaranteed to hold that designation on the current effective map. Nothing on this page assigns a zone to any specific Cohasset street or address -- for that, use FEMA's own current map, covered at the end.
A Town That Is Two-Thirds Water
Cohasset's 68.9% water share is worth sitting with for a moment, because it changes what "coastal exposure" means here compared with a town where the ocean is one edge of a much larger land area. With only 9.8 square miles of land carrying the town's population, homes, and infrastructure, a much larger share of Cohasset's built environment sits within reach of tidal water, coves, and ponds than in a more land-heavy neighbor. The town's named water features -- Cohasset Cove, "The Gulf," Straits Pond, Little Harbor (which contains Beach Island), and Cohasset Harbor -- are not scattered curiosities on a map; together with the open Atlantic and the rocky offshore ledges beyond them, they wrap around most of the town's land mass.
That same rocky, ledge-strewn coastline is also a genuine navigational hazard, independent of flood-zone mapping: offshore formations including Grampus (site of the 1849 wreck of the emigrant brig St. John), West Shag, East Shag, Hogshead Rock, Minot's Ledge, Black Ledge, Sutton Rock, and Gull Ledge have a documented history of shipwrecks going back centuries. That history does not by itself determine any parcel's FEMA zone, but it is a useful reminder that Cohasset's relationship with the water is old, serious, and shapes how the town thinks about its coastline generally.
Cohasset's Specific Flood-Zone Designations Are Not Confirmed -- Do Not Assume
Here is the honest state of things: the research behind this page could not confirm which FEMA Special Flood Hazard Area zones -- AE, VE, or otherwise -- apply to Cohasset's coastal parcels. A direct attempt to pull the town's own "FEMA Flood Maps" page failed with a rate-limit error during that research pass, and no other source in that pass substituted a reliable zone-by-zone picture for Cohasset specifically.
That matters because it would be easy, given how this cluster's other towns have been documented, to assume Cohasset's coastal property sits in AE and VE zones the same way Scituate's has been described, or that Cohasset shares a Community Rating System class with a neighboring town. Neither assumption is supported here. Do not treat Scituate's AE/VE framing, or Marshfield's confirmed Class 7 CRS rating, as applicable to Cohasset without independent confirmation -- Cohasset has not been shown to share either. The right next steps are to retry the town's own FEMA Flood Maps page directly, or to check FEMA's own current Community Rating System community list, rather than borrow a neighboring town's figures.
What the Town Has Named as Vulnerable
Separate from any specific zone designation, Cohasset's own coastal-resilience planning work names several locations as flood-vulnerable, and those are worth knowing even without a parcel-level FEMA determination attached to them. The town's Wastewater Treatment Plant and Influent Pump Station, located in Jacob's Meadow, is one of the specific pieces of infrastructure the town's own resilience materials call out. Cohasset Cove, the James Brook watershed, Summer Street, and Cohasset Harbor itself are also named as areas of flood-pathway concern in that same planning work.
That resilience work has been backed by real, dated state funding: two Massachusetts Coastal Zone Management Coastal Resilience Grants in fiscal year 2024, totaling $447,770, aimed specifically at wastewater-infrastructure flood resiliency and at mitigating flood pathways in the James Brook watershed, building on an earlier 2022 vulnerability-assessment award of $161,925. That is a real, if state-level rather than FEMA-level, signal that the town itself treats these specific areas as its highest-priority flood-exposure points -- distinct from, and not a substitute for, an actual FEMA flood-zone map designation.
How to Actually Check a Cohasset Parcel
Nothing above -- the 68.9% water share, the named offshore ledges, or the town's own list of vulnerable infrastructure -- substitutes for a parcel-specific FEMA determination, and none of it should be read as confirming a zone for any particular Cohasset address. For that, go directly to FEMA's Map Service Center (msc.fema.gov), enter the property address, and pull the current effective Flood Insurance Rate Map panel. That lookup will show whether a given parcel falls in Zone X, Zone AE, Zone VE, or another designation, along with the Base Flood Elevation where one applies.
From there, confirm any building, elevation, or floodplain-management requirements directly with the Town of Cohasset's own Building Department, and check the town's FEMA Flood Maps page for current effective-map information (retrying it if a rate-limit or server error blocks the first attempt). If you are evaluating a specific purchase near Cohasset Cove, Little Harbor, Straits Pond, or anywhere along the harbor, a flood-zone determination from a title company or flood-certification service, ordered as part of a mortgage closing, and a conversation with a local, Cohasset-familiar insurance agent about AE- and VE-zone premium options are both worth doing before you are under contract, not after.
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Get a Free Agent Referral →Independent research. No ads. No sponsored listings. General FEMA flood-zone category descriptions (Zone X, Zone AE, Zone VE) and the Community Rating System reflect publicly documented National Flood Insurance Program definitions and are not specific to any Cohasset parcel. Cohasset's geography (31.4 square miles total, 9.8 square miles land, 21.7 square miles / 68.9% water) and named water features (Cohasset Cove, "The Gulf," Straits Pond, Little Harbor, Cohasset Harbor) and offshore ledges (Grampus, West Shag, East Shag, Hogshead Rock, Minot's Ledge, Black Ledge, Sutton Rock, Gull Ledge) reflect town and historical sources. The named vulnerable locations (the Wastewater Treatment Plant and Influent Pump Station in Jacob's Meadow, Cohasset Cove, the James Brook watershed, Summer Street, Cohasset Harbor) and the FY24 Massachusetts CZM Coastal Resilience Grant figures ($447,770 combined, building on a 2022 award of $161,925) are drawn from the Town of Cohasset's own coastal-resilience planning materials. Deliberately not included, because it could not be confirmed in research: Cohasset's specific FEMA Special Flood Hazard Area zone designations (AE/VE) and its Community Rating System class -- a direct attempt to fetch the town's own FEMA Flood Maps page returned a rate-limit error during that research pass. Do not assume Cohasset shares Scituate's AE/VE framing or Marshfield's confirmed Class 7 CRS rating; neither has been shown to apply here. This page is general education, not a flood-zone determination -- for an address-specific FEMA flood zone, use FEMA's Map Service Center (msc.fema.gov) directly, retry the Town of Cohasset's own FEMA Flood Maps page, or check FEMA's current Community Rating System community list, and confirm floodplain-management requirements with the Town of Cohasset's own Building Department.