Hamptons Flood Zones and Coastal Erosion

On the South Fork shore, four layers of rules decide what an owner can build, repair or rebuild: the federal flood map, New York's Coastal Erosion Hazard Area, the town or village coastal code, and the permits that apply to the beach and the water. Each comes from a different government and answers a different question. A parcel can be clear under one and tightly limited by another.

This guide explains each layer and how to check it. Parcel-level flood and erosion data will appear on individual Hamptons pages under "Flood and coastal exposure." The physical and title questions particular to ocean land are covered in the oceanfront property guide; renovation and replacement strategy is in renovating or rebuilding.

The FEMA flood map

FEMA publishes Flood Insurance Rate Maps (FIRMs) for communities in the National Flood Insurance Program. The map divides land into zones by the chance of flooding in a given year.

The key term is the base flood: the flood with a 1-percent chance of being equaled or exceeded in any year, often called the 100-year flood. Land the base flood would cover is the Special Flood Hazard Area. The base flood elevation (BFE) is the height the water is expected to reach in that flood, shown on the map.

The zones a South Fork owner meets most often:

Outside the Special Flood Hazard Area there is typically no federal insurance requirement, but state and local floodplain rules can still apply. FEMA's own guidance notes that about a quarter of flood claims have historically come from outside it.

Reading a FIRM panel

Maps are free on FEMA's Flood Map Service Center. Each printed panel has a title block naming the community and its six-digit NFIP community number, and the panel number. Those two numbers identify which map governs a parcel.

On the coast, FEMA reads the BFE in whole feet from the panel. The elevation is measured on a stated vertical datum; a survey on a different datum needs a conversion before the two can be compared. Zone lines are drawn at map scale. A boundary crossing a lot does not tell you where it crosses the house. That takes an elevation certificate or survey.

Elevation certificates

An elevation certificate is FEMA's form showing how high a building sits relative to the expected flood level, including the height of its first floor. It is prepared by a licensed surveyor, engineer or architect. The local floodplain manager, usually in the building department, may already have one on file.

FloodSmart, FEMA's insurance site, says owners in A and V zones may need one to show the building meets local flood standards, and that it can identify premium discounts. For a buyer, it is the single most useful flood document: it ties the map to the actual building, its lowest floor, enclosures and machinery.

Flood insurance: NFIP and private

The National Flood Insurance Program (NFIP) is the federal flood insurer. In a community that participates in the NFIP, a property in an A or V zone with a federally backed mortgage must carry flood insurance as a condition of the loan.

Private flood policies also exist. Under the Biggert-Waters Act, federal banking regulators direct lenders to accept private flood insurance in place of an NFIP policy when it meets the statutory definition. Whether a given private policy qualifies is a question for the lender.

Three points for buyers:

• Zone is not price. NFIP premiums now weigh factors beyond the zone and the building's elevation relative to the BFE.
• An existing NFIP policy can sometimes be assumed by a buyer, which can carry a lower rate than a new policy.
• Get quotes before contract. The quote is current evidence of how insurers read the building.

Letters of Map Amendment

A Letter of Map Amendment (LOMA) is FEMA's written determination that a specific structure or parcel, on natural ground, would not be flooded by the base flood, even though the map shows it inside the Special Flood Hazard Area. If fill was used to raise the ground, the request is a different one: a Letter of Map Revision Based on Fill (LOMR-F).

For a building, FEMA compares the BFE with the lowest adjacent grade: the lowest ground touching the structure, including patios, stairs and deck supports. Two coastal rules matter on the South Fork:

• A building raised on posts or pilings is not removed from the Special Flood Hazard Area if any part of the structure is below the BFE.
• Anything seaward of the landward toe of the primary frontal dune may not be removed from a VE zone.

FEMA responds within 60 days of receiving complete data. A LOMA can end the federal insurance requirement, but a lender may still require coverage.

New York's Coastal Erosion Hazard Area

Separate from flood maps, New York maps a Coastal Erosion Hazard Area (CEHA) under Article 34 of the Environmental Conservation Law and its regulations, 6 NYCRR Part 505. The state has mapped the entire Long Island coastline. Inside the mapped area, building, grading, excavating, filling and most other disturbance of land need a Coastal Erosion Management Permit.

The CEHA has two parts:

• Natural protective feature areas. Beaches, dunes, bluffs and nearshore areas. The regulated area runs 25 feet landward of the landward toe of a dune, 25 feet landward of a bluff, and, on a beach with no dune or bluff behind it, 100 feet landward of the line of permanent vegetation.
• Structural hazard areas. Land behind those features where the shoreline is receding at a long-term average of one foot or more a year. The width is 40 times the annual recession rate.

The state's rules prohibit development in both areas unless a specific activity is allowed. Rebuilding is not automatic. Under the state definitions, "restoration" is rebuilding without modification at a cost of 50 percent or more of the structure's full replacement cost, and it is a regulated activity.

DEC says the current maps date from the late 1980s and are being revised. An owner can appeal a designation, but only on two grounds: the recession rate was set wrong, or the area was wrongly identified as a natural protective feature.

Who administers it

Article 34 lets a town or village take over the program by adopting a local law that DEC certifies. Otherwise DEC issues the permits. In the South Fork codes the Research Desk has read:

For the Town of East Hampton and every other coastal village, confirm with the building department or DEC's regional office whether a local program or DEC issues the permit. Other agencies, including the Army Corps of Engineers and the Department of State, can have jurisdiction over the same work.

Southampton Town's coastal rules

Southampton Town layers three sets of rules on the ocean shore.

Chapter 138. The town's coastal erosion law. Its stated purpose includes eliminating new erosion protection structures, and the replacement or reconstruction of existing ones, in the coastal area. It defines a "major addition" to a house as a 25 percent or greater increase in ground coverage, and "reconstruction" as work costing 50 percent or more of full replacement cost. Elevated walkways built under a Town Trustee permit and wood sand fencing used to build up dunes are unregulated.

The adjacent area. Zoning Article IX adds a "coastal erosion hazard adjacent area" behind the state line. West of Shinnecock Inlet it runs to Dune Road. East of the inlet it runs to the inland edge of the shoreline lot, or 400 feet landward of the hazard-area line, whichever is closer to the ocean. Regulated work there needs a coastal erosion management permit, and the article overrides conflicting zoning.

The ocean beach overlay. Zoning Article VIII bars excavation, regrading or disturbance of the dune crest on privately titled ocean beach except under an approved program, and allows one walkway across the dune: no wider than four feet, on posts, and at least three feet above the dune crest.

Tidal wetland work in the town also involves the Town's wetlands chapter and, below the high-water mark, the Trustees of the Freeholders and Commonalty of the Town of Southampton.

East Hampton's coastal rules

The Town. Article IV of East Hampton Town's zoning code governs natural resources: beaches, dunes, bluffs and wetlands. It sets coastal setbacks, including bluff and dune-crest setbacks, and lists the activities that need a natural resources special permit, with a separate administrative permit for smaller work. The town's 2006 coastal erosion overlay district divides the shore into one ocean zone and three bay zones; as summarized by the Georgetown Climate Center, new erosion control structures are allowed only in the bay zone already lined with hard structures, and repair of existing ones needs a permit.

The Village. East Hampton Village runs its own Article 34 program through the Village Building Inspector. Its law counts any increase in a structure's ground coverage as a major addition, and treats groins, jetties, revetments, breakwaters and artificial beach nourishment as erosion protection structures.

Dunes, revetments and shore structures

Across these codes, the pattern is consistent:

• Dunes are protected features, not yard. Grading, fill and construction on them are regulated; walkways and sand fencing are allowed in narrow forms.
• Hard structures are disfavored. Revetments, groins, bulkheads and geotextile tubes need permits, and Southampton Town's law aims to phase out new and replacement structures on the ocean.
• Repair and replacement are different. Normal maintenance of a functioning structure generally needs no coastal erosion permit, though Southampton Town's law still regulates maintenance of erosion protection structures. Rebuilding past the 50 percent threshold is regulated.
• An existing structure is not a permit. Ask for the approval that created it, its conditions and who maintains it.

Sea-level rise guidance

New York's official sea-level rise projections are in 6 NYCRR Part 490, updated in 2024. For the Long Island Region, the marine coast of Nassau and Suffolk, the medium projection is 18 inches above the 1995–2014 average by the 2050s and 39 inches by 2100; the high-medium projection is 21 inches and 54 inches. State agencies and applicants use these projections in programs under the Community Risk and Resiliency Act. DEC states that Part 490 itself imposes no compliance obligation on owners or local governments.

The practical point: today's flood map reflects today's conditions. A house, septic system and access road expected to last decades should be judged against the projections, not only the current BFE.

What to ask before buying

1. Which FIRM panel and zone apply, and what is the BFE or flood depth? Get the panel number and map date.
2. Is there an elevation certificate, and does it match the house as built? If not, commission one.
3. What do NFIP and private carriers quote? Can the seller's NFIP policy be assumed?
4. Is any part of the parcel in the state Coastal Erosion Hazard Area, and in which part? Natural protective feature area and structural hazard area carry different limits.
5. Which government issues the coastal erosion permit here: the town, the village or DEC?
6. Is the parcel in a town adjacent area or coastal overlay? In Southampton Town, Article IX; in East Hampton Town, Article IV and the overlay district.
7. What shore structures exist, under what permits, and who maintains them?
8. What is the flood exposure of the access road, not only the house?
9. What would rebuilding after a storm require under the current rules, not the rules that produced the current house?

The property due-diligence guide sets out the full records sequence, and the septic and wastewater guide covers the system that often limits a coastal rebuild.

Considering coastal property?

Request a private flood and coastal brief from The Roebling Research Desk: the FIRM panel and zone, elevation evidence, insurance quotes, the Coastal Erosion Hazard Area and administering authority, town or village coastal rules, existing shore structures, and the realistic paths to repair, elevate or rebuild.