Flood Insurance in Portsmouth, NH: The South End, the Mill Ponds and Sagamore Creek

By Jon Merwin, Founder and CEO

Our office is on Islington Street, so Portsmouth flooding is not abstract to us. When a winter storm lines up with a big astronomical tide, water comes up through Prescott Park and onto Marcy Street, over the edges of the South Mill Pond and into the low streets of the South End, the same neighborhoods that hold the city’s oldest houses. The city’s own hazard plan calls flooding the most common hazard Portsmouth faces. Yet only a small share of Portsmouth buildings carry flood insurance.

This page puts the city’s records next to the insurance questions we hear from Portsmouth owners. We are a family-owned independent agency that has been in Portsmouth since 2005. We place flood coverage through the National Flood Insurance Program and private flood carriers, alongside the home policies we write with 40+ carriers. The number to reach us is (603) 431-4020.

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Where Portsmouth floods

The city’s 2024 hazard mitigation plan update lists six places as being at risk of recurring flooding or with high potential for future flooding: North Mill Pond, South Mill Pond, the South End, Peirce Island, Little Harbour and Sagamore Creek (Portsmouth Hazard Mitigation Plan Update 2024, draft). The plan notes that these areas hold Strawbery Banke, the Historic District and the downtown business district. It also notes that some places outside FEMA’s mapped zones flood too.

Area	What drives the flooding	Typical homes
South End and Prescott Park	Storm surge on top of high tides along the Piscataqua	18th- and 19th-century houses, many with low basements
South Mill Pond	Tidal water rising over the pond’s edges; heavy rain that cannot drain at high tide	Older homes and condos on the surrounding streets
North Mill Pond	Tidal flooding and rain backing up through outfalls	Converted multifamily houses and newer infill condos
Peirce Island and Little Harbour	Open exposure to surge and waves at the river mouth	Waterfront houses, some of high value
Sagamore Creek	Tidal creek flooding toward Route 1A and the back channels	Waterfront and near-water single-family homes

The table is a guide to the risk the city describes, not a flood zone determination. Two houses on the same street can sit in different zones, and elevation matters more than the street name.

The tide floods of 2022 and 2024

The hazard plan gives a short record of recent events. On December 23, 2022, a winter storm arrived at peak high tide and pushed a storm surge of nearly three feet. The Seavey Island tide gauge near the mouth of the river peaked at 12.5 feet, a full foot above flood stage. On January 13, 2024, a 9.6-foot high tide, a two-foot surge, an inch of rain with snowmelt and 30 mph winds flooded roads and property downtown and in low-lying neighborhoods. Strawbery Banke Museum saw flooding the plan calls unprecedented, with damage to historic buildings. Storms in July 2023 and March 2018 also caused extensive flooding (Portsmouth HMP 2024).

None of those storms was a hurricane. That is the point Portsmouth owners most often miss: in this city, the floods that do damage tend to come from ordinary winter storms that happen to line up with a high tide.

Few policies, older buildings

The city’s NFIP numbers, drawn from the NH Office of Planning and Development in June 2024, are worth reading closely:

• 132 policies in force across the whole city, with about $41.6 million of coverage.
• 82 of those policies are on pre-FIRM buildings, built before Portsmouth’s first flood map in 1982; 50 are on newer buildings.
• 71 cover single-family homes, 15 multifamily buildings, 28 other residential buildings and 18 non-residential buildings.
• 40 paid losses since 1978, and five repetitive-loss buildings.

For a city of Portsmouth’s size, with this much tidal shoreline, 132 policies is a small number. It suggests that many owners in the mapped areas either have no mortgage or have never been asked to buy flood coverage, and that many owners just outside the lines have never considered it. Our post on basement flooding and homeowners insurance covers the general rules; the rest of this page is about Portsmouth.

The Extended Flood Hazard Area: Portsmouth’s extra line

Portsmouth’s Floodplain Overlay District covers two kinds of land: FEMA’s special flood hazard areas and the city’s own Extended Flood Hazard Area (City of Portsmouth floodplain regulations). The extended area is land next to a FEMA flood zone that is less than two feet above the zone’s base flood elevation. When the Planning Board took up the change in 2019, staff explained that two feet matched the city’s sea-level rise projection for 2050, and that new construction in the extended area must sit at least two feet above the base flood elevation (Planning Board record, Sept. 19, 2019). The 2024 hazard plan says the city is planning for 1 to 1.7 feet of sea-level rise by 2050.

The same round of changes lowered the city’s threshold for a “substantial improvement” from 50 to 40 of every 100 dollars of a structure’s value, counted cumulatively, while leaving substantial damage at the federal 50 (Article 6 floodplain amendments, Planning Board redline, Sept. 2019; Planning Board record). In plain terms, a large renovation of an older house in the overlay can trigger flood-zone construction rules sooner in Portsmouth than in many towns. That affects renovation budgets, and it is also a reason to update your dwelling limit and your flood policy when a project ends. Confirm the current rules with the city before you plan work.

What a Portsmouth flood policy needs to handle

A few local features come up again and again when we quote flood coverage here:

• Basements. NFIP building coverage in a basement is limited to items such as the furnace, water heater, electrical panel and foundation, and it does not cover finished walls, flooring or most belongings stored there. A finished South End basement is a common surprise.
• Replacement cost versus actual cash value. The NFIP pays replacement cost on a single-family primary residence only when it is insured to at least 80 of every 100 dollars of its replacement cost (or the program maximum). Otherwise it pays actual cash value. Second homes and condos are handled differently.
• High rebuild costs. Many Portsmouth houses cost far more than $250,000 to rebuild. Excess flood sits above an NFIP policy; a private flood policy can replace it.
• Condos. Many downtown and Mill Pond condo associations carry a master flood policy, but unit owners may still want coverage for their own improvements and belongings. Our Portsmouth condo insurance page goes through it.
• Rentals. Landlords need building flood coverage on their own policy, and tenants need their own contents coverage. See Portsmouth landlord insurance.

NFIP and private flood: how we compare them

New NFIP flood policies go through Selective, and we compare that option with private flood from Flow Flood, Neptune Flood, Beyond Floods, The Flood Insurance Agency, CatCoverage and Aon Edge. Private and excess policies can offer higher building and contents limits, shorter waiting periods with some carriers, and coverage for additional living expenses, which the NFIP does not provide on a standard policy. The NFIP still has advantages, including continuity if you sell and a buyer wants to assume the policy. We lay out both on the same page so you can see what each one pays for.

Flood is one piece of a waterfront house. For the home policy itself, see Portsmouth homeowners insurance and, for larger homes, high-value home insurance in Portsmouth, where Chubb and Cincinnati each write homes at any dwelling limit. For older houses, our older and historic home insurance page explains how carriers look at plaster, slate and original trim. The December 11 flood insurance deadline post explains what to do if your NFIP renewal is coming up.

Before the next storm tide

• Look up your address on the FEMA map and the city’s MapGeo viewer, and note whether you are in the Extended Flood Hazard Area.
• Find or order an elevation certificate. It is the single most useful document a flood underwriter can see.
• Photograph the basement, utilities and contents now, so a claim does not depend on memory.
• Move valuables and records above the basement, and raise what you can of the furnace, water heater and panel.
• Buy early. NFIP coverage usually starts a month after purchase, so waiting for a forecast is too late.

More for Portsmouth and the Seacoast

Neighbors along the coast have their own pages: the Seacoast NH insurance hub, Hampton flood insurance, New Castle high-value homes and Rye high-value homes. Owners upriver can read about the new FEMA maps for Dover, Durham and the Piscataqua. Everything else we write in the city is on our Portsmouth, NH insurance agency page, and our general flood insurance page has the basics. If you want to know who you would be working with, start with our founder, Jon Merwin.

Get a Portsmouth flood insurance quote

Send the address and anything you have on the house, including an elevation certificate if one exists, and we will compare NFIP and private options for it. We don’t charge any fees. If water does get in, we help you open the claim and stay in touch with the adjuster until it is settled. Request a quote. There’s no obligation to buy. The form is just below; you can also start from the quotes page, phone (603) 431-4020 or write to insure@portsmouthatlanticins.com. Office hours run Monday to Thursday from 9 AM to 5 PM and Friday from 8 AM to 4 PM, Eastern time. Owners across the Seacoast and beyond have given us 1,000+ Google reviews and over 2,000 testimonials.

Frequently asked questions

Is my Portsmouth house in a flood zone?

Start with the FEMA Flood Map Service Center, which is the official source, and then check the city’s MapGeo viewer, which also shows the city’s Extended Flood Hazard Area (City of Portsmouth floodplain regulations; FEMA Map Service Center). Portsmouth’s current flood maps took effect January 29, 2021. If you send us the address, we will look it up with you and explain what the zone means for a policy.

What is the Extended Flood Hazard Area?

It is a city zoning layer, not a FEMA zone. Portsmouth defines it as land next to a FEMA special flood hazard area that sits less than two feet above that area’s base flood elevation, and new construction there has to be built at least two feet above the base flood elevation. The city picked two feet to match its sea-level rise planning for 2050 (Portsmouth Planning Board record, Sept. 19, 2019). A lender may not require flood insurance in that area, but the risk is close by.

Does my homeowners policy cover flooding from a storm tide?

No. Standard homeowners and condo policies exclude flood, including storm surge and high tides that come over the bank. Water backing up through a drain is a separate question again; some policies add limited coverage for it by endorsement. Our sewer backup guide explains the difference.

How much flood coverage can I buy through the NFIP?

For a home, the National Flood Insurance Program tops out at $250,000 on the building and $100,000 on contents. Many Portsmouth houses are worth far more than that to rebuild, especially older homes in the South End and along Little Harbour. Private flood and excess flood policies can provide higher limits, and some include coverages the NFIP does not.

Is there a waiting period for flood insurance?

Yes. NFIP coverage usually begins a month after you buy it; one common exception is coverage bought because a lender requires it at a loan closing. Private flood carriers set their own waiting periods. Because nor’easters and king tides arrive on short notice, it pays to buy before you see a storm on the forecast.

My historic house was built long before the flood maps. Does that matter?

It can. Of the 132 NFIP policies in Portsmouth in mid-2024, 82 were on pre-FIRM buildings, meaning they were built before the first flood map. Older buildings often have low basements, stone foundations and utilities below grade. That affects how a carrier looks at the policy and what it pays for, so an elevation certificate and good photos of the basement are worth having.

What do you need to quote flood insurance on my Portsmouth home?

The address, the year built, the foundation type and whether there is a basement, where the furnace, water heater and electrical panel sit, any elevation certificate, any prior flood claims, and your current homeowners declarations page. Request a quote. There’s no obligation to buy. Use the form below, our flood quote request or phone (603) 431-4020.

Sources

• City of Portsmouth, Hazard Mitigation Plan Update 2024 (draft with maps): flood areas, 2022 and 2024 events, NFIP statistics, sea-level rise planning
• City of Portsmouth, Floodplain Regulations (Zoning Ordinance §10.620)
• Portsmouth Planning Board record, Sept. 19, 2019 (Extended Flood Hazard Area and two-foot standard)
• City of Portsmouth, Article 6 Flood Plain District amendments, Planning Board redline draft, Sept. 2019 (definitions; substantial improvement threshold)
• FEMA Flood Map Service Center
• FloodSmart (National Flood Insurance Program)

General information for Portsmouth, New Hampshire property owners. Nothing here is a flood zone determination, a binder, a coverage promise or legal advice; what a policy pays turns on its wording and the carrier’s underwriting. City ordinances, FEMA maps and NFIP rules change over time. For your own address, phone (603) 431-4020.