Blog · October 14, 2026 · New Hampshire
Coos County Flood Zone Map, New Hampshire
How to check whether a property in Coos County sits in a FEMA flood zone, and what the answer means for a buyer near Berlin.
Main page: Coos County, NH GIS & Parcel Viewer (official map link, Coos County facts and neighboring maps).
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A Coos County flood zone map check belongs in the due diligence for any Coos County property, from a house lot in Clarksville to farm ground near Lancaster. Here's how to read FEMA's map for a Coos County, NH property and match it to the parcel record.
Below are the FEMA links, a plain reading of the zone labels, notes on where water shapes land around Clarksville, and short answers to common questions.
Where to see the official Coos County flood zone map
Start at the FEMA Flood Map Service Center and enter the property address in Berlin or anywhere else in the county. If a tract near Dalton has no street number yet, search the nearest road and pan to it. On acreage outside Berlin, FEMA's National Flood Hazard Layer viewer draws the zones over aerial imagery; zoom to the tract near Dalton and click. Next, the NHDOT Parcel Mosaic Viewer confirms which Coos County parcel you're looking at. Laying the county parcel outline beside the FEMA shading lists whether a homesite near Dalton sits above or inside the zone.
Step one: the free Coos County viewer
For Coos County, the free public parcel layer is state-run: open the NHDOT Parcel Mosaic Viewer and pan to Colebrook. Expect a disclaimer screen the first time you open the Coos County map; accept it and the parcels load. Click any Coos County parcel near Columbia to open its record: owner, parcel ID and assessed acreage are typically listed. Bookmark our Coos County page too; it tracks the official New Hampshire link if it moves and lists the maps around Columbia.
What the flood zone letters mean
On the FIRM covering Coos County, zones that start with A or V are Special Flood Hazard Areas, meaning FEMA estimates a 1-percent annual chance of flooding. Zone AE near Dalton means FEMA published a base flood elevation; plain Zone A means no detailed elevation was studied. If a Coos County parcel lists shaded Zone X, it is moderate risk, between the 1-percent and 0.2-percent annual chance lines. Unshaded Zone X near Dalton is minimal risk.
Tracts that cross the Coos County line
A farm near the county line can carry separate records in Oxford County, ME, Carroll County, and Grafton County as well. Every map bordering Coos County is listed on our New Hampshire directory.
Low ground and small streams around Berlin
A low spot on a Coos County tract outside any mapped zone, which is why it is worth walking the ground after a heavy rain.
Towns and land across Coos County
From Lancaster, the seat of the county, the map spreads out to Berlin, Carroll, Clarksville, and Colebrook. Unincorporated communities in the county, including Gorham, Groveton, and West Stewartstown, display up as small groups of parcels along the roads. Coos County had an estimated 31,372 people in 2023 (Census Bureau), spread across about 1,795 square miles. Beyond the town lots in Clarksville, expect big rural parcels across the county.
Flood insurance and building rules in Coos County
Insurance is the practical stake for a Coos County buyer. Where a building in Berlin falls inside an A or V zone and is financed by a regulated or federally insured lender, a flood policy becomes a loan condition, provided the community near Berlin takes part in the National Flood Insurance Program. For a county home in shaded or unshaded X, coverage is optional; pricing a policy for land near Dalton is still worth a call. When a Coos County homesite is on a rise inside a mapped zone, FEMA's LOMA process allows a review, typically backed by an elevation certificate from a surveyor who works in Coos County. Placing fill on low ground near Berlin typically needs a floodplain permit, and the building office serving Dalton explains the steps.
Where Coos County land records are kept
The parcel layer for Coos County points back to recorded deeds and plats, kept by the county's recording office (its title varies by state). Easements and access rights near Columbia live in recorded documents, so read the deed, not just the county map.
Coos County, NH: common questions
What is a base flood elevation for a Coos County property?
For a Coos County property in Zone AE, it is the projected water surface in the base flood, and it is printed in AE zones.
What does 100-year flood mean for Coos County land?
Not at all; a Coos County tract in that zone faces a 1-percent annual chance, so floods can come in back-to-back years.
Can I build in a flood zone in Coos County?
Often, but local floodplain rules apply; ask the county or town building office in Lancaster before you buy.
Do I need flood insurance in Zone X in Coos County?
FEMA doesn't require it for a Zone X lot in Lancaster, but coverage is available and some lenders ask for it.
Is there a floodplain layer in the NHDOT Parcel Mosaic Viewer?
Check the layer list in the NHDOT Parcel Mosaic Viewer; if Coos County includes a floodplain layer, confirm the zone on FEMA's map anyway.
Is my Lancaster address in a flood zone?
Look it up at FEMA's Flood Map Service Center, then match the parcel lines in the NHDOT Parcel Mosaic Viewer; for land near Clarksville, a zone starting with A or V is high risk.
Open the official Coos County, NH parcel map Coos County in the Platbookmapper directory
Not a survey. County GIS and tax parcel maps are assessment and planning layers. They are not a substitute for a recorded plat, deed, or licensed survey, especially for fences, setbacks, or boundary disputes.