Hudson, NH Environmental Rules: Flood Elevation Requirements (2026)

Any proposed development within a special flood hazard area of Hudson needs a floodplain permit issued by the Town Engineer under § 218-3, on top of the ordinary building permit the Building Inspector reviews under § 218-5 to confirm the site will be reasonably safe from flooding. Where FEMA's Flood Insurance Study already maps a base flood elevation for Zone AE, the Town Engineer uses that figure; in Zone A, where no official number exists, the Building Inspector must first check any federal, state or local source, including data submitted with a subdivision or site plan application, before falling back to the default of two feet above the highest adjacent grade under § 218-4D.

Residential structures must then have their lowest floor, including any basement, built at or above that base flood elevation under § 218-4E(1). A nonresidential building can instead be floodproofed watertight below the base flood elevation, with structural components built to resist hydrostatic and hydrodynamic loads, certified by a licensed engineer or architect. Manufactured homes must sit on a permanent foundation at or above the base flood level and be anchored against flotation and lateral movement. Any enclosed area below the lowest floor must be unfinished, used only for parking, access or storage, and vented with at least one square inch of flood-opening area per square foot of enclosed space, with openings no higher than a foot above grade.

A structure missing the elevation certificate or other documentation FEMA regulations require is presumed to be in violation until it's produced. Appeals and variance requests go to the Joint Committee of the Zoning Board of Adjustment and the Building Board of Appeals under § 218-8, which can only grant relief on a showing of hardship and undiminished flood risk to others.