New Bedford, MA Environmental Rules: Flood Elevation Requirements (2026)

Section 4440 splits New Bedford's base flood elevation and floodway rules into two parts. First, for Floodway Data: in Zones A and AE along watercourses that have not had a regulatory floodway officially designated, the City requires that the best available federal, state, local, or other floodway data be used to prohibit any encroachment that would cause an increase in flood levels within the community during a base flood discharge event. This means the absence of a mapped regulatory floodway does not exempt a project from floodway analysis; the City still applies the best data on hand to block any project that would raise flood elevations for neighboring properties.

Second, for Base Flood Elevation Data specifically: the ordinance requires base flood elevation data for subdivision proposals or other developments greater than 50 lots or 5 acres, whichever is the lesser threshold, when the project sits within an unnumbered A zone, meaning an area FEMA has mapped as a 100-year floodplain without establishing a specific base flood elevation number. Section 4480 builds on this by directing the building department to obtain, review, and reasonably use base flood elevation and floodway data from federal, state, or other sources as the basis for requiring new construction, substantial improvements, or other development in Zone A to elevate residential structures to or above base flood level, to floodproof or elevate nonresidential structures, and to prohibit floodway encroachments, even where FEMA has not itself supplied a BFE number for the site.

Section 4481 separately requires adequate drainage paths around structures on sloped ground within Zones AO and AH, to guide floodwaters around and away from the structure rather than through it.