Doña Ana County, NM Environmental Rules: Flood Elevation Requirements (2026)

Under § 350-604 of the Doña Ana County Code, any development inside a FEMA-designated special flood hazard area (SFHA) shown on the county's Flood Insurance Rate Maps needs a floodplain development permit before work begins. Subsection H(1) sets the county's residential freeboard standard: new construction, substantial improvements, and reconstruction after substantial damage must have the lowest floor, including any basement, elevated to one foot above the base flood elevation (BFE), with a registered New Mexico land surveyor certifying compliance to the Floodplain Administrator. Nonresidential buildings under H(2) may instead be floodproofed watertight to the same one-foot-above-BFE line if a professional engineer or architect certifies the design.

The county layers on a three-stage elevation certificate process for new SFHA construction: a pre-construction certificate before the building permit is released, an under-construction certificate before the foundation is poured, and a post-construction certificate before a certificate of occupancy is issued, each signed and sealed by a licensed New Mexico surveyor and accepted by the Flood Commission. Manufactured homes placed in Zones A, AE, AH and AO must likewise have their lowest floor at or above the BFE and be anchored to resist flotation and lateral movement.

Enclosures below the lowest floor used for parking or storage need at least two flood-vent openings totaling one square inch per square foot of enclosed area, with the lowest opening no higher than one foot above grade. Recreational vehicles in the SFHA are exempt only if they stay under 180 consecutive days, remain licensed and highway-ready, or otherwise meet the elevation and anchoring standards. Because this is a county ordinance, it governs only the unincorporated area; Las Cruces, Sunland Park, Mesilla and Hatch administer their own floodplain codes.