Mobile, AL Environmental Rules: Flood Elevation Requirements (2026)

In special flood hazard areas without base flood elevation data, new construction and substantial improvements of existing structures shall have the lowest floor (for the lowest enclosed area; including basement) elevated no less than three (3) feet above the highest adjacent grade.(12)In the absence of a base flood elevation, a manufactured home must also meet the elevation requirements of section 17-27(7)b. in that the structure must be elevated to a maximum of sixty (60) inches (five (5) feet).(13)Openings sufficient to facilitate automatic equalization of flood water hydrostatic forces on exterior walls shall be provided in accordance with standards of section 17-27(5). The city engineer shall certify the lowest floor elevation level and the record shall become a permanent part of the permit file.(14)Fill within the area of special flood hazard shall result in no net loss of natural floodplain storage. The volume of loss of floodwater storage due to filling in the special flood hazard area shall be offset by providing an equal volume of flood storage by excavation or other compensatory measures at or adjacent to the development site. Any excavation or other measures taken for compensatory storage shall be properly designed to provide protection against erosion or overgrowth of vegetation in order to preserve the storage volume. Proper maintenance measures shall also be undertaken to ensure the intended storage volume remains in perpetuity.