Decatur, AL Hurricane Preparedness: Flood Elevation (2026)

Decatur's floodplain ordinance covers two situations where no simple base flood elevation is printed. In approximate A-zone streams, where the map shows a stream but no base flood data, new construction and substantial improvements must have the lowest floor, including the lowest enclosed area and basement, elevated no less than three feet above the highest adjacent grade. Because the standard elsewhere calls for one foot above the BFE, the code states the structure must in this case sit no less than four feet above the highest adjacent grade. Before that fallback applies, § 25-32(d)2 has the floodplain administrator obtain and use any scientific or historic BFE and floodway data from a federal, state or other source. New subdivisions and developments over 50 lots or five acres, whichever is less, must supply BFE data.

In AO zones, where base flood depths run one to three feet above ground with no clearly defined channel, the lowest floor must be elevated above the highest adjacent grade at least as high as the depth number on the FIRM plus one foot of freeboard. If the map carries no depth number, the floor must be at least three feet above the highest adjacent grade. Non-residential buildings can be floodproofed in lieu of elevation to that level with an engineer's or architect's certification, and drainage paths must guide floodwater around and away from the structure.

Manufactured homes without a BFE must have the chassis supported no less than 36 inches and up to a maximum of 60 inches above the highest adjacent grade, with utilities at least three feet above grade. The floodplain administrator certifies the lowest floor elevation and the record becomes a permanent part of the permit file.