Hammond, IN Environmental Rules: Flood Elevation Requirements (2026)

02's definitions establish the mechanics behind Hammond's elevation standard. BASE FLOOD ELEVATION (BFE) is defined as the water surface elevation of the base flood relative to a specified datum, usually the North American Vertical Datum of 1988. FLOOD PROTECTION GRADE (FPG) is then defined as the BFE plus 2 feet at any given location in the SFHA, with the same definition cross-referencing FREEBOARD, defined as a factor of safety, usually expressed in feet above the BFE, applied to compensate for unknown factors that could push flood heights above the calculated base flood.

For Zone AO sites, the BFE is instead equivalent to the flood depth on the FIRM measured from the highest adjacent grade, defaulting to 2 feet if no depth is specified. 42(B) applies that 2-foot freeboard standard operationally: in Zone A and Zone AE, new construction or substantial improvement of any residential structure must have its lowest floor, including any basement, at or above the FPG; in Zone AH the same lowest-floor-at-FPG standard applies, with drainage paths required around structures on slopes; in Zone AO the lowest floor must be elevated 2 feet above the flood depth shown on the FIRM (or 2 feet above the highest adjacent grade if no depth is specified).

42(B)(5) requires flood openings sized to at least 1 square inch of net area per square foot of enclosed area, on at least two different exterior walls, with the bottom of each opening no more than 1 foot above grade.