Design flood elevation

The design flood elevation is the height flood-resistant construction is designed to: the base flood elevation plus the freeboard the building code requires for the structure's category. It is the operative number on drawings — lowest floors, flood-proofing, and critical equipment are placed against the DFE, not the bare BFE.

The BFE/DFE distinction keeps two roles straight: the BFE is the map's modeled water surface; the DFE is the code's answer to it, deliberately higher. For existing-building analysis the DFE also frames retrofit questions — elevating equipment, wet- or dry-floodproofing — since compliance obligations attach when work in the flood zone crosses the substantial-improvement line.