Vanderburgh County, IN Environmental Rules: Flood Elevation Requirements (2026)

Chapter 18.04 defines the Flood Protection Grade (FPG) as the Base Flood Elevation (BFE) plus two feet of freeboard at any given location in the Special Flood Hazard Area (Section 18.04.020). That two-foot cushion drives the county's construction standards in Section 18.04.050(C)(2)(b): in Zone A and Zone AE, new construction or a substantial improvement of a residential structure must have its lowest floor, including any basement, at or above the FPG. Non-residential structures under Section 18.04.050(C)(3)(b) must either be elevated to the FPG the same way or floodproofed to that level by a Registered Professional Engineer or Architect who certifies the structure and its utilities are watertight and can resist hydrostatic and hydrodynamic flood forces.

If solid perimeter walls are used to elevate a structure, the enclosed area below the FPG must have engineered flood openings, at least two on different sides, sized to one square inch of net opening per square foot of enclosed area, per Section 18.04.050(C)(2)(c). Critical facilities such as schools, hospitals and emergency response installations must have their lowest floor elevated to or above the FPG under Section 18.04.050(E). Applicants must submit elevation plans in NAVD 88 at the application stage and, once the lowest floor is set, a surveyor- or engineer-certified Elevation Certificate to the Floodplain Administrator before construction proceeds further, per Section 18.04.040(B).