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

Hamilton County defines the flood protection grade (FPG) as the base flood elevation (BFE) plus two feet of freeboard, a safety margin meant to cover uncertainty in flood modeling. For new construction or substantial improvement of a residential structure or manufactured home in a special flood hazard area (SFHA), the lowest floor, including any basement, must sit at or above the FPG. Non-residential structures get an alternative: they can be dry flood-proofed to the FPG instead of elevated, but only if an Indiana-registered professional engineer or architect certifies the structure and its utilities are watertight and can resist flood forces, pressures, and debris impact, and the floodproofing works without human intervention or outside power.

Where solid foundation walls elevate a structure, the walls need at least two flood-vent openings per enclosed wall, sized to one square inch of opening per square foot of enclosed area, with the bottom no higher than one foot above grade, so floodwater can enter and exit and equalize pressure automatically. The Hamilton County Plan Commission Director serves as floodplain administrator, reviewing permit applications, verifying as-built lowest-floor elevation certifications submitted by a registered surveyor or engineer before framing continues, and keeping those records on file for FEMA and DNR.