Nassau County, FL Environmental Rules: Flood Elevation Requirements (2026)

8 of Article 10 sets Nassau County's freeboard and grading standards. 1 requires the finished floor of any structure built in a Special Flood Hazard Area to sit at least one foot above the current 100-year flood level, and that elevation controls no matter what else the drainage plan shows. 2 covers everything outside a flood hazard area: the floor must match the elevation in the engineer of record's county-approved drainage plan. 3 sets a floor of at least 18 inches above the centerline elevation of the adjacent roadway, though lots larger than one acre can go lower with Engineering Services' approval.

4 caps the maximum finished floor elevation at six inches above what the approved drainage plan specifies, again with a break for lots over an acre. 6 requires Engineering Services to inspect the completed site grading and confirm in writing that the work matches the permit, and the Board of County Commissioners sets the inspection fee by resolution. 7 requires a separate lot grading plan, showing existing and proposed conditions, whenever fill will be placed more than five feet outside the building foundation or within ten feet of a property line, including fill under a raised septic system.

9 lets Engineering Services require retaining walls, roof gutters, underdrains or swales on top of these elevation rules whenever they are needed for adequate drainage.