Charleston County, SC Environmental Rules: Flood Zones (2026)

Chapter 9, Article III applies this ordinance to all areas of special flood hazard within Charleston County's jurisdiction (Sec. 9-20). Under Sec. gov. The section is explicit that building inspection services will only issue permits based on the current effective FIRM or an authorized letter of map change, so a lot's flood-zone designation on the day of application controls the review. Sec. 9-31 lists what the building official must review before authorizing construction: a complete set of scaled plans showing exterior wall elevations, floor plans, foundation and wall sections, plus the base and design flood elevations and confirmation that materials below the design flood elevation are flood-resistant.

Floodways get the strictest treatment: Sec. 9-43(a) prohibits any encroachment, including fill, new construction or substantial improvement, within an adopted regulatory floodway unless a South Carolina-licensed engineer certifies through hydrologic and hydraulic analysis that the work will not raise flood levels during the base flood discharge. Subdivision applicants face parallel duties under Sec. 9-44: proposals must minimize flood damage, route utilities to avoid flood exposure, and supply base flood elevation data, generating it through engineering analysis where FEMA has not already mapped it. A denied applicant can appeal to the county construction board of adjustment and appeals under Sec.

9-50, but the written request must reach the building official's office within 30 calendar days of the decision, and a variance cannot issue if it would raise flood levels within the designated floodway.