Sullivan County, TN Environmental Rules: Stormwater Management (2026)

Article 8-103 of the Sullivan County Zoning Resolution, Peak Stormwater Management and Erosion and Sediment Control Pollution Prevention, governs drainage in the unincorporated county to protect residents from flooding, excessive runoff and sedimentation of the county's streams, creeks, sinkholes and lakes. 10 whether a stormwater management plan is needed based on historical data, floodplain studies and hydrologic calculations; where required, the plan goes to both the Highway and Planning and Codes Departments for review before the Commission acts on it. Structural improvements must hold post-development runoff at or below predevelopment levels for the 2-year and 10-year storm events, and the Commission can demand protection up to the 25-, 50- or 100-year storm where a known downstream flooding problem exists.

A December 2024 amendment added a state-driven design standard: stormwater control measures must achieve at least 80% removal of total suspended solids from the water quality treatment volume generated by a 1-year, 24-hour storm, with uncontaminated roof runoff excluded. Where runoff is channeled onto adjoining land, the developer must record a drainage easement so affected neighbors are on notice. Larger or higher-density projects, and any land disturbance of an acre or more, require Planning Commission or Building Commissioner sign-off on the grading plan before a grading permit issues, and a pre-construction meeting is mandatory for projects draining into an impaired stream or Exceptional Water of the State.