Marietta, GA Environmental Rules: Stormwater Management (2026)

Article 7-8-14 applies to new development adding 5,000 square feet or more of impervious surface or disturbing one acre or more, to matching redevelopment thresholds, and to any hotspot commercial or industrial use regardless of size, per § 7-8-14-010(D). Design must follow the Georgia Stormwater Management Manual as directed by the public works director, who serves as administrator. 2-inch rainfall event, with runoff reduction mandatory for plans submitted after December 10, 2020. Subsection E requires stream channel protection through 24-hour extended detention of the one-year, 24-hour storm, erosion-prevention measures, and preservation of any applicable stream buffer.

Subsection F requires overbank flood protection controlling the post-development peak discharge rate for the 25-year, 24-hour storm to the pre-development rate, and subsection G requires the 100-year, 24-hour storm to not be exacerbated. A downstream peak-flow analysis under subsection H must extend to the point where the site represents 10 percent of the total drainage area. Every project must record an inspection and maintenance agreement binding the owner and future successors to keep the stormwater system functioning as designed.