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Stormwater Design Standards Manual

At a glance

The City of Charleston Stormwater Design Standards Manual sets the rules developers must meet for runoff, sea level rise allowances, special protection areas, Church Creek and wetlands. It was revised in 2020 and 2025, with a fee-only change in 2026; staff plan small yearly revisions and more incentives for low impact development.

Sources

Log

2026-11-05 - Charleston Basin Flood Action Committee

  • Director of Development Services Ron Bucci presented the manual to the committee. Designs must account for 5.5 ft NAVD 88 (sea level rise and surge) and dedicated roads must be at 7.5 ft; projects disturbing half an acre or more must control discharge rates and projects disturbing one acre or more must show no adverse impact in the 100-year storm.
  • In special protection areas, projects must cut flow rate and volume by 20 percent (15 percent with low impact development or city funding), with a simplified storage option and 1.1 to 1 credit for low impact development; smaller projects adding 500 square feet or more of impervious area must still add practices such as rain barrels or rain gardens.
  • Church Creek requires 100-year detention, case-by-case release rules and 1.25 to 1 fill displacement; basin improvement participation is encouraged over onsite storage.
  • Wetlands can be used only for conveyance, and a wetland scientist must document that a wetland will still function after development; the manual does not currently restrict wetland impacts. Charleston County is revising its own manual and is largely aligned with the city.
  • Bucci said few developers use the low impact development incentive so far, especially downtown; the sketch plan process lets staff suggest options early. Members asked about checking models against real storms; more downstream gauges are under consideration.