Harrison County, MS Environmental Rules: Stormwater Management (2026)

Adopted as UDC § 1012, the Drainage Management Site Plan Ordinance applies only to the unincorporated area of Harrison County: it supplements, rather than replaces, the county's separate Subdivision and Zoning Regulations, and it does not reach Gulfport, Biloxi, Long Beach, Pass Christian or D'Iberville, which administer their own drainage rules. A Drainage Management Site Plan (DMSP), sealed by a Mississippi-registered professional engineer, must model runoff for the 25-year, 24-hour storm and demonstrate that the controlled release rate from the site will not exceed the pre-development rate unless no significant downstream harm results.

Detention basins, culverts and channel sections must be sized against that standard, and an excess stormwater passage capable of carrying a 100-year, 24-hour event must be provided through every site, with no buildings permitted inside it. 02. 03 sets no fee for submitting the DMSP itself, though a separate, refundable Utility Permit fee applies to right-of-way encroachment work. Maintenance of stormwater improvements must be secured through a recorded maintenance agreement or covenant running with the property.