Gretna, LA Environmental Rules: Stormwater Management (2026)

Section 10-15, "Lot grade rules and regulations," sets Gretna's local drainage standard on top of the state building code. Subsection (a)(3), Runoff, states that "the approved arrangements for handling direct run off (whether by retainer wall, approved sub-surface drainage, swale, or other approved alternative) shall be properly maintained by the property owner," putting ongoing maintenance squarely on the homeowner rather than the city. Where one lot sits higher than its neighbor, subsection (b) requires an approved arrangement to keep water from flowing directly onto the lower lot, and if the code official finds the elevation difference too great for a swale, a reinforced concrete or masonry retaining wall at least six inches thick is required on the rear and side property lines, extending two to six inches above the highest adjacent grade.

Retaining walls over 12 inches high, or that extend below the lower adjacent grade by less than their own height, must be designed and stamped by a design professional under subsection (b)(2). Subsection (e), Drainage servitude and facilities, addresses the case where new construction would sit higher than an existing rear-lot structure that drains to the rear: the builder must dedicate and record a drainage servitude on the new-construction lot and properly install drainage facilities there, and no certificate of occupancy or utility notification can issue until that servitude and those facilities are in place.

Lots 200 feet deep or more also require a design-professional-certified drainage plan filed with the building permit application under subsection (d), fully implemented before the final building inspection is scheduled.