Ouachita Parish, LA Environmental Rules: Flood Elevation Requirements (2026)

Sec. 21-117 sets the freeboard the parish adds on top of FEMA's 100-year base flood elevation. For any new residential or nonresidential structure, or the substantial improvement of one, in an unprotected area of special flood hazard, the lowest floor, including any basement, must sit at least one foot above the 100-year base flood elevation or at least one foot above the record inundation for that area, whichever is higher, and a registered professional engineer, architect or land surveyor must certify to the program administrator that the as-built lowest floor meets that mark.

Nonresidential buildings may floodproof to the same elevation instead of raising the structure, with the same engineer certification required. Where a levee or elevated flood-protection system is used to protect an area instead, Sec. 21-117(2) requires a minimum ten-foot top width, side slopes no steeper than three-to-one, and a crest at least three feet above the base flood elevation or the record inundation, whichever is higher. Subdivisions get a higher bar: Sec. 21-121(a)(2) withholds plat approval from the Police Jury unless the storm drainage and flood-control improvements protect the development to an elevation three feet or more above the base flood level, and Sec. 21-121(a)(3) additionally requires the internal drainage system to handle a 100-year design storm before the plat can record.