Depending on your address, the permit question goes either to the city's Permit Center, which reviews plans for new construction and alterations and issues building permits, or to Calcasieu Parish, which requires permits before any type of construction. Very little of the parish sits outside the 100 or 500-year flood plain, and the parish requires a permit before work starts in any Special Flood Hazard Area. Whether your wall needs a permit isn't something I'd guess at, so the Permit Center at 337-491-1294 is the place to ask which office covers your address. We check with that office before work starts, and when a permit's needed we handle the paperwork or walk you through it.
The ground is the other thing that changes a wall here. South Louisiana soils can cause foundations to settle, which is why the parish strongly recommends a geotechnical engineer for soils testing and a structural engineer or architect for foundation design. One state highway manual on wall design says a poured cantilever wall, the kind with a footing that reaches out under the soil, suits ground that carries weight well, and where the ground settles it may need piles or other foundation work, which raise the cost a lot. Around Lake Charles we usually see low, flat yards that hold water after a heavy rain, so I look at where your water goes before anything else. We work the same way in the cities around it, including Sulphur and Moss Bluff, and over the line in Orange, TX, and if your city isn't listed on the site, ask us.