Hurricane Protection
- St. Bernard Parish – Back Levee
St. Bernard Parish, Louisiana
the challengeSt. Bernard Parish is protected by two levee systems, a federal levee (Chalmette Loop Levee) and a non-federal levee (Back Levee). Both levee systems were damaged by Hurricane Katrina. The federal levee provides a continuous perimeter of protection around St. Bernard Parish, whereas the Back Levee is an inner levee that separates the inhabited areas from the adjacent bayous and marshlands. The Back Levee system is relatively environmentally uniform throughout its length. The St. Bernard Back Levee is owned, operated, and maintained by the Lake Borgne Basin Levee District (LBBLD). The LBBLD is also responsible for the eight pump stations, floodgates, control structures, canals, and a freshwater siphon within the St. Bernard Parish protected area. The project needed to evaluate the feasibility of various levee alignments, height, and subsequent estimated costs associated with construction of the alternatives for providing 100-year protection for the populated areas of St. Bernard Parish, without raising the federal levee.
the interdisciplinary approachThe US Army Corps of Engineers New Orleans District, Hurricane Protection Office contracted with the Bioengineering Group to evaluate alternatives which were developed for raising the protection to elevations 13.5’ and 17.0’, and to evaluate the possibility of incorporating the Back Levee into the overall federal levee protection system. The Bioengineering Group performed site reconnaissance field visits to become familiar with the existing structures and levees. This field work identified potential relocations, modifications to existing pumping stations and environmental impacts associated with the investigated design alternatives. The senior project design team conducted brainstorming techniques to determine the constructability and viability of each investigated alternative. The alternatives were evaluated for impacts to the levees, pump stations, floodgates, and floodwalls within the reaches to provide recommendations on the most feasible solutions to achieve level-one protection. A comparison of the recommendations and costs associated with modifications to the federal levee was created to determine the feasibility of incorporating the Back Levee into the overall federal levee protection system.
the resultsThe costs for incorporating the Back Levee system into the overall protection system compared favorably with those costs published in the draft PER for the federal-only option. Based on this, it was recommended that the Back Levee option proceed to the next planning/preliminary engineering phase. In addition, recommendations about the alternatives were made based on cost, schedule, real estate, environment, relocations, operations and maintenance, and level of uncertainty. The recommended plan to raise protection includes T-walls, levee raising, combinations thereof, and a floodgate at Violet Canal. Project costs for all alternatives include pump station upgrades and/or replacement.