St. Tammany Parish Government Lake Pontchartrain Barrier Gate Modeling Project

The State of Louisiana’s Coastal Protection and Restoration Authority (CPRA) began investigating the potential flood damage reduction benefits—and possible adverse effects—of a proposed barrier across the mouth of Lake Pontchartrain as early as 2013. This work supported the development of the 2017 Coastal Master Plan. Initial evaluations were conducted using the Coastal Louisiana Risk Assessment (CLARA) model, which informed the Master Plan’s risk analysis. Atkinson and Roberts (2015) documented the preliminary design assessment and screening process, identifying a subset of viable barrier options, while Fischbach et al. (2017) provided further analysis to guide formal selection.

The early study evaluated twelve barrier alternatives and a future without action scenario. Variables included closure structure locations (e.g., U.S. 90 and CSX railway), gate heights (ranging from 0.6 to 6.0 meters), and barrier elevations (including options with no increase and a 3-meter elevation increase over U.S. 90). Leadon, Atkinson, and Fischbach (2018) later found that a barrier could impact water levels in nearby areas, including Lake Borgne and parts of western Hancock County, Mississippi.

Louisiana’s 2023 Coastal Master Plan formally includes the Lake Pontchartrain Barrier Project, described as the construction of closure gates and weirs to an elevation of 2 feet NAVD88 across Chef Menteur and the Rigolets, aimed at reducing storm surge risk in the Lake Pontchartrain Basin.

This project could reduce flood depths by up to three feet at year 50 in areas outside existing levee systems, such as coastal Slidell, parts of St. Tammany Parish, and the City of New Orleans. These reductions would protect approximately 5,800 additional residences and result in an estimated $680–$740 million in avoided losses. The barrier may also reduce the scope and cost of other future resilience projects in the basin.

Wingate Engineers, as a subconsultant to Stantec, provided critical technical support, including:

• Development of a Rough Order of Magnitude (ROM) cost estimate for structures at the Rigolets and Chef Menteur Passes;
• Quantifying and comparing changes in flooded structures and associated damages using preliminary inundation maps;
• Conducting cost-benefit comparisons between damage reduction values and the construction costs of the proposed structures.