The Impact of Levee Openings on Storm Surge: A Numerical Analysis in Coastal Louisiana

The existence of the Mississippi River (MR) and Tributaries' levees in coastal Louisiana could block storm surge and cause surge setup in adjacent basins. In order to reduce storm surge amplification caused by these barriers, one possible solution is to build floodways through the mainstem MR levees to allow surge during tropical events to cross. The primary purpose of this study is to examine if these floodways/openings can help reduce storm surge in adjacent basins. Using Hurricane Isaac (2012) as an example, a pre-validated Delft3D-based hydrodynamic model was applied to study the effect of levee openings on storm surge. Model results and flux analysis show that these levee openings were not effective in reducing storm surge in Barataria Basin and Breton Sound due to the complex interaction between the cross flow from the surge and the MR flow. During Isaac, the MR water could be diverted to Barataria and/or Breton, which resulted in an increase in storm surge, essentially defeating the primary objective of the levee openings. Overall, the impact of levee openings at the selected locations on storm surge reduction in adjacent basins of coastal Louisiana was minor and very limited.

Automated summary

The study found that levee openings in coastal Louisiana have limited impact on reducing storm surge in adjacent basins, mainly due to complex interactions between the surge and the flow of the Mississippi River. The openings were not effective in reducing storm surge during Hurricane Isaac due to diversion of river water into adjacent basins, essentially defeating their intended purpose.