Coastal Protection and Restoration AuthorityRiver Reintroduction Into Maurepas Swamp | Coastal Protection And Restoration Authority

Background

Located directly west of Lake Pontchartrain, the Maurepas Swamp is a prime example of Louisiana’s iconic swamp habitat, providing a home to a wide range of wildlife species. As one of the largest forested wetlands in the United States, the Maurepas Swamp provides many recreational opportunities, including fishing, hunting, birding, kayaking, and more. The swamp also provides significant flood protection for the River Parishes and the Greater Baton Rouge area.

From the blockade of Bayou Manchac in 1814 to the construction of the Mississippi River levees in the early 20^th century, structures along the Mississippi River slowly cut the swamp off from the freshwater supply that provided it with nutrients, oxygen, and sediment. This hydrologic isolation of the swamp from the river has led to continuing swamp degradation, which has been exacerbated by past high salinity in the Pontchartrain Basin and destructive logging practices in the early 20^th century.

The River Reintroduction into Maurepas Swamp Project

The River Reintroduction into Maurepas Swamp project (MSP) will divert fresh water from the Mississippi River back into the swamp through a 5.5-mile controlled-flow diversion. The project will improve the health of the cypress-tupelo swamp through the addition of much-needed nutrients and the flushing of stagnant, low-oxygen water. Additional benefits are anticipated from the delivery of fine river sediment and from the ability to freshen the swamp if salinity rises to unhealthy levels for the trees.

The MSP will utilize a channel constructed to connect the Mississippi River to the Hope Canal. The channel will run near the Mt. Airy neighborhood and cross River Road and Airline Highway before connecting with Hope Canal in the Maurepas Swamp.

WSLP Integration

In January of 2023, the United States Army Corps of Engineers (USACE) formally selected the MSP as mitigation for the West Shore Lake Pontchartrain (WSLP) project. This decision marks the first time USACE has used a CPRA-led project as mitigation. Once complete, MSP and WSLP will share levee features and boundaries near Mt. Airy. This unique approach is a significant milestone in CPRA’s history and capitalizes on common features to maximize flood protection and restoration efforts for St. John the Baptist Parish.

The schematic below displays how the MSP will integrate with WSLP once complete. The cross-section, shown looking north, highlights the connection between the two projects and how they utilize shared features to advance flood protection and hydrologic restoration simultaneously.