The Bayou Terrebonne Increment of the Terrebonne Basin Ridge and Marsh Creation Project is located in southeast Terrebonne Parish approximately 20 miles south-southeast of Houma. The project area has lost over half of its land to natural and human causes over the last 30 years.
This work, approved in the state’s Coastal Master Plan, is part of a larger effort to restore approximately 5,000 acres of ridge and marsh habitat in the Terrebonne Basin. Its goals align with CPRA’s mission to sustain coastal ecosystems that safeguard coastal communities and protect vital economic and cultural resources. Since Terrebonne Basin was damaged during the Deepwater Horizon oil spill, the engineering and design of the project have been funded through the Natural Resource Damage Assessment (NRDA) process.
- For more information on the NRDA process, view the final restoration plan here.
The project, as presented in the preliminary design, would restore approximately 10 miles of earthen ridge and up to 1,430 acres of marsh along the east bank of Bayou Terrebonne—about 2.3 square miles of ridge and marsh habitat in total. Early conversations with people who live, work, hunt, and fish in the project area influenced the design of both features.
Coastal ridge habitat supports woody species like trees and shrubs that need higher elevations to thrive. The current design of the project proposes to restore approximately 10 miles of ridge created by sediment deposits from the Mississippi River. The original ridge has eroded and subsided over time.
In most places, the current design locates the ridge along the east bank of Bayou Terrebonne to match its original location. When planning for the project began in 2018, local residents asked the project team to extend the project's boundary for ridge restoration past its initial endpoint near Bush Canal. In response to the request, the project team gathered data in the area and determined that it could be included in the project's design. To avoid existing homes and camps in the area and preserve their dock access to the bayou, the preliminary design shifts the new northern part of the ridge farther east to follow the edge of the marsh.
In its current state, the ridge has 11 openings that allow water to flow between Bayou Terrebonne and Lake Barre. Some of the breaks will need to be closed so the ridge can contain the material in the marsh creation areas on its eastern side. The current design proposes to close six of the existing breaks and leave the remaining five open for local navigation.
- Leave Open: 1, 3, 6, 8, 11
- Close: 2, 4, 5, 7, 9, 10
The current design would increase the height of the degraded ridge by approximately three to five feet in most locations and restore its width at the top to approximately 20 feet, creating a total of 64 acres of new ridge habitat.
The project’s original goal for ridge habitat creation was 126 acres. Further study revealed that a ridge wide enough to meet this goal would be difficult and costly to build, and it would have to push beyond the ridge’s original footprint into the adjoining marsh. To get closer to the original goal, the project team is considering a 60-foot-wide ridge in areas where the water is too deep to support new marsh creation.
To rebuild the ridge, the project will transport sediment from a borrow area in the bayou. A 25-foot buffer between the foot of the ridge and the edge of the borrow area will keep the ridge stable.
The preliminary design of the project also includes the restoration and creation of up to 1,430 acres of marsh beside the rebuilt ridge, which exceeds the project's original goal of 1,370 acres.
After local residents requested an expansion of the study area in 2018, the project team collected data in the original and new locations. They found that most of the original and expanded study areas have the right conditions to support marsh creation. Only three portions of the study area did not. For the most part, the water in those locations was too deep, making marsh creation too difficult and expensive to complete. These locations do not have marsh creation area markings around them in the map above.
The fill material for the marsh creation and restoration will likely come from nearby Lake Barre. Two proposed bay borrow areas, shown in the map below, were carefully selected for this project. The two areas avoid oil and gas wells and pipelines, have water deep enough for a dredging vessel, and minimize disturbances to natural habitat.
Once the marsh fill material has been dredged, temporary pipelines would transport it to the marsh creation areas. The proposed dredge pipeline corridors were selected to minimize environmental impacts and avoid existing oil and gas pipelines as much as possible. The dredge pipeline would float over oil and gas infrastructure when avoiding it is not possible.
The dredged material would be placed into the marsh creation areas contained by the newly restored ridge on the west and earthen containment dikes along their other boundaries.
Between June 24, 2020 and July 15, 2020, the project team encourages residents and stakeholders to review this online meeting and share their comments on the preliminary design. In the fall, the team plans to use the input to finalize the design of the project. Around the same time, CPRA will meet with private landowners to negotiate 25-year servitude agreements based on voluntary acquisition. These agreements will allow CPRA to construct and maintain the project on the owners' properties over the anticipated lifespan of the improvements.
If the permits are granted by summer 2021, construction should begin between late 2021 and early 2022. Depending on the intensity of its schedule, the construction process may take 20 to 36 months to complete. The construction will take place in phases, so no single ridge and marsh creation area will experience construction impacts for the entire period.