Bay Raccourci Marsh Creation and Ridge Restoration (TE-156)

Post project degraded marsh and open water.

Location

The project is located in Region 3, Terrebonne Basin, Terrebonne Parish.

Problems

High saline waters from Lake Mechant have directly contributed to the loss and/or conversion of much of the historically intermediate marshes to low salinity brackish marshes north of Lake Mechant. Subsidence, canal dredging and storm damage have also contributed significantly to the loss of marsh in the area. The zone of intermediate marsh (transition zone between fresh and brackish marshes) is located just north of Lake Merchant. High salinity water entering Bay Raccourci via Bayou Raccourci/Lake Mechant flows unimpeded into low salinity marshes surrounding Bayou Raccourci, effectively short circuiting the TE-44 Project. The 1984 to 2016 USGS loss rate is -0.32%/yr for the extended boundary area.

Restoration Strategy

The primary goals of this project are; 1) restore marsh habitat in the open water and degraded marsh areas via marsh creation and 2) restore forested ridge habitat along Bayou Decade.

The project would consist of the creation of 341 acres if marsh and 103 acres of marsh nourishment with sediments dredged from Lake Mechant and confined with earthen dikes. The proposed design is to place the dredged material to a fill height of +1.17 ft NAVD88. Dewatering and compaction of dredged sediment should produce elevations conducive to the establishment of emergent marsh and within the intertidal range. Containment dikes will be gapped at the end of construction.

The northern containment dike would be built to a height of +4.0 feet NAVD88 with a 10 feet wide crown and would also serve as a ridge. Material for the ridge would be bucket dredged from both Bayou de Cade and from within the marsh creation cell. The entire 16,350 linear feet (17 acres) of ridge would be planted with saplings and bare root seedlings on the crown and smooth cordgrass along the bayou side slopes.

The project would result in approximately 342 net acres over the 20-year project life.

The project was approved for Phase I Engineering and Design in January 2020.

The project is on Priority Project List (PPL) 29.

The Federal Sponsor is US Fish & Wildlife Service.

The Local Sponsor is CPRA.

Phoenix Marsh Creation – East Increment (BS-42)

Degraded marsh in coastal Louisiana.

Location

The project is located in Region 2, Breton Basin, Plaquemines Parish.

Problems

Two major causes of wetland loss for this area are sediment deprivation and saltwater intrusion. Altered hydrology and oil/gas development have exacerbated this loss. Much of the fresh and intermediate marsh that once existed earlier in this century has either converted to more saline habitats or has become open water as a result of oil/gas canals, subsidence, and a lack of sediment deposition. The 1984 to 2019 USGS land change rate is -0.78% per year.

Restoration Strategy

The project goal is to restore 392 acres of marsh in the open water areas between Bayou la Croix and River aux Chênes through the placement of dredged material via hydraulic dredging. This project will work syngeristically with projects to the east by creating continuity with the Breton Landbridge Marsh Creation (West) Project (BS-38) and the Mid Breton Landbridge Marsh Creation and Terracing Project (BS-32). This proposed first increment would extend the reach of the Breton Landbridge and is part of an overall, long-range, restoration goal to create/nourish 1,000 to 2,000 acres of intermediate marsh across 5 miles of the Breton Sound Basin from River aux Chênes to the Mississippi River.

Sediment will be hydraulically dredged from the Mississippi River. The dredged riverine sediments will be pumped via pipeline into two semi-confined disposal areas. Where feasible, existing marsh will be used as containment instead of containment dikes.

Vegetative plantings are not proposed in the marsh creation areas, and containment dikes will be gapped no later than year three post construction.

Service goals include restoration/protection of habitat for threatened and endangered species and other at-risk species. This project would restore habitat potentially utilized by the black rail, which is proposed for listing as a threatened species. The project could also benefit other species of concern including the saltmarsh topminnow and seaside sparrow.

The project was approved for Phase I Engineering and Design in January 2020.

The project is on Priority Project List (PPL) 29.

The Federal Sponsor is US Fish & Wildlife Service.

The Local Sponsor is CPRA.