Bayou Decade Ridge and Marsh Creation

The Terrebonne Basin is an abandoned delta complex, characterized by a thick section of unconsolidated sediments that are undergoing dewatering and compaction, contributing to high subsidence, and a network of old distributary ridges extending southward from Houma. Historically, subsidence and numerous oil and gas canals and pipelines in the area have contributed significantly to wetland losses. Since 1932, the Terrebonne Basin has lost approximately 20% of its wetlands. Current loss rates range from approximately 4,500 to 6,500 acres/year. This loss amounts to about130,000 acres over the next 20 years. One-third of the Terrebonne Basin’s remaining wetlands would be lost to open water by the year 2040. The wetland loss rate in the area is -0.79%/year based on USGS data from 1984 to 2016.

The proposed project’s primary feature is to create and/
or nourish approximately 504 acres of intermediate marsh adjacent to Lake De Cade and restore 11,726 linear feet of ridge habitat along the northern bank of Bayou De Cade. To achieve this, sediment will be hydraulically pumped from a borrow source in Lake De Cade. The borrow area in Lake De Cade would be located and designed in a manner to avoid and minimize environmental impacts (e.g., to submerged aquatic vegetation and water quality) to the maximum extent practicable. Containment dikes will be constructed around the marsh creation area to retain sediment during pumping. No later than three years post construction, the containment dikes will be degraded and/or gapped. Additionally, the newly constructed marsh will be planted after construction to stabilize the platform and reduce time for full vegetation. It is anticipated that material for the ridge feature will be mechanically dredged from adjacent areas within Bayou De Cade and/or the marsh area and lifted to a crown elevation of +5.0 feet, 25 feet wide, and will be planted.

This project is located in Region 3, Terrebonne Basin, Terrebonne Parish, Lake Mechant Mapping Unit.

This project was approved for Phase I Engineering and Design in January 2017 and is on Priority Project List (PPL) 26.

The Bayou Decade Ridge and Marsh Creation project sponsors include:

• Federal Sponsor: National Marine Fisheries Service
• Local Sponsor: Coastal Protection and Restoration Authority

Keep up with this project and other CWPPRA projects on the project page.

Wetland Plants

Plants are a vital piece of healthy and sustainable wetland ecosystems. Plants are the base of the food chain and can build new layers of organic material on top of wetlands which helps them keep pace with subsidence and rising waters. Wetland vegetation reduces erosion primarily by dampening and absorbing wave and current energy and by binding and stabilizing the soil with roots. Coastal wetland plant species are indicators of soil and hydrologic conditions. The amount and salinity of water in an area influence which plants grow there. Scientists often classify Louisiana marshes into four types: fresh, intermediate, brackish, and saline.

The Coastal Wetlands Planning, Protection, and Restoration Act puts native wetland plant benefits to use through restoration techniques that include vegetative plantings. Vegetative planting projects are used both alone and in conjunction with barrier island restoration, marsh creation, shoreline protection, and sediment and nutrient trapping restoration techniques. These projects use flood-and salt-tolerant native marsh plants that will hold sediments together and stabilize the soil with their roots as they become established in a new area.

BA-38 Barataria Barrier Island Complex Project: Pelican Island and Pass La Mer to Chaland Pass Restoration

 

 

 

 

Invasive species

National Invasive Species Awareness Week

Invasive species (harmful non-native species) are one of the most significant drivers of global change. Consequently, they can have substantial impacts on the economy, infrastructure, and humans. Society must address invasive species as a priority, which is exactly what National Invasive Species Awareness Week intends to do. The objective of National Invasive Species Awareness Week is to bring attention to the impacts, prevention, and management of invasive species – and all those who are working toward healthy, biodiverse ecosystems.

Wetlands provide benefits ranging from water filtration to storm surge protection; however, wetlands have become vulnerable to invasive species. Known as major contributors to wetland and coastal habitat loss, invasive species also threaten native species, including endangered species that rely exclusively on the wetlands for survival. The foreign animals that have been recognized as invasive to coastal wetlands include Asian carp, wild boar, island apple snails, and nutria. Invasive plant species include Chinese tallow, common reed, and purple loosestrife. Invasive animal and plant species have altered the health of wetlands by out-competing native species for food and natural resources, often without any natural predator or control to halt the resulting aggressive spread through an area. CWPPRA strives to protect wetlands by constructing methods to diminish the invasive threat and restore native species’ dominance and health within the wetlands.

For a full list of Invasive species in Louisiana, click here.

CWPPRA continues to raise awareness and identify solutions to protect our wetlands by implementing projects to target invasive wetland species such as the Coastwide Nutria Control Program and Louisiana Salvinia Weevil Propagation Facility.

 

 

Bayou Grande Cheniere Marsh & Ridge Restoration

Significant marsh loss has occurred south of Lake Hermitage with the construction of numerous oil and gas canals, subsidence, and sediment deprivation. The most significant loss occurred during the 1960s and 1970s. Based on the hyper-temporal analysis conducted by USGS for the extended boundary, loss rates in the project area are estimated to be -1.16% per ear for the period 1984 to 2011.

The goals of the Bayou Grande Cheniere Marsh and Ridge Restoration Project (BA-173) are to restore marsh habitat adjacent to the eastern shoreline of Bayou Grande Cheniere, reestablish the corresponding section of the bayou’s forested ridge habitat along this shoreline, and create terraces to restore marsh in open water habitat. Specific objectives are to 1) restore 302 acres of brackish marsh habitat, 2) construct the marsh platform to an elevation that supports healthy marsh; 3) reestablish 10,625 linear feet of the historic Bayou Grande Cheniere Ridge to an elevation that supports healthy woody vegetation, 4) establish the ridge with diverse native woody species, and 5) construct 12,000 linear feet of terraces to an elevation that will support healthy marsh.

Riverine sediments will be hydraulically dredged and pumped via pipeline to create/nourish approximately 302 acres of marsh. Containment dikes will be constructed around the perimeter of the marsh creation cells. The proposed design is to place the dredged material to a target fill elevation of +3.0 feet which would ultimately settle to an approximate elevation of just under +0.75 feet NAVD88 (Geoid 12A) at TY20. Tidal creeks are expected to form naturally and containment dikes will be gapped and degraded to enhance the naturally formed tidal creeks.

Hydraulically dredged river sediments will be used to restore 10,625 linear feet of the Bayou Grande Cheniere Ridge. The ridge will have 25-ft crown width, a target height of +4.5 ft NAVD88, and side slopes of 1(V):8(H). Herbaceous plantings (e.g., seashore paspalum) will be necessary immediately after construction and bottomland hardwood species (seedlings and saplings) will be planted by Year 3. Funding for tallow control and maintenance plantings is also included.

In addition, 11,700 linear feet of earthen terraces will be constructed resulting in the creation of approximately 10 acres of wetlands benefiting 154 acres of open water. Each terrace segment will be approximately 450 feet long and built to an elevation of +3.0 feet, with a 25-foot crown width and 1(V):4(H) side slopes. The terraces will be constructed with a bucket dredge using in situ material from within the terrace field.

This project is located in Plaquemines Parish west of the Mississippi River near West Pointe a la Hache. Specifically, the project features are south of Lake Hermitage and along the eastern side of Bayou Grande Cheniere.

This project is on Priority Project List (PPL) 23.

The Bayou Grande Cheniere Marsh & Ridge Restoration project sponsors include:

• Federal Sponsor: U.S. Fish and Wildlife Service
• Local Sponsor: Coastal Protection and Restoration Authority 

Keep up with this project and other CWPPRA projects on the project page.