Bayou Dupont Ridge Creation and Marsh Restoration (BA-48)

Problems: There is widespread historic and continued rapid land loss within the project site and surrounding areas resulting from subsidence, wind erosion, storms, and altered hydrology. Land loss data provided by the U.S. Geological Survey indicates that loss was occurring at a rate of 1.7% per year prior to construction. The natural limits of Bayou Dupont were difficult to determine in some areas because land loss was causing a merge of the bayou to adjacent water bodies. Natural tidal flow and drainage of patterns that once existed through the bayou were circumvented by the increasing area of open water.

Restoration Strategy: Project goals included: 1) creating and nourishing approximately 390 acres of marsh through sediment pipeline delivery from the Mississippi River; and   2) creating over two miles of ridge (10.5 acres of ridge habitat) along a portion of the southwestern shoreline of Bayou Dupont. Sediment from the river was hydraulically pumped to the project site to construct both the marsh and ridge features and additional material was dredged from Bayou Dupont to cover the ridge. The ridge is designed to mimic the configuration of other natural ridges within the watershed, and includes a constructed elevation conducive for the growth of native vegetation such as live oak, hackberry, and yaupon. The ridge is helping to redefine the limits of Bayou Dupont and reestablish the natural bank that once flanked the bayou and  protected adjacent marshes.

Location: This project is located within the Barataria Basin in Jefferson and Plaquemines Parishes. The marsh creation area is located along Bayou Dupont southeast of the waterbody known as the Pen.

Progress to Date: Construction began in the Fall of 2014 in conjunction with the Mississippi River Long Distance Sediment Pipeline Project (BA-43EB) and Bayou Dupont Sediment Delivery-Marsh Creation #3 (BA-164). Construction of the Bayou Dupont (BA-48) portion was completed in fall of 2015.

This project is on Priority Project List 17.

• Federal Sponsor: National Marine Fisheries Service (NOAA)
• Local Sponsor: Coastal Protection and Restoration Authority (CPRA)

Bayou LaLoutre Ridge Restoration and Marsh Creation

Historic and current ridge habitat loss occurs in the form of subsidence and shoreline erosion along Bayou La Loutre. The shoreline erosion is caused by increased boat traffic diverted due to the closure of the MRGO channel. Ridge habitat consists of Live Oak Hackberry Maritime forest which is utilized by trans-gulf migratory bird species as a first and last stop when crossing the Gulf of Mexico. This critical habitat is rated as S1-Most Critically Imperiled (State Natural Heritage Program) and S2 priority by the state of Louisiana. Interior marsh loss along Lena Lagoon is caused by subsidence, sediment deprivation, increased wave fetch and construction of access and navigational canals. The integrity of the Lena Lagoon shoreline has been breached, and loss of this wetland buffer will expose the La Loutre ridge to highly erosional winter storm events.

The goal of the project is to create an approximately 31.7 acre ridge feature with material from bucket dredging Bayou La Loutre. Additionally dredged material from Lake Borgne will create 163 acres of marsh and nourish approximately 258 acres of marsh along Lena Lagoon (421 acres total).

The proposed project will create approximately 5.46 miles (28,855 ft) of ridge along Bayou La Loutre and 24.4 acres of Live Oak/Hackberry Maritime forest habitat. The ridge habitat will be built centerline along the bank of the bayou. The structure will have a +4 elevation with a 5:1 slope on the bayou side and 3:1 slope on the marsh side. Additionally the newly created ridge will include herbaceous and woody plantings with smooth cord plantings along the toe. The Lena Lagoon site will create and nourish approximately 421 acres of marsh using sediment dredged from Lake Borgne. Lena Lagoon will have a semi-confined south and east flank and a fully confined north flank. Containment will be degraded as necessary to re-establish hydrologic connectivity with adjacent wetlands.

This project is located in Region 1, Lake Pontchartrain Basin and Breton Basin, St. Bernard Parish.

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

The Bayou LaLoutre Ridge Restoration and Marsh Creation project sponsors include:

• Federal Sponsor: National Resources Conservation Service
• Local Sponsor: Coastal Protection and Restoration Authority

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

 

 

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.

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.