Terracing

CWPPRA Restoration Technique: Terracing

The goal of building terraces is to achieve some of the same objectives as full marsh creation but over a larger area of open water, where marsh creation alone is not feasible. Terraces are long, earthen berms that are built by mechanically dredging material and piling and shaping the material to a desired height. Most terraces average around 3 feet tall, with shallow side slopes and a wide base. This size and shape optimize the amount of terrace that falls in the intertidal zone and will support wetland vegetation.

The objectives of constructing terraces are several and depend upon the location in which they are built. These include acting as a sediment trap to help build new land, reducing wave fetch and erosion on adjacent marsh shorelines, creating habitat for fish and waterfowl, and improving water quality to promote the growth of aquatic vegetation. Terracing projects constructed under CWPPRA have achieved each of these goals, with sediment trapping being most evident near the openings of sediment-laden bays or navigational waterways.

Terracing has become a widely used technique that is expanding across the Gulf Coast because of the success and cost-effectiveness demonstrated through CWPPRA and privately funded projects. Although these features may not look like natural marsh and often use geometric configurations, they are able to perform a lot of the functions of natural marsh in areas that have become vast open water. Developing this cost-effective technique for use in areas that have few other restoration options is a testament to CWPPRA’s ability to adapt to funding constraints and a quickly changing environment.

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TV-12 Little Vermilion Bay Sediment Trapping

 

 

 

 

Caminada Headlands Back Barrier Marsh Creation

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The Caminada Headland has experienced some of the highest shoreline retreat rates in Louisiana. Historically the shoreline has migrated landward at about 40 feet per year. Between 2006 and 2011, shoreline migration increased dramatically, exceeding 80 feet per year in near Bay Champagne and 110 feet per year in the Bayou Moreau area. The increased losses occurred in the wake of Hurricanes Katrina and Rita in 2005 as the breaches remained open for an extended length of time. The losses were exacerbated by Tropical Storm Fay and Hurricanes Gustav and Ike in 2008. Significant prolonged breaches greatly increase the net export of sediment from the headland.

In addition to the shoreline migration, the area is also experiencing high loss rates of interior marshes. As the beach and dune continue to migrate landward, overwashed sediment will be lost into newly formed open water and land loss rates will be exacerbated. The continued deterioration of Caminada Headland threatens thousands of acres of wetland habitat as well as critical infrastructure, including Port Fourchon, LA Highway 1, and the lower Lafourche levee system.

The goals of this project are to: 1) Create and/or nourish 385 acres of back barrier marsh, by pumping sediment from an offshore borrow site; 2) Create a platform upon which the beach and dune can migrate, reducing the likelihood of breaching, improving the longevity of the barrier shoreline, and protecting wetlands and infrastructure to the north and west. The proposed project is expected to slow the current trend of degradation in the headland.

This project would create 210 acres of back barrier intertidal marsh and nourish 175 acres of emergent marsh behind 3.5 miles of the Caminada beach using material dredged from the Gulf of Mexico. The marsh creation and nourishment cells are designed to minimize impacts on existing marsh and mangroves. Assuming some natural vegetative recruitment, vegetative plantings are planned at a 50% density, with half planned at project year one and half planned at project year 3. Containment dikes will be degraded or gapped by year three to allow access for estuarine organisms.

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The project area is defined as the area south of Louisiana Highway 1 between Belle Pass and Caminada Pass, directly behind Caminada Headland beach covering areas in and around Bay Champagne and areas east of Bayou Moreau. The Caminada Headlands Back Barrier Marsh Creation project is located along the Louisiana coastline in LaFourche Parish in CWPPRA Planning Region 2.

A kick-off meeting was held in June 2014. The project team has completed preliminary engineering and design, environmental compliance, real estate negotiations, operation & maintenance and monitoring planning, and a cultural resources investigation, all to the 95% design level as required by the CWPPRA standard operating procedures. The 30% design review meeting was held July 28, 2016 and the 95% design review was held on October 28, 2016. The Phase II Request for construction funding was presented to the CWPPRA Tech Committee on December 7, 2016.

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

The Caminada Headlands Back Barrier Marsh Creation project sponsors include:

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

Freshwater and Sediment Diversions

CWPPRA Restoration Technique: Freshwater and Sediment Diversions

The present location of the Mississippi River has been confined by levees constructed in response to the devastating flood of 1927. Although necessary for protecting life and property, the levees prevent the natural processes of delta building and sediment deposition that are vital for sustaining wetlands. Without this nourishment, the wetlands will eventually succumb to subsidence, storms, and anthropogenic impacts.

The CWPPRA program has been finding solutions to optimize river resources and help rebuild wetlands with minimal impact to other stakeholders. Controlled diversions route river water through strategic locations in the levees to feed starving marshes. Crevasses, or cuts, are constructed through levees to allow passive creation of smaller deltas. Siphons suction fresh river water and direct flow into wetlands suffering from saltwater intrusion. Water-control structures and channel maintenance help distribute river water diverted from large-scale structures constructed under other authorities.

The river presents the greatest opportunity for rebuilding land but also the greatest challenges, as competing needs are inevitable. The human and natural environments must be able to coexist because they are inextricably connected. Together with stakeholders, CWPPRA projects are helping to reverse land loss on an ecosystem scale and support the economy on which coastal Louisiana has come to depend.

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MR-03 West Bay Sediment Diversion

St. Catherine Island Marsh Creation & Shoreline Protection

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The landfall of Hurricane Katrina in southeast Louisiana destroyed thousands of acres of marsh and other coastal habitats in the Lake Pontchartrain basin. The hurricane weakened the Lake Pontchartrain shoreline and large areas of interior marsh habitat were either lost or damaged near Chef Menteur Pass. This area has an estimated erosion rate of 18 ft./yr. or greater. A portion of the lakeshore is protected by rock dikes (Bayou Chevee PO-22, State only project and FWS funded project). Shorelines that are not protected by rock dikes will erode back into the shallow open water areas located near the shorelines further increasing erosion rates.

This project would extend the Bayou Chevee (PO-22) rock dike along approximately 33,324 LF of weakened Lake Pontchartrain shoreline. A 6,468 LF foreshore dike and a 13,851 LF revetment totaling 20,319 LF is proposed to be built along a portion of the Bayou Savauge NWR. This would protect approximately 201 acres. This project would also create/nourish 115 acres (100 acres of marsh creation and 15 acres of marsh nourisment). That marsh would be created by filling those sites with material hydraulically dredged from the bottom of Lake Pontchartrain. A combination of healthy established marshes, bayou ridges, and constructed earthen dikes would contain that material. All constructed containment dikes would be sufficiently gapped within 3 years to allow for exchange of nutrients and estuarine organisms. This project would work synergistically with other restoration projects in the area including CWPPRA, state, and Bayou Savauge National Wildlife Refuge projects.

The goals of the project are to 1) stop shoreline erosion due
to wind generated waves along 33,324 linear feet of the Lake Pontchartrain shoreline, preserving 201 acres (166 acres of marsh and 35 acres of shallow water) and 2) create/nourish 115 acres (create 100 acres of marsh and nourish 15 acres of marsh) landward of that shoreline protection.

Service goals include the protection/creation of habitat or improvement of habitat for species of concern (LDWF), priority species (JV), and threatened and endangered species (FWS). The creation of low salinity brackish intertidal marsh habitat would be beneficial to several species that are currently on these lists, including, but not limited to Black Rail, Mottled Duck, Brown Pelican, King Rail, and Saltwater Topminnow. Helping to improve habitat, especially on Federal and State owned lands, ensures the protection of those valuable resources in perpetuity and should be a priority.

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This project is located in Region 1, Pontchartrain Basin, Orleans Parish.

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

The St. Catherine Island Marsh Creation & Shoreline Protection project sponsors include:

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

Barrier Island Restoration

CWPPRA Restoration Technique: Barrier Islands

Barrier islands are known as coastal Louisiana’s first line of defense against destructive storm surge. These islands are a unique composite of beach, dune, marsh, and sand flats that host a tremendous variety of fisheries and wildlife, including endangered species. Barrier island restoration projects are designed to protect and restore the features unique to Louisiana’s barrier island chains. This type of project may incorporate a variety of restoration techniques, such as the placement of dredged material to increase island height and width, the placement of structures to protect the island from erosive forces, and the placement of sand-trapping fences, used in conjunction with vegetative plantings, to build and stabilize sand dunes.

Responsible for the majority of Louisiana barrier island restorations to date, CWPPRA has led the charge in barrier island restoration because it recognizes the ecological importance of barrier islands and their critical role in the defense of coastal Louisiana.

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

 

Marsh Creation

CWPPRA Restoration Technique: Marsh Creation

Marsh creation replicates the natural land-building process of the Mississippi River in a controlled, and much accelerated, fashion. Land is built by a pipeline dredge that removes sediment from a “borrow” site by using a specialized vessel outfitted with a drill, suction pump, and pipe. As the drill, or cutterhead, spins, it agitates sediment at the bottom of the borrow site. This sediment is then pumped with water into a pipe that carries the resultant slurry to the restoration site. Once the slurry is in place, the water runs off as the sediment settles to form new land. Native vegetation is then installed to jump-start wetland productivity. Marsh creation projects result in restored wetlands in areas that were open water just weeks before.

CWPPRA is striving to identify and construct projects that provide strategic benefits by holding together larger ecosystems and that use renewable sediment resources like the river. Over the course of 26 years, CWPPRA has been restoring one piece of broken marsh at a time, which cumulatively yields significant results over time. The long-term vision is to sustain these restored marshes by restoring part of the riverine processes that first built them.

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PO-104 Bayou Bonfouca Marsh Creation Project

 

Bayou LaLoutre Ridge Restoration and Marsh Creation

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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.

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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:

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

 

 

Families Learn about the Importance of Wetlands

Families enjoying a Saturday adventure together on March 11th had the chance to explore different aspects of the ecosystems around them, including ways that wetlands help them and native wildlife. Coastal Wetlands Planning, Protection, and Restoration staff exhibited materials and games at the Estuarine Habitats and Coastal Fisheries Center as part of 2017 Family Adventure Day to benefit the non-profit Healing House in Lafayette, LA. This annual event sends families to different locations throughout Lafayette for experiences that range from face painting to coming face-to- face with a snake.

Over 250 people stopped by the Center where they had the opportunity to see a demonstration of how coastal wetlands protect interior communities and wildlife habitat from storm surge. Visitors could pick up recent issues of WaterMarks and other materials on wetlands restoration projects in coastal Louisiana. Kids also received Henri Heron’s activity book and helped match Louisiana wildlife with the wetland habitat they need to survive.

Other exhibitors, including US Fish & Wildlife Service and Louisiana Dept. of Wildlife & Fisheries, focused on topics like bat conservation, beekeeping, endangered species in Louisiana, and fishing. Helping families understand and appreciate the diversity of natural environments in Louisiana helps ensure that those environments will be present in the future.

Shoreline Protection

CWPPRA Restoration Technique: Shoreline Protection

Louisiana’s shorelines are eroding at a drastic pace, some at rates up to 50 feet per year. The fertile but fragile soils found in the wetlands are susceptible to wave energy. As land is lost, water bodies merge together, which can increase wave fetch and shoreline erosion. Behind these shorelines lie communities, highways, and infrastructure that are at risk of washing away.

Various techniques to defend the coastline have been tested and applied under CWPPRA. Rock revetments, oyster reefs, concrete panels, and other fabricated materials have been constructed along otherwise unstable shorelines to abate wave energy and reduce erosion. These structures are designed to break waves, and they often trap waterborne sediments behind the structures that, over time, can become new land.

Through the course of the CWPPRA program, advancements have been made in shoreline structures that have helped maintain natural processes while providing critical protection. Such advancements have included using lighter-weight materials that require less maintenance and can be constructed on organic sediments. Other advancements include low-relief structures that are designed to trap sediments and natural breakwaters such as reefs that can self-maintain and support other ecological functions. Other natural shoreline protection measures include vegetative plantings, whose roots help secure soils and can promote accretion. These projects are implemented with consideration for minimizing impacts to the surrounding environment. Although some shoreline structures may look foreign in a natural landscape, they are necessary features that physically protect communities and hold wetlands in place by mitigating the harsh forces that move to destroy them.

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BA-26 Barataria Bay Waterway East Side Shoreline Protection

 

Bayou Decade Ridge and Marsh Creation

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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.

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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:

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