Louisiana’s Defense Systems: Wetlands and the Case of the Great Wall of Louisiana

In 2013 the US Army Corps of Engineers (USACE) completed construction of the “Inner Harbor Navigation Canal Lake Borgne Surge Barrier”. The project is funded through the Hurricane and Storm Damage Risk Reduction System (HSDRRS) for southeast Louisiana and considered to be the largest civil works project in corps history. The barrier was built to combat storm surge heights like those observed during Hurricane Katrina in 2005. More commonly known as the Great Wall of Louisiana, engineering innovations like a 1000 foot trestle allowed the project to be completed in about 3 years’ time instead of an estimated 20. The barrier wall is 1.8 miles in distance, 26 feet tall, and at an estimated construction cost of $1.1 billion federally funded dollars.

Louisiana contains 40 percent of the continental United States’ wetland acreage. Coastal wetlands can protect against storm surge energy and flooding by marsh grasses, trees, and soil working as as system. However Louisiana continues to lose wetlands due to problems like subsidence, sea-level rise, sediment deprivation, oil and gas development, and climate change. With an extreme need of wetland preservation, coastal agencies like CWPPRA and USACE are strategizing to combat these issues.

USACE is one of the five managing agencies of the Coastal Wetlands Planning, Protection, and Restoration Act. CWPPRA’s mission is to fund, plan, design, and construct restoration projects in coastal Louisiana at a large and fast pace scale. CWPPRA projects are synergistically funded through partner programs, such as the Inner Harbor Navigation Canal Borgne Surge Barrier to protect, preserve, and restore Louisiana’s coast.

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Terrebonne Bay Marsh Creation-Nourishment

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Emergent marshes north of Terrebonne Bay have been
eroding as fast or faster than almost any other marshes
along coastal Louisiana. As these marshes convert to
shallow open water, the tidal prism will increase which will
in turn increase the frequency and duration of tides north
of Terrebonne Bay. This increasing tidal prism is likely
to increase the future interior marsh loss rates for those
marshes directly north of Terrebonne Bay. These marshes are
important for their habitat values as well as serving to slow
the progress of highly saline waters that threaten the lower
salinity marshes north and west of Madison Bay and in the
Lake Boudreaux basin. The
continued loss of these marshes has directly contributed to
the ongoing flooding problems of many communities along
Bayou Terrebonne including the town of Montegut.

The primary goal of this project is to fill shallow open water
areas and nourish marshes north of Terrebonne Bay/Lake
Barre thereby reducing the tidal prism north of Terrebonne
Bay and
interior land loss from tidal scouring. Specific Goals: 1)
Create 365 acres of intertidal marsh in shallow open water
and nourish 299 acres of fragmented marsh within the
project area reducing
water exchange between Terrebonne Bay and interior lakes
during tidal and small storm events. 2) Reduce erosion along
16,000 ft of the northern Terrebonne Bay shoreline.

The proposed features of this project consist of filling
approximately 365 acres of shallow open water and
nourishing approximately 299 acres of very low or
fragmented marsh with material hydraulically dredged from
Terrebonne Bay/Lake Barre. Containment dikes will be
degraded/gapped within 3 years of construction to allow
for greater tidal and estuarine organism access. This project
could be one part of a phased comprehensive plan to protect
the northern shoreline of Terrebonne Bay and the interior
marshes from further erosion and reduce the tidal prism.
The project would result in approximately 353 net acres of
marsh over the 20-year project life.

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This project is located in Region 3, Terrebonne Basin,
Terrebonne Parish, along the northern shoreline of Lake
Barre/Terrebonne Bay near Bayou Terrebonne continuing
east a short distance past Bayou Chitique.

This project is on Project Priority List (PPL) 20.

The Terrebonne Bay Marsh Creation-Nourishment project sponsors include:

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

 

CWPPRA

Are you aware of CWPPRA’s Programmatic Benefits?

  • Proven Track Record of Project Construction– Over 25 years, 210 approved projects benefiting more than 1,344 square miles (800,000 acres); 108 constructed (16 under construction).
  • Responsive– CWPPRA projects are constructed in 5 to 7 years.
  • Interagency Approach– Cost-effective projects developed by an experienced interagency team (5 Federal, 1 State agencies).
  • Community Involvement– Local governments and citizens contribute to project nominations and development.
  • Predictable Funding– Federal Sport Fish & Boating Safety Trust Fund funding to 2021 through fishing equipment taxes and small engine fuel taxes.
  • Fiscally Responsible– CWPPRA projects are cost-effective.
  • Science Based– CWPPRA’s monitoring program (Coastwide Referencing Monitoring System-CRMS). Demonstration projects “field-test” restoration techniques for future restoration project success.
  • Complementary– CWPPRA projects complement other large-scale restoration efforts (i.e., Coastal Impact Assistance Program, State Master Plan, BP DWH Oil Spill Early Restoration and the RESTORE Act).

CWPPRA has been and will continue to be the primary source of practical experience, learning, and agency expertise regarding coastal restoration in Louisiana.

 

CWPPRA

What are the strengths and the successes of CWPPRA?

  • Addresses the urgent need for on-the-ground coastal restoration in Louisiana
  • Constructs coastal restoration projects that protect critically impaired wetland areas
  • To date, has constructed 108 projects with a total of 152 active projects that will protect and restore approximately 100,000 acres of land
  • Has 25 years of experience in coastal restoration, acting as the State’s only consistent Federal restoration funding authority
  • Upon completion, projects provide benefits which meet local and state restoration planning goals
  • Initiated and supports the State’s only coastwide monitoring program to evaluate the efficacy of restoration projects on an ecosystem scale
  • Serves as the foundation for the development of restoration science and identification of project needs that have become the platform for other restoration funding programs

Visit the CWPPRA project page to learn more about successful projects in your area.

Cameron Meadows Marsh Creation and Terracing

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Significant marsh loss in the Cameron Meadows area is attributed to rapid fluid and gas extraction beginning in 1931, as well as Hurricane Rita and Ike. Rapid fluid and gas extraction resulted in a surface down warping along distinguished geologic fault lines. During the hurricanes of 2005 and 2008, the physical removal of the marsh coupled with subsequent low rainfall has resulted in the conversion of intermediate to brackish marsh to approximately 7,000 acres of open water. In addition to these losses, significant marsh loss has resulted from saltwater intrusion and hydrologic changes associated with storm damages.

The goal of the project is to restore approximately 400 acres of coastal marsh habitat and reduce the fetch by constructing approximately 12,150 linear feet of earthen terraces. Sediment will be hydraulically dredged from the Gulf of Mexico and pumped via pipeline to create approximately 380 acres of marsh (295 acres confined disposal and 85 acres unconfined disposal). Funds are included to plant approximately 180 acres. Approximately 12,150 linear feet of earthen terraces will be constructed in a sinusoidal layout to reduce fetch and wind-generated wave erosion. Terraces will be constructed to +3.0 feet NAVD88, 15 feet crown width, and planted. Terrace acreage will result in four acres of marsh above Mean Low Water.

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The Cameron Meadows Marsh Creation and Terracing project is located in Region 4, Calcasieu/Sabine Basin in Cameron Parish, approximately five miles northeast of Johnson Bayou and five miles north of the Gulf of Mexico.

This project is on Priority Project List (PPL) 22. The 30% Design Review meeting was completed July 2015 and the 95% Design Review was completed in October 2016. In January 2017, the CWPPRA Task Force approved CS-66 for Phase II Construction.

The Cameron Meadows Marsh Creation and Terracing project sponsors include:

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

CWPPRA Project Construction

Did you know:

CWPPRA projects are constructed within 5-7 years from initiating engineering and design.

CWPPRA projects are built in a series of phases. The first in the series of phases is Phase Zero which includes conceptual project development. Once a project is approved through the CWPPRA selection process, the project undergoes two subsequent phases to completion. Following the initial phase is Phase One where a combination of pre-construction data collection and engineering and design is incorporated. Lastly, Phase Two encompasses construction, project management, construction supervision and inspection,  and operations, maintenance, and monitoring or OM&M. CWPPRA serves as the foundation for the development of restoration science and identification of project needs that have become the platform for other restoration funding programs. Over 25 years, the Coastal Wetlands Planning, Protection, and Restoration Act has authorized 210 projects, benefiting approximately 100,000 acres.