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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Bayou Dupont Sediment Delivery – Marsh Creation and Terracing

Wetlands in the Barataria Basin were historically nourished
by the fresh water, sediment and nutrients delivered by
the Mississippi River and its many distributary channels.
These sediment and nutrient inputs ceased following the
creation of levees along the lower river for flood control and
navigation. In addition, the construction of numerous oil and
gas canals along with subsurface oil and gas withdrawal has
exacerbated wetland loss in the area. From 1932 to 1990, the
Barataria Basin lost over 245,000 acres of marsh. From 1978
to 1990, the area experienced the highest rate of wetland loss
in coastal Louisiana.

The primary goal of this project is to create and nourish
approximately 144 acres of emergent intermediate marsh
using sediment from the Mississippi River, and constructing
9,679 linear feet of terraces. The proposed project includes
dredging sediment from the Mississippi River for marsh
creation by pumping the sediment via pipeline into an area of
open water and broken marsh. The proximity of the project
to the Mississippi River provides a prime opportunity to
utilize this renewable river sediment resource. The strategy
includes utilizing the access route and infrastructure
previously put into place for the BA-39 project. This project
will complement existing restoration projects in the area.

CWPPRA Region 2, Barataria Basin, Jefferson and
Plaquemines Parishes. The general project area is about 10
miles south of Belle Chasse, LA and is west of LA Hwy
23 and north of the Myrtle Grove Marina. The project
is immediately adjacent to the completed CWPPRA
Mississippi River Sediment Delivery System – Bayou
Dupont (BA-39) project.

The project was approved for engineering and design at the
January 24, 2013 Task Force meeting. The E&D was
completed in the fall of 2014 and sponsors requested phase
2 funding at the January 22, 2015 Task Force meeting,
however, there was insufficient money available to fund
the entire project. In order to take advantage of the existing
mobilization of the Long Distance Sediment Pipeline
(LDSP) Project, the sponsors proposed to reduce the scope
of the project to fit within the available CWPPRA funding.
The Task Force approved the reduced scope Phase 2 funding
request at the May 14, 2015, Task Force meeting. The asbuilt
project features include 144 acres of marsh creation and
9,679 linear feet of terracing.

In addition, CPRA increased the marsh creation feature of
the project by utilizing contingency funding left over from
BA-43, thereby increasing the total marsh creation in the
area to an estimated 296 acres. Construction started in April
2016, and marsh creation was completed in November
2016. Terracing was completed in June 2017, and vegetative
plantings for the terraces are scheduled for the spring of
2018.

This project is on Priority Project List (PPL) 22.

The Bayou Dupont Sediment Delivery – Marsh Creation and Terracing sponsors include:

• Federal Sponsor: U.S. Environmental Protection Agency 
• Local Sponsor: Coastal Protection and Restoration Authority