Delta Wide Crevasses (MR-09)

The Mississippi River Delta is one of the hallmark symbols of Louisiana’s rich natural heritage. Unfortunately, natural and man-made alterations to the Mississippi River have changed the hydrology of the river and impeded the natural wetland building processes in the delta. Levees constructed for navigation maintenance and flood control have reduced natural sedimentation and freshwater flow, causing deterioration of wetlands and saltwater intrusion. Crevasses are breaks in the levees that allow the river to deposit sediments into adjacent shallow bays. The wetlands formed from the deposition of these sediments are called crevasse splays. This restoration project mimics the natural process of crevasse formation that was responsible for building much of the Mississippi River Delta.

The project consists of maintaining presently existing crevasse splays, the construction of new crevasse splays and plugs, and future maintenance of selected crevasse splays in both the Pass a Loutre Wildlife Management Area and the Delta National Wildlife Refuge. The objective is to promote the formation of emergent freshwater and intermediate marsh.

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The project is located in Plaquemines Parish, Louisiana, within the Pass a Loutre Wildlife Management Area (Louisiana Department of Wildlife and Fisheries) and the Delta National Wildlife Refuge (U.S. Fish and Wildlife Service).

The first dredging cycle of construction was completed in 1999; three dredging cycles are scheduled in the future. The second cycle is scheduled for early summer 2004.

This project is listed on Priority Project List 6.

The Federal Sponsor is NOAA NMFS

The Local Sponsor is CPRA

Delta Management at Fort St. Philip (BS-11)

Since the crevasse, the area has been in a state of transition. It was once an organic, low-energy system consisting of brackish-saline marsh and was in decline. After the crevasse, it became a deltaic environment dominated by the formation of fresh and intermediate marshes.

GIS analysis indicates that marsh loss has decreased considerably in the project area, and marsh building has begun to occur. Many areas that historically experienced marsh loss were becoming shallower with the introduction of river sediments.

Emergent marsh has been forming throughout the area on the newly accreted mineral soils. Even though this area has experienced a net gain in emergent marsh, this project will enhance the natural marsh-building processes and increase the growth rate of emergent wetlands.

The project included the construction of terraces in open water habitat and the construction of six crevasses to increase marsh-building processes.

The terraces were planted with seashore paspalum (Paspalum vaginatum) and smooth cordgrass (Spartina alterniflora).

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The project is located on the east side of the Mississippi River near the crevasse (a break in the levee) that formed during the 1973 flood at Fort St. Philip in Plaquemines Parish, Louisiana.

The construction contractor mobilized to the project site in June 2006. A barge-mounted bucket dredge was used to construct the crevasses while marsh-buggy backhoes constructed the terraces. The six crevasses were completed in August 2006 with completion of the terraces in November 2006. A final inspection was conducted on December 4, 2006.

This project is on Priority Project List 10.

The Federal Sponsor is USFWS

The Local Sponsor is CPRA

Mississippi River Sediment Delivery System – Bayou Dupont (BA-39)

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Marshes in the project area have degraded to open water with only scattered clumps of low-lying vegetation remaining. Marsh degradation has resulted from a combination of lack of natural fresh water and sediment input, subsidence and the dredging of oil and gas canals.

The proposed project included dredging sediment from the Mississippi River for marsh creation and pumping it via pipeline into an area of open water and broken marsh west of the Plaquemines Parish flood protection levee. The material was spread over the project area and ontained primarily with existing land features. Newly-constructed low containment dikes were necessary only along a limited portion of the project area. Native intertidal marsh vegetation was planted post construction.

The proximity of the project to the Mississippi River presented a prime opportunity to employ a pipeline delivery system that utilized the sediment resources from the river to restore and create wetlands. Unlike most marsh creation projects that involve borrowing fill material from adjacent shallow water areas within the landscape, this project utilized renewable river sediment, thus minimizing disruption of the adjacent water and marsh platform.

The Bayou Dupont project represents the first example of pipeline transport of sediment from the river to build marsh as a CWPPRA project. Results from this project helped demonstrate the value and efficacy of greater use of pipeline-conveyed river sediments for coastal restoration.

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The project is located adjacent to Bayou Dupont and southeast of Cheniere Traverse Bayou in the vicinity of Ironton in Plaquemines Parish and Lafitte in Jefferson Parish, Louisiana. The general area lies west of LA Hwy 23 and just north of the Myrtle Grove Marina within the Barataria Basin.

Phase 1 was approved in January 2003. The Louisiana Department of Natural Resources (LDNR) Coastal Engineering Division performed the engineering and design services. Design was completed in November 2007; Phase 2 was approved in February 2008, and construction activities began in April of 2009. Approximately 25,935 linear feet of containment dike was used to create approximately 484 acres of sustainable marsh in Marsh Creation Areas 1 and 2. Increment 2 (funded through ARRA) added approximately 84 acres of marsh within 6,241 linear feet of containment dikes. The contractor demobilized completely by May 10, 2010. Final inspection was held on May 25, 2010.

This project is on Priority Project List 12.

The Federal Sponsor is EPA

The Local Sponsor is CPRA

Raccoon Island Shoreline Protection/Marsh Creation (TE-48)

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The Isles Dernieres barrier island chain is experiencing some of the highest erosion rates of any coastal region in the world. Raccoon Island is experiencing shoreline retreat both gulfward and bayward, threatening one of the most productive wading bird nesting areas and shorebird habitats along the gulf coast.

An existing demonstration project on the eastern end of the island, Raccoon Island Breakwaters Demonstration project (TE-29), has proven that segmented breakwaters can significantly reduce, and perhaps even reverse, shoreline erosion rates. The primary goal of this project is to protect the Raccoon Island rookery and seabird colonies from the encroaching shoreline by: 1) reducing the rate of shoreline erosion along the western, gulfward side and 2) extending the longevity of northern backbay areas by creating 60 acres of intertidal wetlands that will serve as bird habitat.

This project has been separated into two construction phases, Phase A and Phase B. Phase A includes the construction of eight additional segmented breakwaters gulfward of the island and immediately west of the existing breakwaters demonstration project and an eastern groin that will connect existing Breakwater No. 0 to the island. Phase B involves the construction of a retention dike along the northern shore to create a back bay enclosure that will be filled with sediments dredged from the bay and/or gulf, followed by vegetative plantings.

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The project is located in the Terrebonne Basin on the western-most island of the Isles Dernieres barrier island chain in Terrebonne Parish, Louisiana.

Rock breakwater construction for the prior demonstration phase of this project was completed on the east end of the island in June 1997. Sand deposits or “tombolos” have developed behind the breakwaters that protect and enhance the island. A less dramatic, however still positive effect, is expected to occur behind the 8 additional breakwaters being constructed to the west of the existing breakwaters.

Construction of Phase A was completed in September 2007 and Phase B in June 2013. All plantings are to be completed by the end of 2017.

This project is on Priority Project List 11.

The Federal Sponsor is USDA NRCS

The Local Sponsor is CPRA

Humble Canal Hydrologic Restoration (ME-11)

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The Grand and White Lakes system has been maintained
as a fresh-to-intermediate marsh environment. This has
been accomplished through water management using
natural ridges, levees, locks, and water control structures.
This project replaces the Humble Canal structure that has
fallen into disrepair. This project is compatible with the
overall basin strategy of treating critical areas of marsh
loss within the interior of the basin and managing water
levels with structures to relieve stress on interior wetlands.
The project also relieves this area from continued saltwater
intrusion from the Mermentau River that threatens the
viability of the fresh to intermediate marshes within the
region.

The objective of this project is to restore historical
hydrology to the project area by constructing a water
control structure consisting of five 48-inch diameter by 50-
foot long corrugated aluminum pipes with flap gates and
weir drop inlets along with one 18-inch diameter
corrugated aluminum pipe with screw gate. This structure
will protect the area from Mermentau River saltwater
intrusion and allow high water to drain from the marsh to
the river. Dredging of a small waterway is included to
increase the effectiveness of the structure.

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The project is located in the Mermentau basin, on the west
bank of the Mermentau River approximately 2 miles
southwest of Grand Lake at the Humble Canal in Cameron
Parish, Louisiana.

Construction of the project was completed March 5, 2003.
The project is now in the operation and maintenance phase.

This project is on Priority Project List 8.

 

Federal Sponsor is NRCS

Local Sponsor is CPRA

Four Mile Canal Terracing and Sediment Trapping (TV-18)

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The main cause of current marsh loss is a shoreline erosion
rate of approximately 8 feet/year. A combination of wind
and wake energy prevents sediments introduced by the Gulf
Intracoastal Waterway (GIWW) via the Vermilion River and
Four Mile Canal from allowing subaerial marsh development
in the area.

Reduction of shoreline erosion will be achieved by the
buffering capacity of the constructed terraces. The proposed
terrace layout is very different for each area of the project.
The “fish net” design for Little Vermilion Bay is designed to
allow sediment deposition and the terraces in Little White
Lake are aligned to reduce the wind generated waves, thus
reducing shoreline erosion. Thus, marsh habitat will be
created in two ways within the Four Mile Canal Terracing
Project area. First, marsh will immediately be built by
creating approximately 90 terraces from dredged material
and planting them with smooth cordgrass. This action alone
will create 70 acres of subaerial land. Second, by reducing
fetch and wave energy, terraces will promote the deposition
of suspended sediments in the shallow water adjacent to
the terrace edges in Little Vermilion Bay and Little White
Lake. This will slowly build marsh over the life of the
project as subaerial land is built and plants naturally become
established.

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The project is located approximately 4 miles south of
intracoastal City in Vermilion Parish, Louisiana. The
project area includes all of Little White Lake and part of the
northeastern embayment of Little Vermilion Bay.

Project construction was completed in May 2004. No
maintenance activities have been undertaken as of 2017
and none are planned prior to project closeout. While some
terraces have eroded since construction, in general the
project is in good condition and functioning as intended.
Shoreline erosion has decreased and wetland acreage has
increased since construction.

This project is on Priority Project List 9

The Federal Sponsor is NOAA NMFS

The Local Sponsor is CPRA

Barataria Bay Waterway East Side Shoreline Protection (BA-26)

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The banks of the Dupre Cut have eroded considerably as a
result of vessel wakes. Large breaches in the banks
exposed the adjacent marsh to increased water exchange,
tidal energy, and saltwater intrusion.

The objective of this project was to rebuild and stabilize
the east bank of the Dupre Cut. A stronger bank would
reduce erosion and help reestablish wetlands by allowing
sediment accretion on the leeward side of the foreshore
rock dike.

The project plan involved the construction of over 3 miles
of foreshore rock dike along the east bank of the Dupre
Cut to protect adjacent marshes from shoreline erosion.
This rock dike extends above the surface of the water and
will protect the fragile marsh area from boat wakes
generated within the BBWW.

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The project is located in Jefferson Parish, Louisiana, on
the east bank of the Dupre Cut portion of the Barataria Bay
Waterway, north of the Lafitte Gas and Oil Field and south
of the subsided land reclamation effort known as “the
Pen.”

 

Construction was completed in June 2001. Baseline
monitoring information has been collected and will be
used to evaluate the project’s effectiveness. The O&M
Plan was signed in October 2002. This project is on
Priority Project List 6.

The Federal Sponsor is NRCS.

The Local Sponsor is CPRA.