Atchafalaya Sediment Delivery (AT-02)

A bucket dredge is shown removing sediment from a shoaled-in channel in order to help reestablish water and sediment flow within the Atchafalaya Delta.

Location

The project is located east of the lower Atchafalaya River navigation channel in the Atchafalaya River Delta, approximately 19 miles southwest of Morgan City, Louisiana, in St. Mary Parish.

Problems

Growth of the lower Atchafalaya Delta has been reduced as a result of maintenance of the Atchafalaya River navigation channel. Delta development in the shallow waters of Atchafalaya Bay is dependent on distributary flows and the diversion of sediments into over-bank areas through crevasse channels.

Because of the placement of material dredged from the navigation channel and sediment accumulation within the channels that decrease flow efficiency, the open crevasse channels are frequently short-lived. As riverflow through a crevasse channel is reduced, the amount of sediment that can be deposited in the delta is likewise reduced, resulting in decreased marsh development.

Restoration Strategy

The purpose of this project is to promote natural delta development by reopening two silted-in channels and using those dredged sediments to create new wetlands. Approximately 720,000 cubic yards of sediment were dredged from Natal Channel and Castille Pass in 1998. Over 12,000 feet of channel were reopened, and more than 280 acres of new habitat were created by the strategic placement of the dredged channels’ sediments. By reestablishing water and sediment flow into the eastern part of the Atchafalaya Delta, an additional 1,200 acres of new habitat are expected to be naturally created over the life of the project.

Progress to Date

Construction was completed in 1998. A pre- versus post-construction habitat analysis using aerial photography indicated that, while there was an increase in land of 78.4 acres, the majority of the habitat created was represented by forested wetland (50.1 acres), while fresh marsh and upland barren habitats accounted for 14 acres gain each. Although many of the dominant plant species are present in both created and reference areas, the created areas contained different plant communities when compared to any time period in the development of a natural crevasse splay that served as a reference area for this project. Although the long-term effects on submerged aquatic vegetation (SAV) are unclear, habitat mapping indicated an increase in SAV habitat of 221.5 acres from 1997 to 1998, but this is very close to the increases that were reported in the project area pre-construction. Satellite imagery indicates that there have been significant increases in emergent acreage from 1998 to 2008.

This project is on Priority Project List 2.

The Federal Sponsor is National Marine Fisheries Service.

The Local Sponsor is CPRA.

East Catfish Lake Marsh Creation and Shoreline Protection (TE-157)

Aerial view of marsh creation project in Terrebonne Parish.

Location

The project is located in Region 3, Terrebonne Basin, Terrebonne Parish.

Problems

Significant marsh loss has occurred east and south of Catfish Lake. Causes of marsh loss include the construction of numerous oil/gas canals, subsidence, and sediment deprivation. Between Catfish Lake and Golden Meadow Hurricane Protection Levee, very little marsh remains after the construction of an extensive network of oil/gas canals. Much of the remaining land in this area consists of spoil banks and isolated patches of marsh. From examination of aerial photography, the majority of this loss occurred during the 1960s and 1970s. Based on the hypertemporal analysis conducted by USGS for the extended project boundary, the land loss rate in the project area is -0.86% per year for the period 1984 to 2019. Shoreline erosion rates (1998-2017) range from 10 ft/yr along the eastern lake shoreline to 22ft/yr along the southern lake shoreline.

Restoration Strategy

The primary goal of this project are; 1) restore marsh habitat in the open water areas east and south of Catfish Lake, and 2) restore and protect the eastern and southern Catfish Lake shoreline. The specific goals of this project are; 1) create 235 acres of marsh, 2) nourish 71 acres of marsh, 3) protect the marsh creation cells from shoreline erosion.

Service goals include restoration/protection of habitat for threatened and endangered species and other at-risk species. This project would restore habitat potentially utilized by the black rail, which is proposed for listing as a threatened species. The project could also benefit other species of concern including the saltmarsh topminnow and seaside sparrow.

Sediment from Catfish Lake will be hydraulically dredged and pumped via pipeline to create/nourish 306 acres of marsh. Dewatering and compaction of dredged sediments should produce elevations conducive to the establishment of emergent marsh and within the intertidal range. Containment dikes will be constructed around each marsh creation cell. Where practicable, material will be borrowed from perimeter oil/gas canals. Containment dikes will be gapped at the end of construction or by TY3. Approximately 2,566 linear feet of sheet pile wall will also be installed as a containment feature. Approximately 12,479 linear feet of shoreline protection (gabion mattresses) will be installed along the lakeside boundary of the marsh creation cells on the constructed containment dikes.

The project was approved for Phase I Engineering and Design in January 2020.

The project is on Priority Project List (PPL) 29.

The Federal Sponsor is US Fish & Wildlife Service.

The Local Sponsor is CPRA.

Phoenix Marsh Creation – East Increment (BS-42)

Degraded marsh in coastal Louisiana.

Location

The project is located in Region 2, Breton Basin, Plaquemines Parish.

Problems

Two major causes of wetland loss for this area are sediment deprivation and saltwater intrusion. Altered hydrology and oil/gas development have exacerbated this loss. Much of the fresh and intermediate marsh that once existed earlier in this century has either converted to more saline habitats or has become open water as a result of oil/gas canals, subsidence, and a lack of sediment deposition. The 1984 to 2019 USGS land change rate is -0.78% per year.

Restoration Strategy

The project goal is to restore 392 acres of marsh in the open water areas between Bayou la Croix and River aux Chênes through the placement of dredged material via hydraulic dredging. This project will work syngeristically with projects to the east by creating continuity with the Breton Landbridge Marsh Creation (West) Project (BS-38) and the Mid Breton Landbridge Marsh Creation and Terracing Project (BS-32). This proposed first increment would extend the reach of the Breton Landbridge and is part of an overall, long-range, restoration goal to create/nourish 1,000 to 2,000 acres of intermediate marsh across 5 miles of the Breton Sound Basin from River aux Chênes to the Mississippi River.

Sediment will be hydraulically dredged from the Mississippi River. The dredged riverine sediments will be pumped via pipeline into two semi-confined disposal areas. Where feasible, existing marsh will be used as containment instead of containment dikes.

Vegetative plantings are not proposed in the marsh creation areas, and containment dikes will be gapped no later than year three post construction.

Service goals include restoration/protection of habitat for threatened and endangered species and other at-risk species. This project would restore habitat potentially utilized by the black rail, which is proposed for listing as a threatened species. The project could also benefit other species of concern including the saltmarsh topminnow and seaside sparrow.

The project was approved for Phase I Engineering and Design in January 2020.

The project is on Priority Project List (PPL) 29.

The Federal Sponsor is US Fish & Wildlife Service.

The Local Sponsor is CPRA.

North Delacroix Marsh Creation and Terracing (BS-41)

NOAA staff gather data to inform project design. 

Location

The project is located in Region 2, Breton Basin, St. Bernard Parish.

Problems

Hurricanes Katrina and Rita caused the majority of wetland loss in the project site. Wind erosion and saltwater intrusion have resulted in loss of marsh vegetation and wetland soils. Marsh loss has increased exposure of Delacroix to flooding from the east/ southeast. The 1984 to 2019 USGS loss rate is -1.4%/ year for the extended project boundary area.

Restoration Strategy

The project goal is to create and nourish approximately 389 acres of marsh and construct approximately 8,548 linear feet of terraces utilizing a layout to help protect the community of Delacroix.

Sediment would be hydraulically dredged from Lake Lery and placed into two confined disposal areas creating 322 acres of marsh and nourishing 67 acres of existing marsh. Two creation cells allow a channel for drainage. Approximately 8,548 ft of earthen terraces would be constructed. The terraces would be strategically placed east of the northern marsh creation cell and south of the southern cell. Dewatering of the marsh creation cells into areas adjacent to the terraces would take advantage of sediment laden water trapping the particulates to create additional marsh. Terraces would be planted with appropriate bare root plants 2.5 ft apart in one row per side and crown. Created marsh will not be planted.

Containment dikes will be gapped no later than three years after construction. Two additional areas of deteriorating marsh south and east of the proposed project will be investigated. Data acquisition for engineering and design would include an additional
349 acres to allow robustness for these additive or alternate features during Phase I.

The project was approved for Phase I Engineering and Design in January 2020.

This project is listed on Priority Project List 29.

The Federal Sponsor is NOAA NMFS.

The Local Sponsor is CPRA.

Hurricanes

This week marks 13 years since Hurricane Katrina, an event some citizens of Louisiana are still recovering from. We may have all heard the name, but do we know what a hurricane is, how wetlands are affected, and how coastal landforms can decrease hurricane impacts?

“Hurricanes” are low-pressure tropical storm systems that differ from other storms in severity as well as location. A hurricane is a storm with winds above 64mph accompanied by heavy rain that originates in either the NE Pacific or the N Atlantic Ocean (the oceans that touch the USA). Due to a phenomenon called the Coriolis Effect, hurricanes rotate counter-clockwise, whereas a southern hemisphere storm would rotate clockwise. Hurricanes develop a characteristic “eye of the storm” in the center, which is an area of low pressure and low wind. Just outside of the eye is the most severe weather, the eyewall, with winds reaching up to 210mph in the strongest storms! Hurricane “category” ratings are as follows:

• Category 1: 74-93mph
• Category 2: 96-109mph
• Category 3: 110-129mph
• Category 4: 130-157mph
• Category 5: >158mph

Hurricanes develop over areas with warmer waters, typically nearer the equator, and move away from the equator. [1] Coastal Louisiana is hit by hurricanes on an increasingly regular basis, and those hurricanes all develop in the North Atlantic Ocean in late summer and fall. Our “Hurricane Season” occurs from June through November each year. [2] Several aspects of hurricanes pose major threats to our wetlands statewide. High winds can topple trees, rip up shrubs and grasses, and move sediments around. High rainfall can cause flooding in areas that are not well-adapted to high-water conditions. Storm surge can push saline seawater into brackish and freshwater systems. Hurricanes cause massive disturbance in coastal wetlands, but wetlands are a crucial barrier that protects major cities from taking as much damage. CWPPRA works to combat land loss and protect the future of coastal Louisiana.

Some CWPPRA projects restore barrier islands, which are natural defenses that develop in the Deltaic Cycle. Barrier islands lessen storm surge during hurricanes, bearing the brunt of the waves. Sadly, they cannot provide perfect protection because they are degrading, but they are not the last line of defense. We still have coastal marshes that are great at storing water and acting like a speed bump to storm surge. It is estimated that each mile of coastal marsh decreases storm surge by about a foot. Unfortunately, many coastal marshes are decaying into open water and are no longer protective barriers. CWPPRA will continue to restore wetlands and nourish barrier islands to #ProtectOurCoast!

 

[1] https://en.wikipedia.org/wiki/Tropical_cyclone

[2] https://www.ready.gov/hurricanes

Featured image from [1]