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

Microorganisms Help Wetlands

Seeing microorganisms and cellular structures brought about a new era of scientific discovery, from understanding infectious agents to recognizing sub-cellular structures in living tissues. Microscopy allows us to observe the smallest parts of our natural world invisible to the human eye. Different types of microscopes and other analyzing tools have allowed ecologists and environmental scientists to assess the health of wetlands in coastal Louisiana. From geologists to botanists, sedimentologists to ecologists, microorganisms are a vital ally in the fight against wetland loss in coastal Louisiana.

Microorganisms like phytoplankton (microscopic plants) can be great indicators of aquatic and wetland habitat health because they are easily affected by changes and easy to observe under a microscope. Studies across the Gulf Coast sample phytoplankton and zooplankton (microscopic animals) to keep tabs on large-scale changes in water quality. For example, algal blooms, which are huge growths of phytoplankton, often lead to the death of important fisheries species. These blooms also indicate poor water quality and contribute to the worsening of hypoxia.

Soil microbes can give information on marsh platform health. In response to stressful situations, these microbes can change their cell walls’ chemical makeup to reduce physiological damage. By identifying both the stressed and non-stressed types of molecules, soils can be assessed quickly. Healthy soils are important in keeping nutrients cycling, which is crucial in keeping wetland plants alive and growing.  Without a stable microbiome supporting plant growth, marsh platforms degrade and can no longer sustain life or provide any ecosystem services.

Microscopic organisms also play a huge role in coastal Louisiana’s wetlands because they are crucial in regulating marsh platforms, feeding our fisheries, and producing a huge portion of atmospheric oxygen for all terrestrial life on the planet. Coastal scientists study these tiny indicator species to quantify the health of wetland ecosystems. For example, fisheries rely on trophic interactions (food web/food chain) that include phytoplankton as the primary producers. Since seafood is such a profitable industry in Louisiana, we have a great appreciation for microbes. Louisiana’s crucial shrimp harvest and signature oysters rely directly on plankton, and larger sport fish rely on eating other things that eat plankton.

Although tiny, microorganisms play an important role in Louisiana’s coastal wetlands. As complex a system as our coast is, it’s easy to see direct impacts that a weak microbial community may have on certain pieces of the full ecosystem. We urge our scientists, engineers, and legislators to be conscious of each problem our coastal zone faces and the tricky side effects that may come with them. When restoring our coast, we must look at the big picture as well as the key parts involved in our coastal wetland system!

 

Sources:

https://www.epa.gov/national-aquatic-resource-surveys/indicators-zooplankton

https://link.springer.com/article/10.1007/s100400050013

https://www.researchgate.net/profile/Colin_Jackson11/publication/225750153_Effects_of_Salinity_and_Nutrients_on_Microbial_Assemblages_in_Louisiana_Wetland_Sediments/links/587e38e408ae4445c06fac52/Effects-of-Salinity-and-Nutrients-on-Microbial-Assemblages-in-Louisiana-Wetland-Sediments.pdf

Featured image of a Haptophyte from https://johandecelle.wordpress.com/2014/10/02/a-novel-diversity-of-haptophytes-unveiled-by-metabarcoding/

Land Loss and Human Impacts

Louisiana’s shrinking coastal zone is due to both natural causes such as rising sea levels and wave erosion, but human activity intensifies these evolutionary processes. Some of the most impactful land loss processes further increased by human activity include salt water intrusion, proliferation of invasive species, and subsidence.

Hurricanes and other storm events push salt water inland, increasing the salinity of wetlands to levels that damage local flora adapted to lower salinities, causing those plants to die, which in turn decreases their potential to reduce storm surge around human settlements. Dredged canals for oil and gas exploration provide easy pathways for salt water to move inland since these canals are often straight. [1] Healthy marshes decrease the distance that storm surges can infiltrate, so any man-made development that diminishes intermediate or salt marshes indirectly affects freshwater wetlands as well.

Invasive species are plants, animals, or other biota that are from other regions of the world that cause harm to our local native environment. One such invasive species with extensive ramifications for our coastal wetlands is the Coypu, or “nutria rat.” This large rodent devastates stands of native graminoids such as cordgrasses (Spartina spp) and bulrushes (Schoenoplectus spp). Coypu specifically target the base of stems and roots, digging for them in soft sediment platforms. [2] Lower root concentration in soils and active disturbance make for weakened substrates that are more susceptible to being washed away. Other invasive species have similar outcomes, but not necessarily by the same method. We have several invasive animals and plants in Louisiana, each introduced by humans either on purpose or accidentally, and each one has a destructive presence along our coast. CWPPRA actively works to counter the destruction of invasive species through research, engineering and reward-based mitigation, such as the Coastwide Nutria Control Program. [3]

Louisiana was built by the Mississippi River over the past several thousand years, depositing layer after layer of soft, uncompacted sediment. Naturally, that sediment will compact, causing the surface to sink. Developing human settlements might speed up this process due to increased weight. Some cities are sinking as fast as 12 millimeters per year. Combined with rising sea levels, these areas are getting 15 millimeters (.6 inches) closer to sea level each year. [4] Combining the natural subsidence rates with unnatural marsh degradation, flooding will continue to worsen in our towns and cities. The Coastwide Reference Monitoring System (CRMS) tracks subsidence as well as several other ecological conditions and CWPPRA project performance over 391 sites along the Louisiana Gulf Coast. [5] Human activity is an integral component of Louisiana’s coastal zone, and CWPPRA works with biologists, engineers, local governments, volunteers, and residents to study those adverse impacts and devise innovative methods to address and deter them.

 

Sources:

[1] http://web.mit.edu/12.000/www/m2010/finalwebsite/background/wetlands/wetlands-degradation.html

[2] http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Myocastor_coypus.htm

[3] https://www.nutria.com/site9.php

[4] https://www.nola.com/news/environment/article_fc2fc043-f0a3-55a5-b1a5-ce96dc712c3e.html

[5] https://www.lacoast.gov/crms/Home.aspx#

 

Featured Image from JennyCuervo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)%5D

Dynamic and Restored Wetland Habitats

Many animals and a few plants are adaptable to changing conditions in their habitats, which is a vital ability in dynamic landscapes such as wetlands. With seasonal flooding, temperature shifts, storm pressure, nutrient availability, species density and variation, and many other factors, many species are adaptable to changes that are predictable. Unfortunately, there are man-made and natural changes that may disrupt entire ecosystems by destabilizing one “keystone species” or by changing a crucial abiotic factor such as salinity. In coastal restoration, groups like CWPPRA ensure that they are not causing a sudden shift in any ecosystem in which they are working. CWPPRA projects must abide by the results of an Environmental Impact Survey (EIS) to ensure that the proposed project is not going to disrupt key processes including reproductive cycles, migration, or nutrient replenishment.

Freshwater diversion projects are a hot topic on the restoration circuit these days, because although they seek to restore land that has been lost or save areas that are degrading, there are key stakeholders, such as oystermen, who have moved into and now rely on these now-open waters for their livelihood. Restoration groups conduct an EIS for each project to understand the impact of a project for Louisiana’s working people as well as ecosystems.

Coastal Restoration is a complex issue with many intertwined components. Ecosystems are fairly resilient, but they are threatened by large-scale, sudden changes. Storms can increase salinity in freshwater wetlands, which causes many plants and animals to die. Freshwater wetlands are constantly under pressure at their fringes because our coastal zone is moving further and further inland. This shrinkage allows more salinity influence in areas that, historically, were safe behind their salt marshes that are now deteriorating or already lost.

Restoring the coast can’t happen soon enough for the people and other animals that live there, as well as plants and even people who live outside of Louisiana. A recent state poll demonstrates that over half of Louisiana’s residents recognize that coastal land loss will directly impact them this year, and that number jumps to over 75% expecting to be impacted in the next ten years.[1] It is clear that the concern for our rapidly disappearing coast is gaining ground, and CWPPRA stands ready to restore, rebuild and maintain Louisiana’s wetlands for the near-term and the future.

 

[1] http://mississippiriverdelta.org/coastal-poll-2019/

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