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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Featured Image Source: https://bit.ly/2MjEIyA
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Measuring Water Quality

Many wetlands of Louisiana receive their freshwater input from the Mississippi river, whose watershed drains approximately 40% of the United States’ waterways. [https://www.nps.gov/miss/riverfacts.htm] Pollutants get into the river from nonpoint sources, which are things like agricultural runoff, urban runoff from roads and sewage, or precipitation of atmospheric compounds, and thus they are spread into Louisiana’s wetlands.[3] Excessive pollutants deteriorate wetlands because they kill vital plants and animals in the ecosystem, which has feedback onto other species. Before interfering with anything in an ecosystem, we need to understand how the ecosystem functions.

Water quality plays a huge role in keeping wetlands healthy. The term “water quality” refers to several characteristics of a body of water, including salinity, nutrient concentration, turbidity, and dissolved oxygen [1]. These factors contribute to how well individuals can live and grow in the ecosystem associated with that body of water. For example, some plants and animals have a strong preference for either high or low salinity (See Salinity Stress Tolerance article), some prefer higher water levels (see Flooding and Hypoxia article), and some can live in many combinations of conditions.

Turbidity is a measure of how much suspended sediment is in the water column. Higher turbidity causes less light to penetrate to the deeper layers, so highly turbid waters often have less submerged aquatic vegetation. Turbidity can be measured with a Secchi disk or Secchi tube. Dissolved oxygen is important to aquatic plants because they still need to exchange oxygen to carry out their metabolic processes. Dissolved oxygen is measured by either luminescence sensors or electrode oxidation. [2] Many of the instruments that measure different aspects of water quality are combined into a Multiparameter Water Quality Sonde to get multiple measurements from the same sample of water. More information on specific procedures and equipment for measuring water quality can be found at https://www.fondriest.com/environmental-measurements/equipment/measuring-water-quality/.

Measuring water quality as a way of determining wetland health is important to many CWPPRA project locations. Measurements allow ecologists to determine any potential risks or threats from developing a project to the integrity of site’s established ecosystem. Fragile ecosystems can be drastically affected by constructing a project because the projects are likely to alter hydrology, salinity, and may introduce conditions that residents cannot survive. Forming a profile of water quality helps to predict the project’s positive and negative outcomes, and to predict the success and longevity of the project.

 

[1] https://www.fondriest.com/environmental-measurements/parameters/water-quality/

[2] https://www.ysi.com/parameters/dissolved-oxygen

[3] https://www.epa.gov/nps/basic-information-about-nonpoint-source-nps-pollution

Featured image from https://phys.org/news/2017-01-technique-quickly-salt-marsh-vulnerability.html

Measuring Elevation Change

To provide the best possible care, doctors first must know what is going on with their patients. The same goes for ecologists and engineers with wetlands. Just like doctors can measure your growth and deduce what could help you get over a sickness, ecologists measure the “health” of ecosystems to try to keep them healthy.

Wetland habitats have many moving parts which makes them difficult to fully understand, but we can get a pretty good idea of whether they are growing or deteriorating and sometimes why. All CWPPRA projects require significant amounts of research to estimate the benefit of the project and minimize any damage that could come from disturbing already established wetlands. CWPPRA funds the Coastwide Reference Monitoring System (CRMS) program, which provides reliable coastal elevation data to scientists. Completed projects are monitored for wetland health factors including land accretion, productivity, and water quality to determine whether they are making a positive impact on coastal systems.

Elevation studies are necessary across our coast since we experience such high levels of sediment subsidence. Elevation can be measured in a variety of ways, such as geodetic leveling, Interferometric Synthetic Aperture Radar (inSAR), or satellite imaging. [1] Because of the lower precision, satellite imaging is not great for measuring elevation change for a specific point but is relatively reliable for larger changes over longer periods of time. Another common technique for measuring elevation change in wetland ecology is Rod Surface Elevation Tables with Marker Horizons (RSET-MH), which is implemented at all CRMS sites.

 

. Rod surface elevation table - marker horizon (RSET-MH) in both shallow and deep configurations. All installations associated with the current work will be deep. 
RSET-MH diagram with deep benchmark, shallow benchmark, marker horizon [2]
An RSET is attached to a deep benchmark that will resist erosion and accretion, somewhere between 20 and 25 meters below the surface of the marsh, where the hard-packed sediments lie. With a benchmark, scientists can measure the relative surface elevation . To measure the rate of sediment accretion between two time periods researchers deposit a layer of white clay on the soil’s surface, called a marker horizon. At a later date, researchers return to the site, collect a core sample, and measure the amount of sediment above the white clay to calculate an accretion rate. [3] RSET-MH is great for measuring one specific site for small and precise elevation changes, but is limited in area coverage. Luckily, through the Coastwide Reference Monitoring System, we are able to monitor elevation change and accretion rates at over 390 sites across the coast!

Measuring wetland health has many factors, not only elevation change. Check in next week for our next installment on wetland monitoring!

 

[1] https://www.epa.gov/wetlands/wetlands-monitoring-and-assessment

[2] https://www.researchgate.net/figure/Rod-surface-elevation-table-marker-horizon-RSET-MH-in-both-shallow-and-deep_fig2_281113921

[3] https://www.pwrc.usgs.gov/set/

Featured Image from https://oceanservice.noaa.gov/sentinelsites/chesapeake-bay/welcome.html

Capitol Park Museum Outreach event

On July 7th, 2018, the CWPPRA Public Outreach team spent the day at the Capitol Park Museum in Baton Rouge, LA, talking to museum visitors. We were the special exhibit for the museum’s ‘First Saturday Family Program’ series. As the special exhibit, we were set up near the entrance, and we caught the eyes of all who entered the building. Visitors competed in Wetland Jeopardy, took silly pictures in our photo booth, and matched beanbag animals to their wetland homes! We also had Protect Our Coast posters, recent issues of WaterMarks, activity books, and other publications available.

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The Museum hosts many special exhibits, which can be found on their calendar here. https://louisianastatemuseum.org/museum/capitol-park-museum

We were fortunate to have this time in a great museum full of Louisiana history. The regular exhibits included Plessy v. Ferguson, sport hunting and fishing, the civil war, the Mississippi steamboats, and native tribal history. There were several exhibits on large local industries like farming, oil, and fisheries as well. Coastal wetlands are an important resource that all Louisianans share, contributing to storm protection, the economy, and recreational opportunities, and visitors to the museum had the opportunity to connect CWPPRA’s restoration work with the colorful history and culture of Louisiana.

West Belle Pass Barrier Headland Restoration (TE-52)

wordpress fact sheet banner TE-52-01.pngThis headland experiences some of the highest shoreline retreat rates in the nation, measuring over 100 feet a year in some locations. As the gulf encroaches upon the shoreline, sand is removed and the headland erodes. What was once a continuous shoreline spanning several miles has been reduced to less than half its original length. Furthermore, Hurricanes Katrina and Rita removed most of the emergent headland and dunes west of the pass. This headland helps provide protection to interior marshes and the Port Fourchon area; however, its continued degradation threatens the fragile bay habitat and infrastructure it once protected.

This project will reestablish the West Belle headland by rebuilding a large portion of the beach, dune, and back barrier marsh that once existed. Approximately 9,800 feet of beach and dune will be rebuilt using nearly 2.8 million cubic yards of dredged sand, and 150 acres of marsh habitat will be rebuilt using nearly 1.4 million cubic yards of dredged material. Native vegetation will be planted upon construction to help stabilize the rebuilt marsh and dune habitat.

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The project is located along the Chenier Caminada headland to the west of West Belle Pass, at the southeastern edge of Timbalier Bay in Lafourche Parish, Lousiana.

This project was approved for engineering and design in October 2006. Construction funds were approved by the Task Force in late 2009, construction began fall 2011, and construction was completed in October 2012.

This project is on Priority Project List 16.

Federal Sponsor: NOAA NMFS

Local Sponsor: CPRA

Coastal Parks and Refuges

Coastal Louisiana boasts an impressive number of state parks that span a variety of ecosystems. Many of the parks contain salt or fresh wetlands, and each is unique; cypress-willow-tupelo swamps, pine forests, cordgrass marshes, and grass-dominated prairie, to name a few. Tourists are very fortunate to have so many different choices when planning their trips. For example, hiking and camping in a bottomland hardwood forest can be found at Chicot State Park, beaches and boating can be done at Grand Isle State Park, and a mix of fresh and salt water fishing can be found in Bayou Segnette State Park. Many of these parks offer a birding guide to help with identifying migratory songbirds, wading birds, and many others. A complete list of Louisiana State Parks can be found at https://www.crt.state.la.us/louisiana-state-parks/parks/index.

As impressive as the state parks may be, they are not the only parks in Louisiana. Louisiana is home to 23 National Wildlife Refuges, 8 National Parks, and 1 National Forest, among other attractions. CWPPRA has several projects within national refuges that have helped to maintain the appeal of our natural splendor to visitors. Through hydrologic restoration which helps freshwater move into coastal areas, marsh creation to increase existing land, and shoreline protection to combat erosion, we hope to preserve the areas like Cameron Prairie NWR, Big Branch Marsh NWR, and Rockefeller State Wildlife Refuge in a way that they can be enjoyed for many years to come. With such vibrant ecosystems, it is no wonder .

More information about the national wildlife refuges can be found at https://www.fws.gov/refuges/refugelocatormaps/louisiana.html

More information about the national parks can be found at  https://www.nps.gov/state/la/index.htm

 

Featured image from  https://www.birdwatchersdigest.com/bwdsite/explore/regions/southeast/louisiana/louisiana-birding.php

South Lake Lery Shoreline & Marsh Restoration (BS-16)

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Reasons for Restoration:

According to USGS-land loss analysis, much of the southern and western shorelines of Lake Lery and the surrounding wetlands were heavily damaged in 2005 by Hurricane Katrina. In the years following this storm, wind induced waves within the lake have begun to cause further damage to the lake’s shorelines. Currently the shorelines have become so damaged that the interior emergent marshes that are still intact are being exposed to the damaging waves. This has caused an increased loss of emergent marsh habitat. Even with the benefits of the Caernarvon Diversion Structure, without some type of restoration in this area, these marshes may not be able to fully recover.

Restoration Strategy:

This is a marsh creation and shoreline restoration project. The marsh creation aspect of the project will have a hydraulic dredge extract material from the Lake Lery water bottom and pump that material into contained marsh creation cells located south and west of the southern and western Lake Lery shorelines. This will create and/or nourish approximately 642 acres of intertidal intermediate marsh. The shoreline restoration component of the project will  have a barge-mounted dragline excavating material from the bottom of Lake Lery and placing that material along the southern and western shorelines. This restored shoreline will have a 50 foot crown width and be built to a height considered high intertidal marsh.

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Progress to Date:
This project received Phase II funding in January 2012. Construction began in the spring of 2015 and is expected to be complete in the summer of 2018. All marsh creation is complete. Earthwork and vegetative plantings associated with the lake rim embankments are complete. There are ongoing discussions regarding erosion concerns along lake rim embankments.
This Project is on Project Priority List 17.

The Sponsors for this Project include:

sponsors_1.pngFederal Sponsor: U.S. Fish and Wildlife Service

Local Sponsor: CPRA