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

Watersheds and International Day of Action for Rivers

Water flows from the higher elevations of the northern United States to our low-lying wetlands. Surface elevation, on average, decreases from the northern border with Canada all the way to the mouth of the Mississippi River. What that means is that most of the water that falls between the Rocky Mountains and the Great Smoky Mountains drains into the Mississippi and eventually in the coastal waters of Louisiana. We call this area the Mississippi/Atchafalaya River Basin (MARB) or the Mississippi River Watershed. [1] A watershed, by definition, is an area that drains to a river or lake. The Mississippi River Watershed encompasses nearly 41 percent of the United States.

Streams and ponds in the higher elevations of our watershed are fed by precipitation (rain, snow, hail, etc.) or springs. Water always follows the path of least resistance, which is downhill. Even on gradual slopes, water will seek out lower elevations. Flow rate is dependent on the angle of the slope, also called the elevation gradient. This explains why rivers in more mountainous regions flows faster than in our very flat land. Of course, some water will evaporate, some water will seep into the ground, and the rest will continue downstream until it gets to the ocean. While there are some exceptions to that rule, such as the Great Salt Lake in Utah and other Endorheic basins (no outlets besides evaporation), most water that falls on land will follow the water cycle that we all learned in grade school.

In Louisiana, the MARB outlets are the mouths of the Atchafalaya and Mississippi rivers and their distributaries. Because the state receives this water runoff through our bayous and marshes, so too does it collect  the trash and other pollution from the watershed. This pollution includes not only typical litter and non-point-source runoff, but also agricultural runoff that carries an abundance of nutrients. Select groups across the state are employing litter collection traps in bayous and streams to prevent trash from ending up in our coastal waters. More about these issues can be found in our articles about hypoxia stress and soil pollution.

The International Day of Action for Rivers will be celebrating healthy watersheds worldwide tomorrow, March 14. [2] We encourage our readers to do a little cleaning in their local waterways year-round but especially tomorrow. There are several groups around the state who organize clean-ups in our local waterways for any who are interested. Some of these groups can be found in our sources. As the third largest watershed in the world, the MARB supports numerous ecosystems and human settlements, and it is crucial that we keep it healthy for all its constituents. Each day, our coastal wetlands protect our cities and ports, so we at CWPPRA strive to return the favor and #ProtectOurCoast.

 

[1] https://www.epa.gov/ms-htf/mississippiatchafalaya-river-basin-marb

[2] https://www.internationalrivers.org/dayofactionforrivers

Featured image from http://www.bayouvermilionpreservation.org/photos.html

 

Action groups:

 

City of Lafayette: http://www.lafayettela.gov/EQ/Pages/Environmental-Outreach.aspx

Bayou Vermilion District: http://www.bayouvermiliondistrict.org/

Sierra Club: https://www.sierraclub.org/louisiana/what-do-you-want-do

BREC: http://www.brec.org/index.cfm/page/GroupVolunteerOpportunities

BTNEP: https://volunteer.btnep.org/

2nd Annual Cook-Off for the Coast

Thanks to the Meraux Foundation, the second annual Cook-Off for the Coast played out beautifully on Saturday, February 9th, 2019. CWPPRA was one of many outreach and educational groups hosted at Docville Farm in Violet, LA for an afternoon of good food, good music, and great enthusiasm for coastal restoration. All profits raised by the event went to Chalmette High School and Nunez Community College coastal restoration organizations which will use the funds to continue propagating and planting black mangroves in St. Bernard Parish and installing artificial oyster reef breakwaters just north of Comfort Island east of the current delta. We were set up next to our partner CPRA and under the same tent as Louisiana Master Naturalists of Greater New Orleans, the Louisiana Department of Wildlife and Fisheries, and the LSU AgCenter. Across the lot from us were Restore the Mississippi River Delta, CRCL, and various other restoration-minded groups.

The theme for this year’s cook-off was wild game so all the food that was prepared had some kind of wild game in it, including tuna, oysters, hog, etc. Each of the cooking groups brought something unique to the table, including duck tacos, crawfish eggrolls, and deer/hog gumbo. As the public got tastes of the coast, they could wander through the exhibition of restoration/protection groups. At our table we had our #ProtectOurCoast poster series and stickers, some relevant issues of WaterMarks, and activity books for our younger visitors. Visitors could also compete in Wetland Jeopardy. After learning about coastal issues and restoration efforts, visitors could enjoy more food or go into the dance hall where Michot’s Melody Makers were playing their traditional Cajun music.

As the day came to a close, everyone gathered in the dance hall to award the best dishes as decided by the public. Awards were given for the best overall dish as well as best dish in 3 categories: Crawl, Fly, and Swim. With so many good contenders, the decision must have been difficult for the voting visitors. We would like to congratulate all the participants for getting involved with such a meaningful cause and preparing such delicious food. We’d like to thank the visitors and other exhibitors, as well as the Meraux Foundation, for the opportunity to share our love of wetlands and food- we cannot restore our coast without them.

 

America Recycles And So Do We

Recycling is a great practice at home, but it reaches far beyond taking materials out of the waste stream. Tomorrow, November 15^th, is designated as America Recycles Day, so today’s Wetland Wednesday is hopeful about the future of sustainability.

New materials require exploration and processing that can be destructive to ecosystems. Plastics, some of the most common materials in the product stream today, are largely recyclable. As a crude oil byproduct, producing new usable plastics requires a lot of energy. The same goes for many other recyclable materials. Paper products, various metals, and glass all take a lot of energy to produce, then they quickly find their way into landfills instead of being reused. Landfills produce a wide array of chemicals that often leach into the ground due to poor containment practices, and they can contaminate watersheds. Once those chemicals get into a watershed, they can significantly decrease the health of wetlands across huge swaths of land over time. To further the polluting effects, drilling for oil to meet a growing desire for fossil fuels is one of the most detrimental practices to wetlands. More than 5 years after the Deepwater Horizon oil spill in the Gulf of Mexico, Louisiana wetlands continued to lose ground due to the spill’s impact. [1]

Recycling is not a perfect alternative to single-use plastics, and there are other ways to reduce our consumption of resources. For example, mitigating loss of byproducts by finding new and inventive applications can greatly reduce consequences. Large-scale food manufacturing leaves plenty of byproduct as leftover plant material that can be used as livestock feed, potentially as biofuels, or fertilizer. In the meat industry, byproducts are often further processed and commercialized to maximize the use of all parts of animals. CWPPRA and our partners have changed some practices in recent years to be more efficient when using resources, for example beneficial use of dredged material (yes, we recycled our header image). Mandatory dredging of shipping and navigational channels produces a bounty of sediment that was lost in the past, but we can now use that material in restoration projects. This exciting new practice has already been implemented in a few CWPPRA projects to restore marshland and nourish pre-existing wetlands.

Our coast faces many human-caused threats, and its future depends, in part, on practices becoming more sustainable. By using new technologies to better use resources, CWPPRA hopes that Louisiana’s natural splendor and resilience can continue to benefit future generations.

[1] https://pubs.er.usgs.gov/publication/70178409

 

Moving Land: Erosion and Sediments

Land loss and land gain are terms we throw around a lot at CWPPRA but what do they mean? Where does the old land go and where does the new land come from? To answer that, we need to understand that “land” is made of inorganic particles that we call sediment and various types of organic matter. Sand, clay, gravel, boulders, and silt are all types of sediment, and grain size is how we classify them. [1] For example, a boulder is larger than gravel, which is larger than a grain of sand, which is larger than a silt particle, etc. Sediment size influences how each grain experiences force and inertia, which leads to different rates of land loss and gain between sediments. Imagine holding a handful of sand in one hand and a handful of gravel in the other. Now imagine you blow as hard as you can on each one. More gravel would stay in your hand than sand. The same is true of sediment in water- smaller grains of sand can be picked up more easily by the forces acting on them than the gravel can.

Erosion detaches sediment from an original source, such as a cliff face or the middle of a valley. Over long periods of time, eroded particles get smaller and smaller, eventually degrading to sand or silt, depending on the mineral base. Once they get into a river or stream, their movement is connected to water flow. When water flows faster or stronger, it “suspends” and carries more sediment, while sediments in slower currents tend to settle out and “deposit” on the bottom of the lake, bayou, or swamp. Approximately 40% of the USA drains through the Mississippi River, and any suspended sediment in those waterways travels through Louisiana on its way to the Gulf of Mexico. [2]

Sediments move downstream differently depending on their size class.

Wetlands are defined by sediment type and other characteristics including salinity. In Louisiana, we have fresh water wetlands like swamps and bottomland hardwood forests, but also saline wetlands like salt and brackish marsh. Each of these wetlands types contains fine sediment particles, and they are all relatively new in the scope of geologic time. Because they are young, there are not many hard-packed substrates in Louisiana wetlands, but instead deeper layers of sediment that are compacting and subsiding. [3] Sediment replenishment is important to all the wetlands in Louisiana because new sediment is needed on top of compacting sediment to maintain elevations that support plant life and productive ecosystems. Unfortunately, sediments that should be replenishing the wetlands of Louisiana are not doing so. Instead, they are being transported out into the Gulf of Mexico or are trapped farther upstream behind dams. More information about this topic can be found in our post “The Mississippi River Deltaic Cycle”. Controlling the flow of the Mississippi river keeps sediments suspended for longer because water does not disperse or slow down as it naturally wants to. Without new sediment, marsh platforms lose structural integrity and they erode, leaving open water where marsh once was.

To answer the original question; for CWPPRA land loss is the process of sediment and marsh sinking or eroding into open water along Louisiana’s coastline and reducing the land available. Land gain describes the process of sediment depositing to form new platforms and it is much less common along our coast, but CWPPRA and their Partners in Restoration are working to restore the integrity of coastal wetlands by moving and capturing sediment, planting stabilizing species on terraces, and creating marsh in critical areas. Combating land loss is a multi-disciplinary effort, and we have a long fight ahead.

 

Featured image: http://amazonwaters.org/waters/river-types/whitewater-rivers/

Embedded image: http://blog.sustainability.colostate.edu/?q=schook

[1] https://www.tulane.edu/~sanelson/eens1110/sedrx.htm

[2] https://www.nps.gov/miss/riverfacts.htm

[3] https://www.sciencedirect.com/science/article/pii/S027277140600312X

West Fourchon Creation & Nourishment Marsh

The primary causes of land loss in the project area are oil
and gas canals, subsidence, and sediment deprivation, which
have resulted in an estimated rate of -0.41% per year based
on hyper-temporal analysis conducted by USGS for the
extended project boundary for the years 1984 to 2012.
Bounded by Bayou Lafourche to the east and Timbalier Bay
to the west the project area is also subject to shoreline
erosion.

This project would create 302 acres of saline inter-tidal marsh
and nourish 312 acres of emergent marsh using material
dredged from the Gulf of Mexico, southwest of the project
area. Earthen containment dikes will be constructed along
the project boundary to contain the material. Vegetative
plantings are planned at a 50% density, with half planned at
TY1 and half planned at TY3 if necessary. Containment
dikes will be degraded or gapped by TY3 to allow access for
estuarine organisms. Funding will be set aside for the
creation of tidal creeks if needed. This project, along with
TE-23 West Belle Pass Headland Restoration and TE-52
West Belle Pass Barrier Headland Restoration, will help
stabilize the edge of the marshes and protect Port Fourchon
from the west. The initial construction elevation is +2.4 feet
NAVD 88; after settlement, marsh is expected to be +1.4
NAVD 88.

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

This project was approved for Phase I Engineering and
Design in January 2015.

This project is on Priority Project List (PPL) 24.

The West Fourchon Creation & Nourishment Marsh sponsors include:

• Federal Sponsor: National Marine Fisheries Service
• Local Sponsor: Coastal Protection and Restoration Authority

 

East Leeville Marsh Creation and Nourishment

There is widespread historic and continued rapid land loss
within the project site and surrounding areas resulting from
subsidence, wind erosion, storms, and altered hydrology.
The wetland loss rate for is -1.53%/year based on USGS data
from 1984 to 2015. Furthermore, the limits of Southwestern
Louisiana Canal are difficult to determine in some areas
because land loss is causing the coalescence of the canal
with adjacent water bodies. Natural tidal flow and drainage
patterns which once existed are currently circumvented by
the increasing area of open water. Data suggests that from
1932 to 1990, the basin lost over 245,000 acres of marsh, and
from 1978 to 1990, Barataria Basin experienced the highest
rate of wetland loss along the entire coast.

The project goal is to create approximately 358 acres and
nourish 124 acres of saline marsh east of Leeville.
After consideration of three potential alternatives, features
and an alignment were selected to establish an arc of
wetlands along the north side of Southwestern Canal,
Lake Jesse, and the west side of South Lake. This is to
begin rebuilding the structural framework of wetlands
east of Leeville and provide protection for Leeville from
southeasterly winds and tides. A robust engineering and
design cost was included for full flexibility during Phase 1
to expand the project if cost allows or to assess alternative
configurations, if necessary. The proposed features consist of
hydraulically mining sediment from a borrow source in Little
Lake west of Leeville and pumping dredged material to
create and nourish marsh east of Leeville. The disposal areas
would be fully contained during construction and gapped
no later than three years post construction to facilitate
establishment of tidal connection and function. Additionally,
a portion of the created marsh acres would be planted with
smooth cordgrass following construction to help stabilize the
created platform by increasing the rate of colonization.

This project is located in Region 2, Barataria Basin, Lafourche Parish (primary)
Region 3, Terrebonne Basin, Lafourche Parish.

This project was approved for Phase I Engineering and
Design in January 2016.

This project is on Priority Project List (PPL) 25.

The East Leeville Marsh Creation and Nourishment’s sponsors include:

• Federal Sponsor: National Marine Fisheries Service
• Local Sponsor: Coastal Protection and Restoration Authority

WETshop 2017

On Tuesday,  June 11^th, the CWPPRA Public Outreach staff traveled to the Louisiana Department of Wildlife and Fisheries Marine Research Lab in Grand Isle, Louisiana to discuss Louisiana wetlands with teachers from around the state. The teachers participated in WETshop: a week-long, dynamic teacher workshop that allows teachers to work with educators and scientists to learn about Louisiana coastal wetlands, issues, and history. The focus of the summer workshop is to create wetland stewards of teachers in order for them to educate coworkers and students in their home parishes about coastal land loss. The workshop was sponsored by the Louisiana Department of Wildlife and Fisheries and the Barataria-Terrebonne National Estuary Program. During WETshop, the teachers get a firsthand look at the importance of wetlands through visiting coastal ecosystems, water quality testing, marsh tours of coastal restoration sites, and the opportunity to learn about fisheries management, coastal botany and ornithology, and invasive species.

The Coastal Wetlands Planning, Protection, and Restoration Act’s Public Outreach staff participated in WETshop as coastal wetland educators. CWPPRA provided each of the twenty teachers with packets containing numerous publications and teaching resources, as well as posters from CWPPRA’s #ProtectOurCoast campaign. The public outreach staff also gave a presentation that highlighted causes of land loss, benefits of wetlands, CWPPRA’s history and success with projects, the Coastwide Reference Monitoring System, and different ways teachers can access and utilize wetland teaching materials.

Visit CWPPRA’s Education page to access coastal teaching tools.

Bayou Bonfouca Marsh Creation

The marsh in this area was fairly stable prior to Hurricane
Katrina in August 2005. There was extensive damage to the
marsh along the north shore of Lake Pontchartrain and
especially localized in the marshes near Bayou Bonfouca
when the storm surge removed many acres of marsh. Marsh
loss rates should increase in the marsh surrounding these
newly created open water areas due to an increase in wind
driven fetch. Within the project area, the Lake Pontchartrain
shoreline erosion rates seem to be very low. Currently, there
is one large breach and several smaller ones in the Lake
Pontchartrain shoreline, with many more breaches seemingly
imminent. These breaches provide direct connection between
the fresher interior marshes and higher saline waters of Lake
Pontchartrain. The breaches in the bankline should be filled
before they grow to become a major exchange point causing
an increase in interior loss rates.

The primary goal of the project is to create 533 acres and
nourish 42 acres of low salinity brackish marsh in open
water areas adjacent to Bayou Bonfouca with sediment
pumped from Lake Pontchartrain.
This project would consist of placing sediment, hydraulically
dredged from Lake Pontchartrain, in open water sites to a
height of +1.2 NAVD 88 to create 458 acres and nourish
approximately 133 acres of marsh. Several historic marsh
ponds have been identified and would be restored. Tidal
creeks are also proposed to connect these ponds to facilitate
water exchange and fisheries access. Containment dikes
would be sufficiently gapped or degraded to allow for
fisheries access no later than three years post construction.

The project would result in approximately 424 net acres of
intermediate marsh over the 20-year project life.

This project is located in Region 1, Pontchartrain Basin, St.
Tammany Parish. Parts of the project are located within Big
Branch Marsh National Wildlife Refuge adjacent to Bayou
Bonfouca.

This project is on Project Priority List (PPL) 20.

The Bayou Bonfouca Marsh Creation project sponsors include:

• Federal sponsor: U.S. Fish and Wildlife Service
• Local sponsor: Coastal Protection and Restoration Authority

Keep up with this project and other CWPPRA projects on the project page.

Shell Beach South Marsh Creation

The marsh boundary separating Lake Borgne and the MRGO
has undergone both interior and shoreline wetland losses due
to subsidence, impacts related to construction and use of the
MRGO (i.e., deep draft vessel traffic), and wind-driven
waves. Although much of the project area is protected from
edge erosion by shoreline protection measures, and since
2009, the MRGO has been deauthorized for deep draft
navigation and maintenance, interior wetland loss due to
subsidence continues to cause marsh fragmentation and pond
enlargement. Wetland loss rates in the project area are
estimated to be -0.60 percent a year based on USGS
analysis.

The proposed project will create and nourish 634 acres of
marsh using dredged sediment from Lake Borgne. Existing
high shorelines along Lake Borgne, remnants of previous
containment dikes and marsh edge, would be used for
containment to the extent practical. Constructed containment
dikes would be breached/gapped as needed to provide tidal
exchange after fill materials settle and consolidate. The
project would create 346 acres of marsh and nourish at least
288 acres of existing fragmented marsh. A target fill
elevation of +1.2 feet is envisioned to enhance longevity of
this land form. Additionally, 187 acres of vegetative planting
will occur within the newly created areas. Due to the
presence of existing banklines, dredged slurry overflow
could potentially be discharged immediately adjacent to the
project polygons, resulting in nourishment of additional areas.

This project is located in Region 1, Pontchartrain Basin, South Lake Borgne Mapping
Unit, St. Bernard Parish, north bank of the Mississippi River
Gulf Outlet (MRGO) in the vicinity of Shell Beach.

This project is on Project Priority List (PPL) 24.

The Shell Beach South Marsh Creation project sponsors include:

• Federal sponsor: U.S. Army Corps of Engineers and U.S. Environmental Protection Agency
• Local sponsor: Coastal Protection and Restoration Authority

Keep up with this project and other CWPPRA projects on the project page.