The Mississippi River Deltaic Cycle

Water flows downhill naturally and, over time, will make a river change from one path to another. As sediment moved and elevations changed over the last 7 millennia, the Mississippi River has emptied into several historic delta complexes: Maringouin, Teche, St. Bernard, Lafourche, Plaquemines-Balize, and Atchafalaya. Each of the deltas built up part of Louisiana’s coast to what we see today, but now that natural process has been interrupted [1]. After the great Mississippi flood of 1927 that caused $1 billion worth of damages (almost $1 trillion in today’s dollars), the US Army Corps of Engineers built the world’s longest levee system under the Flood Control Act of 1928. The Levee system was constructed to reduce flood damages and allow for more control of the Mississippi [2].

Image 1: Historic Deltas of the Mississippi River

An unforeseen and unfavorable side effect to taming the river was that all the water is kept moving too quickly to deposit sediment, and now sediment is lost to the Gulf of Mexico rather than deposited into our coastal wetlands [3]. Our Louisiana coastline is dependent on new sediment to nourish wetland ecosystems. Without sediment delivery, there is no material for natural land gain or replenishment, which will continue to contribute to our retreating coastline. The solution is not as simple as removing the levee system, however, since so much of Louisiana is populated now, and removing the levees containing the Mississippi would displace millions of residents from their homes. Instead, CWPPRA and our partners in restoration use man-made systems to create marsh, nourish wetlands, and maintain hydrologic connectivity so that we can protect and restore Louisiana’s coast.

 

 

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

[2] https://en.wikipedia.org/wiki/Great_Mississippi_Flood_of_1927

[3] http://mississippiriverdelta.org/our-coastal-crisis/wasted-sediment/

Image 1 from https://www.nationalgeographic.org/photo/miss-delta-formation/

Featured image from https://phys.org/news/2015-04-future-mississippi-delta.html

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Bio-Engineered Oyster Reef Demonstration (LA-08)

LA-08

Purpose:

The purpose of this project is to test a new, bio-engineered, product to address rapid shoreline retreat and wetland loss along the Gulf of Mexico Shoreline in areas with soils of low load bearing capacity. For example, at Rockefeller Refuge, the direct Gulf of Mexico frontage and extremely low soil load bearing capacity (250-330psf), coupled with an average shoreline retreat of 30.9 ft/yr, present unique engineering challenges with a subsequent direct loss of emergent saline marsh.

Restoration Strategy:

The goal of this demonstration project is to evaluate the proposed technique as a cost effective technique for protecting areas of Coastal Louisiana’s Gulf of Mexico Shoreline with poor load bearing capacities.The demonstration project would consist of an Oysterbreak, approximately 1000′ long. The Oysterbreak is a light-weight, modular shore protection device that uses accumulating biomass (an oyster reef) to dissipate wave energy. The bio-engineered structure is designed to grow rapidly into an open structured oyster reef utilizing specifically designed structural components with spat attractant (agricultural byproducts) and enhanced nutrient conditions conducive to rapid oyster growth.

Required Monitoring: [1]

  • Topographic and bathymetric surveys (elevation, water levels)
  • Ground-level photography
  • Aerial photography
  • Wave attenuation (wave energy effects)
  • Oyster and Water quality monitoring

The Oysterbreak is constructed by placing modular units into an open interlocked configuration. The units are sized to be stable under storm wave conditions. The height and width of the Oysterbreak are designed to achieve a moderate initial wave energy reduction. As successive generations of encrusting organisms settle on the Oysterbreak, the structure’s ability to dissipate wave energy increases.

Location:

The project is located along the Rockefeller Wildlife Refuge Gulf of Mexico shoreline west of Joseph Harbor canal in Cameron Parish, Louisiana.

pic_LA_08

Project Effectiveness: [2]

The oysterbreaks are providing habitat for oyster settlement and the top layers of rings should be the most likely to support oyster colonies. Recommended improvements include:

  • Types of cement applications
  • Lessening the space available for coastal erosion (the gap between coast and oysterbreaks needs to reduce to prevent further erosion).
  • Crest elevation between the oysterbreaks performed well in wave attenuation and shoreline erosion
  • Increase the height of the structure to improve wave breaking potential

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Progress to Date:

The cooperative agreement between the National Marine Fisheries Service and the Louisiana Department of Natural Resources has been executed. Construction was finalized in February 2012. This project is on Priority Project List (PPL) 17.

More Information on this Project:

Further Websites Regarding Oyster Reef Restoration:

 

 

Work Cited:

[1] McGinnis and Pontiff. (pages 4-6) LA-08 2012 Operations, Maintenance, and Monitoring Plan, 30 April 2018, https://www.lacoast.gov/reports/project/4224379~1.pdf

[2] McGinnis and Pontiff. (page 22) 2014 Operations, Maintenance, and Monitoring Report for Bioengineered Oyster Reef Demonstration Project (LA-08)

 

 

Sabine Refuge Marsh Creation Cycle III

CS-28-3-01

The project area is experiencing marsh degradation due to
saltwater intrusion and freshwater loss. This has resulted
in the conversion of vegetated intermediate marsh to
large shallow open water areas. Salinity migrates into the
region from the Calcasieu River. Southerly winds push
saline waters into the project area through existing canals
and bayous. Wind driven waves cause further loss of the
remaining marsh fringe.

Cycle III consists of the creation of 232 acres of marsh
platform using material dredged from the Calcasieu River
Ship Channel. Between February 12 and March 31, 2007,
828,767 cubic yards of dredged sediment material was
placed into the Sabine Refuge Cycle III marsh creation area.
The dredged material is contained by earthen dikes. Lower
level earthen overflow weirs were constructed to assist in the
dewatering of the marsh creation disposal area and to create
fringe marsh with the overflow. The dredged slurry has been
placed between elevations 2.03 NAVD 88 to 2.71 NAVD 88.

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This project is located in the Sabine National Wildlife
Refuge, west of LA Highway 27, in large, open water areas
west of Brown’s Lake in Cameron Parish, Louisiana.

The Sabine Refuge Marsh Creation Project was originally
approved as part of the Project Priority List 8 in 1999. The
project was later broken into 5 cycles. In 2004, additional
funds for engineering and design and construction were
approved for Cycle III. The placement of the dredged
material has been completed. Degradation of the retention
dikes is ongoing and expected to be completed soon.

This project is on Priority Project List (PPL) 8.

The Sabine Refuge Marsh Creation Cycle III’s sponsors include:

Sabine Refuge Marsh Creation Cycle II

CS-28-2-01

The project area is experiencing marsh degradation due to
saltwater intrusion and freshwater loss. This has resulted
in the conversion of vegetated intermediate marsh to large
shallow open water areas. Salinity migrates into the region
from the Calcasieu River. Southeast winds push saline
waters into the project area through canals and bayous.
Wind driven waves cause further loss of the remaining marsh
fringe.

A permanent dredged material disposal pipeline, measuring
3.57 miles in length, will be constructed in Cycle II. The
pipeline will commence near Mile 13.2 of the Calcasieu
River Ship Channel and terminate at the northeastern corner
of the Sabine National Wildlife Refuge. Much of the right
of way required for the pipeline was previously impacted
by the construction of a temporary pipeline used during the
construction of Cycle I. The pipeline is to be used for future
marsh creation projects in conjunction with the U.S. Army
Corps of Engineers maintenance dredging of the Calcasieu
River Ship Channel.

map

The project is located on the
Sabine National Wildlife Refuge, west of Highway 27, in
large open water areas northeast of Brown’s Lake.

The Sabine Refuge Marsh Creation Project was originally
approved as part of the Project Priority List 8 in 1999. The
project was later broken into 5 cycles. In 2004, additional
funds for engineering and design and construction were
approved for Cycle II. The pipeline is constructed and will
be available for use during the 2011 maintenance dredging of
the Calcasieu River Ship Channel.

This project is on Priority Project List 8.

The Sabine Refuge Marsh Creation Cycle II’s sponsors include:

Non-Rock Alternative to Shoreline Protection Demonstration

LA-16-01

Several shoreline areas within coastal Louisiana consist
of unstable soil conditions, subsurface obstructions,
accessibility problems, etc., which severely limit the
alternatives of shoreline protection. The adopted standard
across the state, where conditions allow, is the use of rock
aggregate in either a revetment or foreshore installation. The
major advantages of using rock are durability, longevity,
and effectiveness. However, in areas where rock is not
conducive for use and site limitations exist, current “proven”
alternatives that provide equivalent advantages are limited.

Several “new” concepts of providing shoreline protection
have surfaced in the last couple of years. These concepts
however, have not been researched or installed due mainly
to budget limitations or the apprehension of industry,
landowners, and others to “try” an unproven product. The
intent of this demonstration project is to provide a funding
mechanism to research, install, and monitor various shoreline
protection alternatives in an area(s) of the state where
physical, logistical and environmental limitations preclude
the use of current adopted methods.

 

photo

The project is applicable statewide.

This demonstration project is currently in the planning
phase. A solicitation package is being prepared.

This project is on Project Priority List (PPL) 18.

The Non-Rock Alternative to Shoreline Protection Demonstration sponsors include:

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

LaBranche Central Marsh Creation

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Dredging of access/flotation canals for construction of I-10 resulted in increased salinity & altered hydrology that exacerbated conversion of wetland vegetation into shallow open water bodies. Land loss is estimated to be -0.543 percent/year based on USGS data from 1984 to 2011 within the extended project boundary.

The primary goal is to restore marsh that converted to shallow open water. Project implementation will result in an increase of fisheries and wildlife habitat, acreage, and diversity along with improving water quality. The proposed project will provide a protective wetland buffer to the railroad and I-10, the region’s primary westward hurricane evacuation route, and complement hurricane protection measures in the area.

The proposed solution consists of the creation of 762 acres of emergent wetlands and the nourishment of 140 acres of existing wetlands using dedicated dredging from Lake Pontchartrain. The marsh creation area will have a target elevation the same as average healthy marsh. It is proposed to place the dredge material in the target area with the use of retention dikes along the edge of the project area. If degradation of the containment dikes has not occurred naturally by Target Year 3, gapping of the dikes will be mechanically performed. Successful wetland restoration in the immediate area (PO-17 constructed in 1994) clearly demonstrates the ability for these wetlands to be restored using material from a sustainable borrow area (outlet end of Bonnet Carre Spillway). Engineering monitoring surveys of the marsh creation area and borrow area are planned as well.

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This project is located in the Pontchartrain Basin (Region 1), St. Charles Parish. It is bounded to the north by the railroad running parallel to I-10, to the west by the marsh fringe just east of Bayou LaBranche, to the south by Bayou Traverse and to the east by marsh fringe west of a pipeline canal.

This project is on Priority Project List (PPL) 21.

The LaBranche Central Marsh Creation project sponsors include:

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

Coastwide Reference Monitoring System

In 1990, the U.S. Congress enacted the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA) in response to the growing awareness of Louisiana’s land loss
crisis. CWPPRA was the first federal, statutorily mandated program with a stable source of funds dedicated exclusively to the short- and long-term restoration of the coastal wetlands of Louisiana. Between 1990 and 2016, 108 restoration projects were constructed through the CWPPRA program. These projects include diversions of freshwater and sediments to improve marsh vegetation; dredged material placement for marsh creation; shoreline protection; sediment and nutrient trapping; hydrologic restoration through outfall, marsh, and delta management; and vegetation planting on barrier islands.

The coastal protection and restoration efforts implemented through numerous CWPPRA crms_wetlandsprojects require monitoring and evaluation of project effectiveness. There is also a need to assess the cumulative effects of all projects to achieve a sustainable coastal environment. In 2003, the Louisiana Office of Coastal Protection and Restoration (now CPRA) and the U.S. Geological Survey (USGS) received approval from the CWPPRA Task Force to implement the Coastwide Reference Monitoring System (CRMS) as a mechanism to monitor and evaluate the effectiveness of CWPPRA projects at the project, region, and coastwide levels (Steyer and others, 2003). The CRMS network is currently funded through CWPPRA and provides data for a variety of user groups, including resource managers, academics, landowners, and researchers.

The effectiveness of a traditional monitoring approach using paired treatment and reference sites is limited in coastal Louisiana because of difficulty in finding comparable test sites; therefore, a multiple reference approach using aspects of hydrogeomorphic functional assessments and probabilistic sampling was adapted into the CRMS design. The CRMS approach gathers information from a suite of sites that encompass a range of ecological conditions across the coast. Trajectories of changing conditions within the reference sites can then be compared with trajectories of change within project sites. The CRMS design not only allows for monitoring and evaluating the effectiveness of each project but will also support ongoing evaluation of the cumulative effects of all CWPPRA projects throughout the coastal ecosystems of Louisiana. Simulations made by using the resampling methodology described in Steyer and others (2003) indicated that 100 randomly selected reference sites would accurately represent the true composition of coastwide vegetation at a 95 percent confidence level. However, in order to detect a 20 percent change in coastal marsh vegetation between two time periods, at least 80 percent of the time, approximately 400 reference sites were needed. Because of land rights and other technical issues, 390 sites with a fixed annual sampling design were approved and secured for CRMS data collection. These 390 CRMS sites are located within nine coastal basins and four CWPPRA regions, covering the entire Louisiana coast. Site construction and data collection began in 2005.

Because of the quantity of products and data that will be produced over the lifetime of the CRMS project, a website (http://www.lacoast.gov/crms) was designed to be a one-stop shop for CRMS information, products, and data. The ecological data available through the website are linked to the official Louisiana CPRA database – the Coastal Information Management System (CIMS), which houses all CWPPRA monitoring data, on topics such as the following: hydrology, herbaceous marsh vegetation, forested swamp vegetation, soil properties, soil accretion, and surface elevation. Data provided by the Louisiana CPRA are available for downloading at https://cims.coastal.louisiana.gov/. The basic viewer (under Mapping) on the CRMS Web site provides a user-friendly interface for viewing information on specific sampling sites, including photos, data summaries, and report cards. Analytical teams are developing mechanisms by which individual sampling sites can be assessed in relation to other sites within the same marsh type, hydrologic basin, and CWPPRA project. These multi-scale evaluations will be presented on a “Report Card” tab within the basic viewer. The CRMS program is as dynamic as the coastal habitats it monitors. The program continues to develop new products and analysis tools while providing data for model improvement and scientific research. The CRMS Web site is the current dissemination mechanism for all activities related to the program. For a beginner’s guide to retrieving CRMS data, visit https://www.lacoast.gov/new/Ed/CRMS_Manual.pdf.

crms
Reference:

Steyer, G.D., Sasser, C.E., Visser, J.M., Swensen, E.M., Nyman, J.A., and Raynie, R.C., 2003, A proposed coast-wide reference monitoring system for evaluating wetland restoration trajectories in Louisiana: Environmental Monitoring and Assessment, v. 81, p. 107–117.