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.

Advertisements

Classification of Marshes

Marsh is a type of wetland that is continually flooded with water. Marshes can be found both on the coast or inland. Most of the water present is due to surface water; however, some groundwater also fills this wetland area.

Marshes can be divided into two main categories: non-tidal and tidal.

Non-tidal Marshes:

  • Most widely distributed and productive wetlands in North America
  • Occur along the boundaries of lakes, streams, rivers and ponds
  • Mostly freshwater, but some are brackish or alkaline
  • Beneath these wetlands lie highly organic soils
  • You might spot cattails, lily pads, reeds, and an array of waterfowl in this wetland
  • Alleviate flood damage and filter surface runoff

Tidal Marshes:

  • Found along protected coastlines and impacted by ocean tides
  • Present along the Gulf of Mexico
  • Some are freshwater or brackish, mostly saline
  • Provide shelter and nesting sites for migratory fowl
  • Covered by smooth cordgrass, spike grass, and salt meadow rush
  • Slow down shoreline erosion

watershed_illustration-large

Shell Beach South Marsh Creation

banner-01

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.

map

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:

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.

St. Catherine Island Marsh Creation & Shoreline Protection

banner

The landfall of Hurricane Katrina in southeast Louisiana destroyed thousands of acres of marsh and other coastal habitats in the Lake Pontchartrain basin. The hurricane weakened the Lake Pontchartrain shoreline and large areas of interior marsh habitat were either lost or damaged near Chef Menteur Pass. This area has an estimated erosion rate of 18 ft./yr. or greater. A portion of the lakeshore is protected by rock dikes (Bayou Chevee PO-22, State only project and FWS funded project). Shorelines that are not protected by rock dikes will erode back into the shallow open water areas located near the shorelines further increasing erosion rates.

This project would extend the Bayou Chevee (PO-22) rock dike along approximately 33,324 LF of weakened Lake Pontchartrain shoreline. A 6,468 LF foreshore dike and a 13,851 LF revetment totaling 20,319 LF is proposed to be built along a portion of the Bayou Savauge NWR. This would protect approximately 201 acres. This project would also create/nourish 115 acres (100 acres of marsh creation and 15 acres of marsh nourisment). That marsh would be created by filling those sites with material hydraulically dredged from the bottom of Lake Pontchartrain. A combination of healthy established marshes, bayou ridges, and constructed earthen dikes would contain that material. All constructed containment dikes would be sufficiently gapped within 3 years to allow for exchange of nutrients and estuarine organisms. This project would work synergistically with other restoration projects in the area including CWPPRA, state, and Bayou Savauge National Wildlife Refuge projects.

The goals of the project are to 1) stop shoreline erosion due
to wind generated waves along 33,324 linear feet of the Lake Pontchartrain shoreline, preserving 201 acres (166 acres of marsh and 35 acres of shallow water) and 2) create/nourish 115 acres (create 100 acres of marsh and nourish 15 acres of marsh) landward of that shoreline protection.

Service goals include the protection/creation of habitat or improvement of habitat for species of concern (LDWF), priority species (JV), and threatened and endangered species (FWS). The creation of low salinity brackish intertidal marsh habitat would be beneficial to several species that are currently on these lists, including, but not limited to Black Rail, Mottled Duck, Brown Pelican, King Rail, and Saltwater Topminnow. Helping to improve habitat, especially on Federal and State owned lands, ensures the protection of those valuable resources in perpetuity and should be a priority.

map

This project is located in Region 1, Pontchartrain Basin, Orleans Parish.

This project was approved for Phase I Engineering and Design in January 2017 and is on Priority Project List (PPL) 26.

The St. Catherine Island Marsh Creation & Shoreline Protection project sponsors include:

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

Shoreline Protection

CWPPRA Restoration Technique: Shoreline Protection

Louisiana’s shorelines are eroding at a drastic pace, some at rates up to 50 feet per year. The fertile but fragile soils found in the wetlands are susceptible to wave energy. As land is lost, water bodies merge together, which can increase wave fetch and shoreline erosion. Behind these shorelines lie communities, highways, and infrastructure that are at risk of washing away.

Various techniques to defend the coastline have been tested and applied under CWPPRA. Rock revetments, oyster reefs, concrete panels, and other fabricated materials have been constructed along otherwise unstable shorelines to abate wave energy and reduce erosion. These structures are designed to break waves, and they often trap waterborne sediments behind the structures that, over time, can become new land.

Through the course of the CWPPRA program, advancements have been made in shoreline structures that have helped maintain natural processes while providing critical protection. Such advancements have included using lighter-weight materials that require less maintenance and can be constructed on organic sediments. Other advancements include low-relief structures that are designed to trap sediments and natural breakwaters such as reefs that can self-maintain and support other ecological functions. Other natural shoreline protection measures include vegetative plantings, whose roots help secure soils and can promote accretion. These projects are implemented with consideration for minimizing impacts to the surrounding environment. Although some shoreline structures may look foreign in a natural landscape, they are necessary features that physically protect communities and hold wetlands in place by mitigating the harsh forces that move to destroy them.

11314213453_020e6d6650_z
BA-26 Barataria Bay Waterway East Side Shoreline Protection

 

CWPPRA

Are you aware of CWPPRA’s Programmatic Benefits?

  • Proven Track Record of Project Construction– Over 25 years, 210 approved projects benefiting more than 1,344 square miles (800,000 acres); 108 constructed (16 under construction).
  • Responsive– CWPPRA projects are constructed in 5 to 7 years.
  • Interagency Approach– Cost-effective projects developed by an experienced interagency team (5 Federal, 1 State agencies).
  • Community Involvement– Local governments and citizens contribute to project nominations and development.
  • Predictable Funding– Federal Sport Fish & Boating Safety Trust Fund funding to 2021 through fishing equipment taxes and small engine fuel taxes.
  • Fiscally Responsible– CWPPRA projects are cost-effective.
  • Science Based– CWPPRA’s monitoring program (Coastwide Referencing Monitoring System-CRMS). Demonstration projects “field-test” restoration techniques for future restoration project success.
  • Complementary– CWPPRA projects complement other large-scale restoration efforts (i.e., Coastal Impact Assistance Program, State Master Plan, BP DWH Oil Spill Early Restoration and the RESTORE Act).

CWPPRA has been and will continue to be the primary source of practical experience, learning, and agency expertise regarding coastal restoration in Louisiana.