Little Vermilion Bay Sediment Trapping (TV-12)

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High winds and waves prevent GIWW sediments transported down the Freshwater and Schooner bayous from settling and forming the basis of vegetated marsh. This same wind and wave energy also increases shoreline erosion rates.

This project involved the construction of a series of vegetated terraces to diminish waves in Little Vermilion Bay, helping to increase sediment deposition and reduce the rate of shoreline erosion. A pattern of channels was dredged 100-feet wide and 6-feet deep to beneficially distribute sediment from the GIWW through the Freshwater and Schooner bayous. Dredged sediments were used to construct 23 earthen terraces with a combined length of 23,300 feet. After settling, the average height of the terraces was 3.5 feet above mean sea level.

The bases of the terraces were planted with 20,450 containers of smooth cordgrass (Spartina alterniflora).

The design allows commercial and recreational fisherman to access the project area, and it stimulates fishery production by creating new habitat and increasing shoreline length.

In 1998 alone (prior to the project’s completion) 40 acres of wetland habitat were created.

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This project is located in the northwestern corner of Little Vermilion Bay at its intersection with the Gulf Intracoastal Waterway (GIWW) in Vermilion Parish, Louisiana. The project area encompasses 964 acres.

Monitoring is underway and preliminary observations show that the terraces are growing in width, and bay depth between terraces is decreasing indicating marsh expansion in the project area.

This project is on Priority Project List 5.

The Federal Sponsor is NOAA NMFS

The Local Sponsor is CPRA

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Goose Point/Point Platte Marsh Creation (PO-33)

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Interior ponding and, to a lesser extent, shoreline erosion are the major causes of wetland loss in the project area. Loss rates were highest during the period from 1956 to 1978. Those high loss rates were associated with hydrologic alterations which allowed salt water to penetrate the fresher marshes. During the transition to a more brackish plant community, large ponds were formed. A narrow strip of land separates those ponds from Lake Pontchartrain. Although the shoreline erosion rates are relatively low, the shoreline is already breached in several areas, and marsh loss in the interior ponds is expected to increase if the shoreline fails.

The goal of this project is to re-create marsh habitat in the open water behind the shoreline. This new marsh will maintain the lake-rim function along this section of the north shore of Lake Pontchartrain by preventing the formation of breaches into interior ponds.

Sediment will be dredged from Lake Pontchartrain and contained in cells within the interior ponds to create approximately 417 acres of marsh. In addition, 149 acres of degraded marsh will be nourished with dredged material. Marsh will be created to widen the shoreline so that the ponds will not be breached during the course of normal shoreline retreat.

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The project is located on the north shore of Lake Pontchartrain between Fountainebleu State Park and Louisiana Highway 11 and within the Big Branch Marsh National Wildlife Refuge in St. Tammany Parish, Louisiana. The project area at Goose Point also includes a portion of the St. Tammany State Wildlife Refuge.

On February 12, 2009, a final inspection of the project site was conducted. All construction activities are complete.

This project is on Priority Project List 13.

 

Federal Sponsor: USFWS

Local Sponsor: CPRA

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

Bayou Dupont Sediment Delivery – Marsh Creation and Terracing

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Wetlands in the Barataria Basin were historically nourished
by the fresh water, sediment and nutrients delivered by
the Mississippi River and its many distributary channels.
These sediment and nutrient inputs ceased following the
creation of levees along the lower river for flood control and
navigation. In addition, the construction of numerous oil and
gas canals along with subsurface oil and gas withdrawal has
exacerbated wetland loss in the area. From 1932 to 1990, the
Barataria Basin lost over 245,000 acres of marsh. From 1978
to 1990, the area experienced the highest rate of wetland loss
in coastal Louisiana.

The primary goal of this project is to create and nourish
approximately 144 acres of emergent intermediate marsh
using sediment from the Mississippi River, and constructing
9,679 linear feet of terraces. The proposed project includes
dredging sediment from the Mississippi River for marsh
creation by pumping the sediment via pipeline into an area of
open water and broken marsh. The proximity of the project
to the Mississippi River provides a prime opportunity to
utilize this renewable river sediment resource. The strategy
includes utilizing the access route and infrastructure
previously put into place for the BA-39 project. This project
will complement existing restoration projects in the area.

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CWPPRA Region 2, Barataria Basin, Jefferson and
Plaquemines Parishes. The general project area is about 10
miles south of Belle Chasse, LA and is west of LA Hwy
23 and north of the Myrtle Grove Marina. The project
is immediately adjacent to the completed CWPPRA
Mississippi River Sediment Delivery System – Bayou
Dupont (BA-39) project.

The project was approved for engineering and design at the
January 24, 2013 Task Force meeting. The E&D was
completed in the fall of 2014 and sponsors requested phase
2 funding at the January 22, 2015 Task Force meeting,
however, there was insufficient money available to fund
the entire project. In order to take advantage of the existing
mobilization of the Long Distance Sediment Pipeline
(LDSP) Project, the sponsors proposed to reduce the scope
of the project to fit within the available CWPPRA funding.
The Task Force approved the reduced scope Phase 2 funding
request at the May 14, 2015, Task Force meeting. The asbuilt
project features include 144 acres of marsh creation and
9,679 linear feet of terracing.

In addition, CPRA increased the marsh creation feature of
the project by utilizing contingency funding left over from
BA-43, thereby increasing the total marsh creation in the
area to an estimated 296 acres. Construction started in April
2016, and marsh creation was completed in November
2016. Terracing was completed in June 2017, and vegetative
plantings for the terraces are scheduled for the spring of
2018.

This project is on Priority Project List (PPL) 22.

The Bayou Dupont Sediment Delivery – Marsh Creation and Terracing sponsors include:

 

Fritchie Marsh Creation and Terracing

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A significant portion of the Fritchie Marsh was lost due to
Hurricane Katrina. Post storm shallow open water areas
dominate the landscape which limits the effectiveness of the
PO-06 CWPRRA project. Wetlands in the project vicinity
are being lost at the rate -1.09%/year based on USGS
data from 1985 to 2015. These marshes cannot recover
without replacement of lost sediment, which is critical if the
northshore marshes are to be sustained.

Project goals include restoring and nourishing marsh.
Specific goals of the project are: 1) create approximately 291
acres of marsh; 2) nourish approximately 49 acres of existing
marsh; and 3) construct about 36,610 feet of earthen terraces
or 26 emergent acres.

An alternative analysis was conducted leading to the
selection of features and configuration to compliment and
work synergistically with the existing PO-06 project and
planned mitigation and restoration projects in the Fritchie
Marsh. A robust engineering cost is included to evaluate
increasing the project size if costs allow or adjust the
layout, if needed during Phase 1. Approximately 2 million
cubic yards of material would be placed confined to restore
291 acres and nourish approximately 49 acres of brackish
marsh. Material would be dredged from a borrow site in
Lake Pontchartrain. The borrow site would be designed to
avoid and minimize impacts to aquatic habitat and existing
shorelines. Approximately 26 acres of earthen terraces would
be constructed within various locations totaling approximately
36,610 feet or 523 acres of terrace field. All containment
dikes would be gapped or degraded no later than three years
after construction to facilitate the development of tidal marsh
functions supportive of estuarine species. The terraces would
be planted as well as 50% of the created marsh acres to
expedite colonization and enhance stabilization.

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Region 1, Pontchartrain Basin, St. Tammany Parish, located
approximately three miles southeast of Slidell, Louisiana. A
substantial portion of the project is located on Big Branch
National Wildlife Refuge.

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

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

The Fritchie Marsh Creation and Terracing sponsors include:

 

Cole’s Bayou Marsh Restoration

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Project area wetlands are undergoing loss at -0.42 %/year
based on 1983 to 2011 USGS data from the extended
boundary. Wetland loss processes in this area include
subsidence/sediment deficit, interior ponding and pond
enlargement, and storm impacts resulting in rapid episodic
losses. In addition, significant interior marsh loss has
resulted from salt water intrusion and hydrologic changes
associated with increasing tidal influence. As hydrology in
this area has been modified, habitats have shifted to more of
a floatant marsh type, resulting in increased susceptibility to
tidal energy and storm damages. Habitat shifts and
hydrologic stress reduce marsh productivity, a critical
component of vertical accretion in wetlands.

The specific goals of the project are: 1) create 365 acres of
brackish marsh in recently formed shallow open water; 2)
nourish 53 acres of existing brackish marsh; and, 3) increase
freshwater and sediment inflow into interior wetlands by
improving project area hydrology.

This project aims to create 365 acres and nourish 53 acres of
brackish marsh via dedicated dredging with borrow from
nearby Vermilion Bay. Although Vermilion Bay is not
considered an “external” source of material, significant
sediment inflows into this area may result in some borrow
area infilling. Half of the marsh creation acres would be
planted. The project will encourage additional freshwater
nutrient and sediment inflow from Freshwater Bayou Canal
by dredging a portion of Cole’s Bayou along with the
installation of a series of culverts throughout the project
area.

The culverts located along the northern project boundary are
envisioned to allow the ingress of sediment, water, and
fisheries organisms into the semi-impounded project area,
but avoid backflow of water and potential loss of interior
marsh sediment (i.e., north to south flow only). The culverts
located along the southern project boundary are envisioned
to allow water to drain out of the marsh.

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This project is located in Region 3, Teche/Vermilion Basin,
Vermilion Parish, east of Freshwater Bayou Canal.

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

The Cole’s Bayou Marsh Restoration sponsors include:

 

East Leeville Marsh Creation and Nourishment

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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.

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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: