Raccoon Island Shoreline Protection/ Marsh Creation (TE-48)

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The Isles Dernieres barrier island chain is experiencing some of the highest erosion rates of any coastal region in the world. Raccoon Island is experiencing shoreline retreat both gulfward and bayward, threatening one of the most productive wading bird nesting areas and shorebird habitats along the gulf coast.

An existing demonstration project on the eastern end of the island, Raccoon Island Breakwaters Demonstration project (TE-29), has proven that segmented breakwaters can significantly reduce, and perhaps even reverse, shoreline erosion rates. The primary goal of this project is to protect the Raccoon Island rookery and seabird colonies from the encroaching shoreline by: 1) reducing the rate of shoreline erosion along the western, gulfward side and 2) extending the longevity of northern backbay areas by creating 60 acres of intertidal wetlands that will serve as bird habitat. This project has been separated into two construction phases, Phase A and Phase B. Phase A includes the construction of eight additional segmented breakwaters gulfward of the island and immediately west of the existing breakwaters demonstration project and an eastern groin that will connect existing Breakwater No. 0 to the island. Phase B involves the construction of a retention dike along the northern shore to create a back bay enclosure that will be filled with sediments dredged from the bay and/or gulf, followed by vegetative plantings.

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The project is located in the Terrebonne Basin on the western-most island of the Isles Dernieres barrier island chain in Terrebonne Parish, Louisiana.

This project was selected for engineering and design funding at the January 2002 Breaux Act Task Force meeting. Construction funding for Phase A was approved in October 2004. Request for Phase B construction funding is anticipated to occur in January 2008.

This project is on Priority Project List 11.

The Sponsors include:

Federal Sponsor: NRCS

Local Sponsor: CPRA

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Classifying Wetlands Part 2

Last week’s Wetland Wednesday mentioned 3 main criteria as part of identifying a wetland (wetland hydrology, hydrophytic vegetation, and hydric soils). – Today we’ll look at how plants and soils help scientists delineate wetlands.

In the field, scientists identify and sample soils and plants as part of wetland delineation. The LSU AgCenter groups plant species based on where the plant is naturally found as seen in the table below.

indicator_2Wetland plants have adapted to flooded soils. “Obligate” plants can tolerate water at high levels or when soil saturation is a normal condition to that area. Examples of these plants include the bald cypress (Taxodium distichum), or cattail (Typha latifolia) [3].

In contrast, plants that cannot handle flooded conditions for an extended period would naturally be in the “upland” area of land (i.e. winged sumac (Rhus copallina), eastern redbud (Cercis canadensis), or panic grass (Dichanthelium sp.) [3].

People delineating wetlands focus on a project area according to aerial and soil maps along with aerial photographs [1]. Delineators then take soil samples and determine characteristics seen in hydric soils which relate to cycles of flooding and drying. – Examples of those include oxidized soils, hydrogen sulfide (rotten egg smell) and organic bodies found on plant roots. Finally, the plant and soil types are compared, tested, then matched to determine wetland boundaries for mapping and policy purposes [1].

Wetland delineation is a tool for protecting and documenting these important landscapes which contribute to a healthy and functional environment. It is important to note that wetland delineation requires much more than just plant and soil identification. CWPPRA utilizes sound science, engineering, mapping, and geo-technical surveys in the process of planning, approving, constructing, and maintaining coastal Louisiana wetland restoration projects.

Sources:

[1] Bedhun, Rebecca. 2018. “Watch and Lean Now: How To Do A Wetland Delineation”. Shoret Elliot Hendrickson Inc. Available: http://www.sehinc.com/news/watch-and-learn-now-how-do-wetland-delineation [September 9, 2018]

[2] Jon Kusler. “Common Questions: Wetland Definition, Delineation, and Mapping”. Association of State Wetland Managers, Inc. Available: https://www.aswm.org/pdf_lib/14_mapping_6_26_06.pdf [September 9, 2018]

[3] LSU Ag Center. 2018. Louisiana Plant Identification: Plant List. Available: http://www.rnr.lsu.edu/plantid/listcommon.htm [September 10, 2018]