Wetland Restoration Planting Project
Plant Identification in Bayou Bienvenue Wetland Triangle 2010
With Wetland Scientist Dr. Quentin Carpenter
In the wake of Hurricanes Rita and Katrina many of the southeastern Louisiana levees that were exposed to open water failed, while those that were protected by intact wetlands remained undamaged (Day, 2006). With this in mind, the Army Corps of Engineers has been tasked by congress to restore the damage to the Central Wetlands Unit (which includes the Bayou Bienvenue) caused by the building of the Mississippi River Gulf Outlet (MRGO), which has been closed in 2010.
Louisiana’s wetlands provide a range of ecosystem services to the community. Wetlands historically have provided protection from storm surges, provided habitat for a 2.6 billion dollar commercial fishing industry, and supported a 1.6 billion dollar recreational fishing industry. In addition, wetlands have provided habitat for over five million migrating waterfowl as well as providing water purification services (Louisiana State University Agricultural Center, 1998) .
The Bayou Bienvenue Wetland Triangle (BBTW) has been an area of study for the University of Wisconsin for the past four years. This 427 acre degraded cypress swamp is the result of sixty years of saltwater intrusion and diversion of sediment caused in large part by the construction of commercial canals. Recognizing the need for baseline data to begin the process of restoration, the University of Wisconsin students have been cataloging water and sediment characteristics to clarify a feasible restoration project. Water depths and tidal fluctuations currently limit the types of vegetation that will thrive in the BBWT. Both in filling of the triangle with sediments and active vegetation management will be needed to restore any substantial vegetative community.
Creating a brackish marsh in the BBWT is a logical phase-one wetland restoration project. Brackish marsh plants can aid in land accretion by building biomass and trapping sediments. In addition, brackish marsh can help buffer storm surge, provide aquatic and terrestrial habitat and foster biodiversity. (UW-NOLA Report, 2009)
Our plant search was narrowed to species that are native to brackish or salt-water marshes of southern Louisiana, which exhibit a high range of salt tolerance, ability to grow in anoxic conditions and adaptability to a range of soil textures. In addition we considered a number of physiologic and morphologic characteristics such as mature height, growth rate, vegetative spread rate, and root morphology to gauge biomass production both in the soil (to hold sediment) and above the soil (to mitigate wind energy). Based on these characteristics, three species candidates were chosen for use on the floating platforms: spartina alterniflora (smooth cordgrass), schoenoplectus californicus (California bulrush) and spartina patens. (UW-NOLA group report, 2009)
View of Plantings from the Florida Street Platform
Plants on L1 include: Deerpea, Spartina patiens, Smart Weed, Poke weed, Ararantha, Spartina Alterneflora, Echinochbra
The city of New Orleans donated five islands in 2009. We inventoried these islands and found the following plants.
City Island 1
Pokeweed, Iva, Purslane, Cyperus
City planting island 2
Plants on C2 included:
Vigna luteola (Hairypod cowpea) Native to ponds and rivers
Lythrum lineare (Wand Loosestrife), spartina patens, and one unknown plant (below).
(if anyone can identify this species please post the name in the comments section of the blog)
City island plantings 3
This island contained: spartina patens, a large southern amaranth, and an unknown plant (below right)
City planting island 4
This island was one of the scarcest islands and contained: spartina patens,Iva frutescens (Marsh elder), and Amaranthus australis (Southern amaranth).
City planting island C5
Plants include: spartina patens, Ivy
Fruteschens, and Tropical flatsedge
University Island L2
In the foreground you see the thick algae that blankets the marsh at this time of year. Algae is the result of too many nutrients and is a sign of a distressed ecosystem. This island is also very diverse and includes the following plants:
Schoenoplectus maritimus (Cosmopolitan bulrush) Thick tall dark green grasses
Spartina patens (Couch grass) thin light green grasses
Echinochloa crus-galli (Barnyard grass) Light green in foreground with seed head
Dead Cypress tree (Taxodium distichum) in background-killed by excess salinity introduced into the bayou from canal development.
Amaranthus australis (Southern amaranth) We were seeing to five foot plants on the floating islands. The plant has a reddish stem and is an annual which planted itself!
Cyperus surinamensis (Tropical flatsedge) Lighter green grass in foreground
This year our job was to inventory all of the islands and determine which plantings had survived as well as inventory any new plants. Too augment the sparse plants on the city islands (C1-C5) we added more spartina patens, irises, and native marsh plants that we collected from the shorelines.
Half of the class made up the planting team (Quentin, Ted, Linda, Kelly, Jenna, Michelle) and half of the class went out to test this years water quality at points around the triangle (CeCe, Jennifer, Natalie, Ashley, and Patrick).
Behind the canoe you see the rusted metal floodwall built in the 1960′s to prevent flooding of the lower ninth ward. Unfortunately this eight foot wall made it very difficult for residents of the lower ninth neighborhood to access the swamp where they had fished for crawfish, crab, and a variety of freshwater fish. In 2008, the University of Colorado built an access platform to allow visitors and residents to once again be able to visit the bayou.