4 minute read
Beneficial Use Site 4A Vegetation Workshop
Chocolate Bayou Channel, Brazoria County, Texas, United States
In 2012, a long-term management plan was implemented by the U.S. Army Corps of Engineers (USACE) Galveston District (SWG) to beneficially utilize dredged material from the Chocolate Bayou Channel on a periodic basis over a twenty-year timeframe. The beneficial use project would create and augment approximately 560 acres of marsh and bird-nesting habitat within the Chocolate Bayou Channel. As a complement to this beneficial use of dredged material effort, certain features were applied to enhance engineering objectives while maximizing environmental benefits. The containment dike was reinforced with a combination of Reef Balls and articulating concrete mattresses, and vegetation was added to work synergistically with the other two elements to prevent the dike from eroding. The dike over time self-recruited vegetation through succession, but eventually areas lacking or sparse in vegetation experienced severe erosion, compromising the integrity of the dike. In 2017, the U.S. Army Engineer Research and Development Center (ERDC) repaired the areas where vegetation had not taken hold, again using natural materials—this time, native plant species and coir materials.
Article cover: Recently vegetated portion of the dike showing saltmarsh cordgrass immediately after planting activity. (Photos by ERDC)
Producing Efficiencies
Due to the wave-attenuating properties of the native plant communities, the erosive forces on the dike were diminished, preventing costly future repairs. Three-foot-diameter Reef Balls were designed and fabricated with a special kind of concrete to replicate and attract creation of natural oyster reef; they were used, along with articulating concrete mattresses, to reinforce the dike.
Using Natural Processes
Reef Balls at Beneficial Use Site 4A have self-recruited oysters, adding natural stability and resilience to the dike. Articulating concrete blocks allowed for vegetation establishment and oyster colonization in between the interstices. Plant species act as an erosion protection mechanism by attenuating waves and binding soil particles. Desirable plant species (coral bean, desert saltgrass, yaupon holly, seashore paspalum, and Carolina wolfberry) are able to propagate to inhibit invasive undesirable plant species (sea myrtle).
Broadening Benefits
The creation of Beneficial Use Site 4A provided a cost-acceptable placement option for locally dredged material. Environmental benefits include habitat enhancement for the sooty tern and interior least tern, which are known to utilize the project site for wintering and nesting activities, respectively. Socio-economic benefits include the attraction of birdwatchers into the area. In addition, the 2017 effort was conducted as part of a workshop offered to an interagency group. The workshop provided attendees with a hands-on experience in novel planting techniques as well as perspectives and instructions for incorporating Engineering With Nature principles into coastal projects. The workshop trained engineers, scientists, and project managers in new techniques to manage dredged material placement areas using native vegetation. Workshop participants gained experience in harvesting, planting, transplanting, plugging, soil modification, coir log installation, and broadcast seeding techniques.
Promoting Collaboration
The USACE SWG and Texas Park and Wildlife Department (TPWD) implemented the 2012 effort, with the USACE SWG conducting the reef-ball deployment and the TPWD seeding the vegetation, which subsequently self-established. In preparation for the 2017 workshop planting activity, the ERDC project team consulted with local, state, and federal agencies (National Oceanic and Atmospheric Administration, National Marine Fisheries Service, U.S. Fish and Wildlife Service, TPWD, Texas General Land Office), and the Natural Resources Conservation Service via teleconferences and a series of meetings to obtain their input on mutually beneficial planting options and to comply with regulatory requirements.
