4 minute read
Winfield Locks and Dam
Winfield, West Virginia, United States
Placing dredged material for mussel recruitment. Maintenance at Winfield Locks and Dam on the Kanawha River, a tributary of the Ohio River and a commercially navigable river monitored by the U.S. Army Corps of Engineers (USACE)–Huntington District, is an example of efficient and sustainable use of dredged material. The navigation channel downstream of the locks requires regular maintenance dredging due to continuous shoaling. The dredged material is placed against the opposite bank on the outside bend of the river, creating a velocity shelter that accumulates and maintains preferred substrates for mussels. Before the site was modified in the mid-2000s, the adjacent habitat was dominated by a large section of bedrock and boulders providing poor substrates for various mussel species. This nature-based velocity shelter has helped stabilize the habitat, and the material itself provides a source of clean sands and gravels that migrate downstream to provide the necessary substrates for mussel colonization. Since placement began, survey results have shown an increase in the areas covered by silt, sand, gravel, and cobble. This habitat enhancement has coincided with increases in mussel density and diversity. Because of its habitat transformation and mussel recruitment, the natural resource agency partners have requested that the district prioritize the use of the site.
Article Cover: After construction, the placement pile remains an emergent feature until higher river flows smooth it over. (Photo by USACE Huntington District)
Producing Efficiencies
The realized efficiencies are notable, especially due to the development of a velocity shed using dredged material from the adjacent navigation channel. Multiple placement efforts have shielded downstream velocities from returning substrates to the previous hard-bottom strata that prevented mussel-bed establishment. Subsequent placements have seeded the area with finer and more beneficial material. The channel’s decreased size due to the island bar creates potential for increased velocity and subsequent decreased sedimentation of material shoaled in the channel. Reducing the placement distance of dredged material also reduces transport cost, making placement at the project site the least-cost placement alternative.
Using Natural Processes
The hydrodynamic forces created on the outside bend below Winfield originally resulted in the substrates being stripped to bedrock. When paired with this dredge placement operation, these same forces are now creating sustainable mussel habitat. Five surveys from 2002 to 2023 showed a gradual change in the primary substrate near the Winfield placement area from large boulders and bedrock to areas of silt, sand, gravel, and cobble inhabited by mussels. These data indicate that the dredge placement combined with downstream dispersion of the placed sediment by the river’s energy are providing beneficial habitat to promote mussel beds. Early surveys showed only four to seven species present throughout the site, while the most recent survey found diversity had risen to 16 species of native mussels.
Broadening Benefits
Maintenance dredging creates the annual need for placement locations that are cost-efficient, environmentally acceptable, and reusable. The Winfield location demonstrates that, sometimes, dredge placement areas can benefit the local ecology. The material’s ability to stabilize and sustain a mussel resource at Winfield has initiated a search along the Kanawha River for similar locations. Local historical characterizations of dredged material placement as harmful have given way to the possibility that significant ecological benefits can come from the careful selection of placement sites. The Winfield site will benefit the continued maintenance of the navigation channel and the river’s mussel resources.
Promoting Collaboration
The district’s approach to managing dredged material to support and enhance mussel-bed habitat near the project location was substantially advanced through coordination and collaboration with various state and federal stakeholders (West Virginia Department of Natural Resources, West Virginia Department of Environmental Protection, and U.S. Fish and Wildlife Service). Each year, this group of partners discusses recent dredging operations, future plans, water-quality analyses, mussel surveys, protected species, and changing protocols. Effective communication within the group has resulted in a Water Quality Certification from the West Virginia Department of Environmental Protection and the agreement about the continued use of this placement site over others due to its positive impact on mussel habitat in the river.
