Deal Island Thin Layer Placement Project
The US Army Corps of Engineers, in partnership with the Maryland Department of Natural Resources (DNR), Audubon Mid-Atlantic, NOAA, and the US Fish and Wildlife Service, is organizing a thin-layer placement project that will be carried out on DNR-owned marsh just south of the Impoundment area in Dames Quarter in 2021. Thin-layer placement, or marsh enhancement, is a marsh restoration method where a layer of sediment is sprayed, or placed via pipeline, over a degraded marsh to increase elevation and shore up marsh habitat.
This project will help achieve two pressing needs. First, it will provide a site to place dredged sediments from the lower Wicomico River, which the US Army Corps of Engineers dredges on a 2-3 year cycle to maintain the federal navigation channel for the Port of Salisbury -- Maryland’s second largest commercial port. Maintaining this channel is especially important for sustaining the Eastern Shore’s economy, but finding sites for the approximately 120,000 cubic yards of dredged material that is collected each dredge cycle is often challenging. The Corps is required to contain the sediments (open water placement is not allowed in Maryland’s waters), but finding upland placement sites that are within close proximity and accessible to the dredge area is becoming increasingly difficult. Many of the upland locations that have been historically used as placement sites have been filled, and alternative sites are either too expensive due to their real estate value or are protected as tidal or nontidal wetlands. Shipping the sediment elsewhere is often very financially burdensome, which has left the Corps to pursue novel and beneficial ways to reuse the material, such as through marsh restoration opportunities.
Secondly, this project will help elevate sections of declining marshes in the Deal Island Wildlife Management Area that are beginning to fragment and drown from rising waters. One of the main goals is to support critical habitat for the saltmarsh sparrow and black rail, two species of birds whose nesting grounds in these marshes are increasingly being inundated, and whose populations are in sharp decline as a result. If the saltmarsh sparrow populations continue to decline, they risk being listed as an endangered species, which could result in major restrictions on future attempts to lift the marsh, as well as lead to additional regulations placed on landowners and hunters who use the marsh where these birds tend to nest. This project will also enhance the storm surge protection these marshes provide for the impoundment berm and potentially for communities further inland.
How does Thin-Layer Placement work?
Thin-layer placement is a relatively new practice for restoring vulnerable marsh. It is often carried out using dredged sediment, and involves spreading a layer of sediment that ranges from a couple inches to roughly two feet. The thickness of the sediment layer is determined by the site’s context (e.g. the plant species that grow there or the plant species that the project wants to plant there, the location’s elevation and environmental conditions, and type of sediment used). The sediment can be deposited using an aerial sprayer/nozzle or directly placed via hydraulic pipeline as a watered-down sediment mixture.
Thin-layer placement and other dredge reuse marsh restoration projects have been carried out in other areas of the Chesapeake Bay area with promising success, in particular in the Blackwater Wildlife Refuge. Because thin-layer placement is relatively new, researchers are still learning about its potential as a marsh restoration practice, particularly in light of future climate change impacts.
Thin-layer placement was carried out in the Blackwater Wildlife Refuge to address increased rates of marsh fragmentation attributed to rising sea-levels, erosion, and nutria damage. Over the last few decades, the Refuge has seen over 5,000 acres of wetlands convert to open water. In December 2016, The National Fish and Wildlife Service, in partnership with Audubon and The Conservation Fund, implemented a thin-layer placement project to restore 40 acres of marsh within the Refuge, using dredge material from the Blackwater River. Their goal was to expand the longevity of critical habitat for the saltmarsh sparrow. This project deposited 26,000 cubic yards of material to elevate the targeted marsh site by about 4-6 inches. Following placement, the area was replanted with marsh grass plugs to help the marsh regrow, which successfully revegetated the marsh by the fall of 2018.
On Smith Island, the Army Corps of Engineers and its partners re-used approximately 60,000 cubic yards of material dredged from local navigation channels to carry out a marsh restoration project on Swan Island, a severely eroded island located just north of Ewell. This project helped to restore 11 acres of high marsh, a half-acre of low marsh, and nearly an acre of dune on the island, providing benefits for both the community and wildlife. This project enhanced the island’s capacity to buffer residents from wind and storms and enhanced important habitat for ecologically and economically important fisheries, waterfowl, and other wildlife. The marshes were re-planted in 2019, and the project team will be monitoring the site to see how well it holds up in the future.
Many of the partners who helped carry out both the Blackwater and Swan Island projects will be involved in implementing the Deal Island Thin-Layer Placement Project.
How will the Deal Island Thin-Layer Placement Project be implemented?
The Army Corps of Engineers will build a pipeline to carry the dredge material across the Peninsula to a section of marsh just south of the Deal Island Impoundment area. This pipeline will travel from the Wicomico River up Dames Quarter Creek, passing under Route 363.
Dredged sediment will be placed via hydraulic pipeline over the selected marsh site during the fall of 2021 and early winter 2022. The dredging and placement of dredged sediment will occur simultaneously. The goal is to build up a layer of sediment that is, on average, one and a half feet above the existing marsh elevation. This is perhaps one of the trickiest parts of this project, as putting too little sediment will not raise the marsh appropriately, but adding too much will lead to the sediment becoming chemically uninhabitable to marsh vegetation. The end of the pipeline will be able to be moved around to allow for elevations to be built up as needed on different areas of the marsh within the placement site.
The Army Corps of Engineers is funding the majority of the project’s expenses, but Wicomico County, as the project’s Local Sponsor, and the Maryland DNR are also providing financial support to enhance the project’s restoration efforts. In addition, Audubon Mid-Atlantic will be funding replanting efforts through a US Fish and Wildlife Service grant that they were just awarded. This grant will also provide funding to the University of Maryland and DIPP for community engagement activities. Once project permits are approved, the project will be able to get underway.
Additional details about the implementation process are being developed and will be shared through DIPP as they become available.
What are some of the potential short-term and long-term impacts of this project?
Impacts to Rt. 363 should be minimal during the project implementation. The pipeline that the Army Corps will construct will be directionally bored under Rt. 363 from DNR land to DNR land. Road closures are unlikely, though there will be increased activity near this pipeline site and the presence of equipment.
After the dredge material is in place, the placement site will look like a large mudflat. The existing wetland grasses may push new shoots through the mud in thinner areas, but the majority of the newly raised wetland will be replanted with vegetation species preferred by saltmarsh sparrows and black rails to provide optimal habitat conditions. This will most likely take a few years for full recovery. Replanting the area with native plants -- as Audubon and the Army Corps of Engineers plans to do -- will be necessary in most areas. Plantings (of plugs for example) will not happen until the dredge material is solid enough to support weight, most likely in the summer of 2022 or beyond. Aerial application of seed may potentially be completed in the summer of 2022 to provide an intermediate cover until the desired species of marsh grass becomes established. Project partners will monitor the area closely throughout this time to ensure that invasive species do not become an issue. The site will also be monitored for sediment stabilization and habitat use, particularly by the saltmarsh sparrow and black rail. If this thin-layer placement project is successful, the Army Corps of Engineers hopes that this site can be used in the future as a recurring placement site for the Wicomico River dredged sediment.
Project partners also hope that the Deal Island Thin-Layer Placement Project will provide an opportunity to better understand the potential for using thin-layer placement elsewhere in the Chesapeake region. If all goes well, it could serve as a blueprint for re-using dredge material in a way that is cost-effective as well as ecologically beneficial.
What is DIPP’s role? How can I get involved?
Thin-layer placement has inherent co-benefits for communities as well. While the focus of this project is on enhancing local marshes for their ecological benefits, DIPP is interested in exploring how thin-layer placement can potentially be used in the future to support both ecological and human communities, thereby contributing to DIPP’s efforts to enhance the area’s socio-ecological resilience.
With support of the Maryland DNR, graduate students from the University of Maryland Marine Estuarine Environmental Science Program are conducting social science research to document stakeholder perceptions and attitudes about thin-layer placement. This research is one way that DIPP is developing some of these understandings. This research will help DIPP draw upon a range of perspectives to identify opportunities, challenges, and concerns for future thin-layer placement application on the Deal Island Peninsula. We also hope that it can be a way to shape future collaborations with Deal Island Peninsula communities.
Updated January 2021
US Army Corp of Engineers
Maryland Department of Natural Resources Wildlife and Heritage
NOAA Chesapeake Bay National Estuarine Research Reserve
US Fish and Wildlife Service
The Audubon Society Mid Atlantic
University of Maryland
Who do I contact for more information?
University of Maryland
DIPP Coordination Committee Member
Ongoing Activities & Highlights
Applications for Permit Approvals Underway
Project Awarded US Fish and Wildlife Funding (January 2021)
Human Dimensions Research (June 2020 - March 2021):
Understanding stakeholder perceptions and attitudes towards Thin Layer Placement. This research seeks to guide future collaborative work between the range of DIPP stakeholders who will be involved or affected by TLP application on the Deal Island Peninsula. Research is being carried out by three graduate students from the Marine Estuarine Environmental Science Program on contract through the University of Maryland.
Meet the Student Researchers
Taylor Gedeon is a Master’s student in the MEES Program, with a concentration on the relationship between the environment and society. Growing up next to a state park in New York, Taylor’s neighborhood was home to humans and bears alike, which led to her interest in working to resolve human-wildlife conflicts to enable both parties to coexist sustainably. For her Master’s thesis she is examining wildlife management practices in the United States and the potential to further include stakeholders in management decisions to support conservation and equitable wildlife responses. She is excited to join research with DIPP and looks forward to learning more about Deal Island’s beautiful marshes and coastal challenges from the communities experiencing them firsthand.
Andrea Miralles-Barboza is a Venezuelan-American who grew up in Miami, Florida and has spent the last 10 years in Maryland. Always living in places shaped by water and other natural resources, Andrea became interested in how environmental issues could be addressed by studying humans. She received a Bachelor of Science in Environmental Science and Policy in May 2018 at the University of Maryland where she attended an environmental field school in New Zealand that emphasized the need to collaborate with local communities when doing environmental research. She is back at the University of Maryland pursuing an M.S. in the MEES program where she researches responses to climate change displacement, looking at people and places who are vulnerable to issues of climate change such as sea level rise. In the future, she hopes to be able to contribute to developing accessible and appropriate climate change adaptation plans that consider not just environmental vulnerability, but social vulnerability as well.
Megan Munkacsy is a Master's student in the MEES program who first became interested in how the environment and people are related to each other when studying the cod fishery collapse in New England. Now, she works on issues relating to oysters and the Chesapeake Bay. For her Master's thesis, Megan will be working with SeaGrant to study policy options that manage conflict between oyster aquaculturists and recovery efforts for underwater grasses. Through the DIPP project, she is looking forward to meeting friends of the Deal Island Peninsula Partnership to learn about Deal Island and hear what people think about how marsh enhancement projects can help support local coastal resilience on the Peninsula.