We are developing a framework and process for matching dredging needs with opportunities for beneficial use of the sediment at local marshes, to help marshes keep up with sea level rise, while continuing to deliver ecosystem services to their region. The project will focus on marshes in both Beaufort (NC) and Jacksonville (FL).
Why We Care
Coastal marshes provide numerous societal services including habitat provision, improvement of water quality, and protection of built infrastructure from storms. Intertidal marshes grow vertically by trapping sediments carried in tidal waters and an adequate sediment supply is critical for marshes to increase elevation at a rate commensurate with local relative sea level rise (SLR). Marshes will need more sediment to keep up with accelerated SLR. Dredging of navigation channels exacerbates the problem because in most cases, dredged sediments are removed from the estuarine system and disposed in either upland or offshore open-water sites. There is increasing recognition of the value of keeping dredged sediments in their local system and using them to create or enhance Natural and Nature Based Features (NNBF), such as thin-layer placement to salt marshes. Also termed beneficial use, this strategy of repurposing dredged sediments within the estuarine ecosystem can be an effective way to build marsh resilience to storms, SLR, and erosion, thereby protecting the services they provide.
What We Are Doing
The project team will develop and demonstrate a comprehensive approach for maximizing the beneficial reuse of dredged sediments within their watershed of origin, at two different study sites in Beaufort, North Carolina and Jacksonville, Florida. In particular, the focus is on thin-layer placement of dredged sediments to marshes vulnerable to SLR, and where appropriate, co-placement of living shorelines. Opportunities will be identified with regional stakeholders, and the process facilitated to synchronize maintenance dredging activities with NNBF restoration/creation projects. Engagement with local and regional stakeholders, and the regulatory community, is critical to identifying NNBF projects and the engagement will be maintained through the life of the project. Developing a framework for this process will facilitate beneficial reuse of dredged sediments into long-term planning for marsh resilience. The project team will:
- identify dredged sediment sources and placement sites with regional stakeholders;
- assess marsh vulnerability and sediment requirements using existing models (SLAMM, MEM, VIMS Geospatial Marsh Model);
- prioritize sediment placement options based on the best sites identified;
- assess protective and ecosystems services of possible restoration projects; and,
- finalize conceptual designs and information to streamline the permitting process and enable project execution by stakeholders.
Benefits of Our Work
Lessons learned from stakeholder meetings, model assessment, design team, and regulatory feedback over the three years of executing this project will be captured and shared with broader coastal communities of managers and scientists. Framework and guidance packages that describe the steps required to develop and design beneficial reuse of dredged sediments will be created. Uniting disparate stakeholders around the common theme of sediment will be the focus for project workshops and webinars. This is a proof of concept approach that is designed to lead to restoration projects in NC and FL, whereby lessons learned can be transferred to other marshes and dredging activities in the southeastern region.
The project is led by the University of North Carolina Chapel Hill and includes co-investigators from the National Centers for Coastal Ocean Science, The United States Army Corps of Engineers and EA Engineering, Science and Technology. The project is funded through the NCCOS Effects of Sea Level Rise Program.