Research Projects
Previous Projects
The NCNERR contributed to a national-level research project focusing on using relatively undisturbed tidal wetland sites at or near five National Estuarine Research Reserves as reference sites for comparison with 17 local wetland restoration projects in various stages of project completion and succession.
Objectives
The study, which was funded by the NOAA Restoration Center, was guided by four main objectives:
- Determine the level of restoration achieved at each project restoration site
- Identify key biotic (vegetation) and abiotic (hydrology, soils, marsh elevation) indicators that best explain variation in restoration response
- Determine the utility of long-term wetland monitoring sites at Reserves as reference sites for restoration projects implemented within the region
- Compare responses of hydrologic and excavation/fill types of restoration
Key Findings
Each study area was monitored from 2008-2010 and evaluated using the Restoration Performance Index (RPI) to compare user-selected variables among Reserve tidal wetlands and restored tidal wetlands. Key findings and recommendations from this project included:
- Reserve tidal wetland sites can provide appropriate long-term reference sites for local tidal wetland restoration projects.
- A recently formalized ecological index, the RPI, which compares change in user-selected indicator variables over time between reference and restoration sites, offers promise as an effective trajectory analysis strategy for measuring restoration status.
- According to RPI values, most restoration projects surveyed in this study appeared to have achieved an intermediate level of restoration with two sites appearing to have become very similar to their paired reference sites, suggesting a high level of restoration.
- Two abiotic variables – 1) elevation of marsh platform, and 2) depth to groundwater were significantly correlated with plant community structure, providing important indicators of tidal wetland restoration performance.
Final NERRS Report
Why is estuarine shoreline stabilization important to our coast?
Estuarine shoreline erosion and coastal population growth have combined to make estuarine shoreline stabilization an important coastal management issue in North Carolina. Different types of stabilization structures have potentially varied impacts on the state's estuarine shoreline and the ecological benefits they provide.
Natural shorelines capture nutrients and sediment from stormwater before it enters our estuarine systems. They also provide feeding and nursery habitat for a multitude of species and dampen wave energy along the shoreline. Shoreline stabilization often leads to a change in these ecosystem services, especially when scaled to reflect growing coastal development. Bulkheads are currently the most commonly used method of shoreline stabilization in North Carolina. As understanding of ecosystem function has increased, new alternatives to bulkheads have emerged. These alternatives are designed to provide similar levels of shoreline stabilization while minimizing the reduction in ecosystem services compared to a bulkhead. The rock sill with marsh plantings is commonly referred to as a marsh sill.
What is a Marsh Sill?
Marsh sills are shore-parallel structures made up of two critical elements:
- An offshore low relief mound made of rock or oyster shell called a sill
- An intertidal area between the offshore sill and the upland containing emergent marsh vegetation
While marsh sills are considered "living shorelines" that maintain as many natural habitat elements as appropriate for the construction site, there is also concern that marsh sill construction can alter habitat types and may create new uplands that convert public land into private land.
Evaluation Project
Given the potential opportunities and challenges with using marsh sills for estuarine shoreline stabilization, as well as the 50+ expected lifetime of most marsh sill projects, the N.C. Division of Coastal Management (DCM) was tasked with evaluating how current marsh sill projects are performing.
Researchers from DCM and the N.C. Coastal Reserve undertook a qualitative technical assessment of 27 existing marsh sills located throughout the state. Sills were evaluated on two criteria:
- Are the marsh sills performing their function as expected?
- What are the landowner and adjacent property owners’ (where marsh sills
are located) perceptions of the marsh sill shoreline stabilization option?
The Division's efforts, together with simultaneous living shoreline research being conducted in the region, help provide qualitative and quantitative information regarding how marsh sills are performing in North Carolina and how they relate to larger estuarine systems and associated ecosystem services.
Final Report: N.C. Division of Coastal Management Assessment of 27 Marsh Sills in North Carolina
Bulkheads are the predominant shoreline stabilization method used in North Carolina along estuarine shorelines. However, bulkheads have the potential to cause deleterious impacts to coastal marshes that provide many useful ecosystem services. While there are alternatives to bulkheads that provide similar levels of erosion protection and minimize the impacts to coastal marshes, in North Carolina these alternatives are underutilized by estuarine property owners and marine contractors.
Research Approach
From 2008-2012, the Sustainable Estuarine Shoreline Stabilization project utilized a three-part approach to address the critical coastal management issue of sustainable shoreline stabilization in North Carolina:
- Conduct field-based research designed to quantify the impacts bulkheads have on the ecosystem services provided by the coastal marshes
- Constructions of a demonstration project utilizing a living shoreline design (alternative to a bulkhead) to stabilize an eroding shoreline
- Dissemination of project results to the general public (coastal landowners, marine contractors, students and teachers) and natural resource managers
Key Findings
The project resulted in several key findings about shoreline stabilization impacts on marsh habitat and barriers to implementing alternatives to bulkheads:
- Bulkhead sites with no fringing marsh were at least 0.5 m lower in elevation than sites with marsh.
- Fringing marshes in front of bulkheads provided effective wave attenuation during storm events, whereas wave energy at unvegetated bulkheads is equal to or higher than incident wave energy.
- Denitrification (N removal via microbial activity) scales with marsh area, so that wider marshes provide greater N removal.
- Infauna distribution patterns were extremely variable by site, year, and region; but wider marshes had taxa more characteristic of well-established, interior marshes and narrow marshes and unvegetated sites were characterized by opportunistic species.
- Bulkheaded sites, with and without marsh, supported a lower abundance of birds compared to natural marshes. Bulkheads without marsh had much lower bird diversity and numbers.
- Marsh nekton abundance increases with increasing marsh width.
- Small narrow marshes in front of bulkheads provided a higher level of ecosystem services than expected, per unit area.
- Both waterfront property owners and marine contractors desired outreach materials be available online.
- Based on monitoring to date, shoreline stabilization using oyster reef with marsh plantings is a viable, cost-effective alternative to vertical bulkheads.
- Longer-term evaluation of elevation and vegetation is needed to determine the impact of bulkheads on fringing marsh sustainability.
Final Reports and Products
For more information, read the final report: Sustainable Estuarine Shoreline Stabilization: Research, Education and Public Policy in North Carolina
Are you an estuarine property owner in North Carolina? The Weighing Your Options handbook provides information on protecting your property from shoreline erosion.
Living Shorelines Demonstration Site
Bulkheads are the most commonly used estuarine shoreline stabilization method in North Carolina, but could have deleterious impacts on the marsh habitats where they are being constructed. Potential impacts of bulkheads on marsh ecosystems include cutting off the upland from the intertidal/subtidal region, blocking coastal marsh from transgressing upland, reflecting wave energy to potentially cause increased erosion and sediment scour, and transforming gently sloping shorelines to areas with steep transitions. In addition to quantifying the impact of bulkheads on surrounding estuarine environments, in 2012 researchers from the NCNERR, NOAA, and the University of North Carolina Chapel Hill's Institute of Marine Sciences (UNC-IMS) also worked to construct a demonstration project utilizing a living shoreline design to stabilize an eroding estuarine shoreline. Living shorelines are an alternative to bulkheads and other traditional methods of estuarine shoreline stabilization, and involves natural construction materials and a design that minimizes the potential impact on estuarine ecosystem services and functions. The living shoreline demonstration project provides new data about the effectiveness of living shoreline design and construction techniques, and serves as a visual example as to how shoreline stabilization can be designed to preserve natural habitats and ecosystem functions.
The living shoreline demonstration designed for the Sustainable Estuarine Shorelines project is a novel approach because it uses loose oyster shells rather than hard structures such as bagged oyster shells, coir logs, and granite or wooden breakwaters. This allows the stabilization structure to adapt to changing conditions. The living shoreline demonstration project is constructed with all natural materials, and closely mimics a natural oyster reef, providing similar habitat and ecosystem functions to those found in a natural setting. The demonstration project was constructed on the Rachel Carson Reserve, part of the N.C. National Estuarine Research Reserve, and can be conveniently viewed by coastal decision-makers, developers and contractors, and the public. The collaborative institutional effort demonstrates a sustainable alternative to traditional bulkhead stabilization, and will continue to generate data and research products focusing on the effectiveness of living shoreline stabilization in estuarine environments.
The loose oyster shell that was deposited in 2012 has transformed into a live oyster reef, but the marsh landward of the reef has struggled to thrive. On two different occasions volunteers have planted smooth cordgrass at the site, once in 2014 and again in 2015.
Related Publications
- Information for property owners about using living shoreline techniques to stabilize an estuarine shoreline is available in the Weighing Your Options handbook.
- Digital Elevation Modeling by NOAA researchers shows how living shoreline changes over time
Why is oyster-reef restoration important in North Carolina?
Oyster reefs were once common along the North Carolina coast, but have declined significantly in recent decades. Oyster-reef restoration has become a primary way to re-establish oysters in estuarine areas, but often restoration efforts are not as successful as they could be and rigorous benchmarks of success are not always defined. As investment in restoration becomes more costly, it is important to select optimal locations for reefs that maximize their productivity and longevity to obtain the maximum possible "bang for the restoration buck".
Project Objectives
Researchers from the NCNERR and the University of North Carolina Institute of Marine Sciences (UNC-IMS) received a grant from the North Carolina Sea Grant program for a project to quantify the structural evolution of oyster reefs to guide restoration efforts. The project will provide critical information about oyster-reef growth that is necessary for predicting the sustainability of the fishery, as well as the ecosystem services the reef structure provides in rapidly changing coastal environments. This research has three primary objectives:
- Provide benchmarks of reef growth (in vertical and horizontal dimensions)
- Guide restoration projects toward areas where oyster-reef growth is deemed highest
- Provide an accurate measure of oyster-reef sustainability to increased rates of sea-level rise