We are assessing the use of various shoreline stabilization approaches. We are focusing on: 1) the impact different methods of shoreline stabilization have on ecosystem function, and 2) the effectiveness of more natural “living shoreline” approaches in place of traditional shoreline hardening methods, like vertical bulkheads or seawalls. Our ultimate goal is to protect the interests of coastal property owners, while maximizing the functional integrity of coastal ecosystems.
Why We Care
In recent decades, increased development along our nation’s estuarine shorelines has led to shoreline hardening as landowners attempt to protect their properties from coastal erosion. Estuarine shorelines are a transition zone between open water and upland regions and provide a variety of ecosystem services, including essential habitat to commercially and ecologically important species, buffering storm-driven waves, and helping protect coastal water quality.
Erosion control structures, like bulkheads (vertical walls), interrupt the critical functions of shorelines and often lead to elevated rates of erosion on the shoreward side of the structures. Living shoreline approaches, including the placement of wetland vegetation and near shore oyster reefs, may be equally beneficial for erosion control, while maintaining the connection between land and water and preserving ecosystem services.
What We Are Doing
- Assessing the Ecological Impact of Bulkheads – We compared nutrient cycling processes, wave reduction, abundance of plant and animal species, and hurricane impacts in salt marshes stabilized by bulkheads and those without stabilization structures in place.
- Incorporating Stone Sills in the Living Shoreline Approach – We investigated differences in the vegetation and soil characteristics of natural marshes and created marshes fringed by low sills of unconsolidated stone placed parallel to shore.
- Evaluation of Created Oyster Reefs as Alternative Stabilization Structures – We worked with a panel of stakeholders to design and install a demonstration “living shoreline.” This project involved the placement of oyster shell to create several reef structures along a rapidly eroding shoreline. The reefs were placed parallel to shore, just below mean high water, with salt marsh cordgrass (Spartina alterniflora) planted on the shoreward sides.
- Living Shoreline Classroom – In 2000, we constructed a living shoreline on the property of NOAA’s Center for Coastal Fisheries and Habitat Research in Beaufort, North Carolina using created oyster reef and salt marsh. This highly visible project has been used to demonstrate the living shoreline concept to coastal resource managers, real estate professionals (through National Estuarine Research Reserve Coastal Training Workshops), and college students.
What We Found
- Ecological Impacts of Bulkheads – Marshes that exist behind bulkheads support smaller populations of birds than natural marshes. Bulkheads with fringing marshes in front of them have higher surface elevations and greater wave attenuation than those without fringing marshes. Significant erosion occurred both in front of, and behind bulkheads during a hurricane event, while marshes bordered by stone sills or natural vegetation experienced a net gain of sediments.
- Stone Sills – Plant density in salt marshes created behind stone sills rapidly (< 5 years) mirrors that of nearby natural marshes. Sill and natural marshes contained similar numbers of fish and invertebrates. Initial data suggest that stone sills with gaps allowing for animal movement may present a shoreline hardening strategy that is ecologically superior to that of bulkheads.
- Oyster Reef Demonstration Site – This site was created in the spring of 2012. The reefs are still in place and are being colonized with live juvenile oysters. The planted salt marsh is growing and spreading. All indications are that the once rapid pace of shoreline retreat evidenced on this coast has diminished. The site will continue to be monitored regularly in the coming years.
- Living Shoreline Classroom – The creation of this shoreline on the campus of NOAA’s Center for Coastal Fisheries and Habitat Research in Beaufort, North Carolina has turned a quickly eroding beach into a vibrant salt marsh populated by fish, shorebirds, and bivalves. The shoreline survived a direct impact from Hurricane Irene in 2011, and has been a valuable resource for demonstrating the living shoreline approach. It has further served as a valuable tool for teaching field methods to NOAA summer interns.
We continue monitoring changes in vegetation and elevation of created marshes and evaluating the long-term performance of these marshes relative to that of nearby natural marshes.