Shoreline Habitat Types and Erosion Rates on Marine Corps Base Camp Lejeune
Project Status: This project began in July, 2007 and was completed in December, 2012
We mapped shoreline habitats, determined historic erosion rates, and examined impacts from military training activities and non-military vessels on shoreline habitats and erosion rates. We used this information to help Marine Corps Base Camp Lejeune make decisions about protecting their shoreline, providing erosion forecasts, identifying areas needing restoration, and offering guidance on restoration approaches.
Why We Care
Amphibious vessel training is central to Marine Corps Base Camp Lejeune’s mission of maintaining expeditionary force readiness. Because of this, Camp Lejeune - the largest Marine base on the East Coast - is committed to sustainably managing its coastal ecosystems and shoreline. Wave energy erodes estuarine shorelines and is exacerbated by storm events. Erosion causes property loss and decreases the ecosystem services associated with shoreline habitats. Understanding the rates and causes of shoreline habitat loss will not only help Camp Lejeune improve their shoreline stabilization strategy, but will provide information other coastal communities can use to conserve and protect their estuarine shorelines.
What We Did
We mapped the entire estuarine shorelines within Camp Lejeune. Working from a small boat and using RTK GPS and GIS software, we documented the extent and types of shoreline marsh, sediment bank, swamp forest, and hardened structures in most of the New River Estuary and the Atlantic Intracoastal Waterway near the New River Inlet. We used historical aerial photography to map the estuarine shoreline location in 1956, 1989, and 2004 and calculated shoreline change rates. We also used aerial photography to examine shoreline and habitat changes associated with military training areas.
What We Found
We found that sediment banks, which represent over half of the Camp Lejeune shoreline along the New River estuary, are eroding at the fastest rate: an average rate of 0.4 m/y (3 ft/yr) between 1956 and 2009. We also found that sediment bank shorelines with a small amount of fringing marsh (< 5 m) had significantly lower erosion rates than sediment banks without any fringing marsh. About 21% of the Camp Lejeune shoreline was hardened, primarily with revetments. We also examined erosion rates along the Atlantic Intracoastal Waterway (AIWW) where it bisects the base and found that the width of the channel had doubled between 1958 and 2007, from approximately 60 m to 120 m wide. Several of the military splash points along the AIWW exhibited even higher erosion rates.
Salt marsh habitats make up 20% of the shoreline along the mainstem of the New River estuary and over 80% of the AIWW shoreline. The erosion rate for marshes in the estuary is about 0.25 m (1 ft)/yr, whereas, in the AIWW, the marsh shoreline is eroding at about 0.5m (1.5 ft)/yr. We found that the military’s landing craft air cushion (LCAC), a hovercraft capable of moving 75 tons of equipment over beach and marshes, causes comparatively little harm to the salt marsh as it moves over it. Inlet migration, storm events, and boat-wake erosion are greater threats to the salt marshes lining the AIWW.
We mapped the distribution of marsh species along the estuarine gradient, and, by combining a shore-based mapping effort with aerial photography, we were able to identify an additional 20 km (10 miles) of fringing salt marsh habitat along Camp Lejeune’s shorelines. This assessment of shoreline habitats and erosion rates supported other research at Camp Lejeune to predict the sustainability of marsh habitat to sea level increase.
We are preparing a shoreline management plan for the base that will present all the data on shoreline habitat type, stabilization structures, and erosion rates in narrative and GIS formats. The plan will also describe the distribution of marsh habitats and recommend areas for restoration and other soft erosion control methods, as well as identify splash points that may require more structural approaches to erosion control. The plan will also estimate long-term shoreline erosion rates as an aid to land-use planning and identify low-lying areas that are particularly susceptible to sea level increase and storm surge events. We will work with the USACE on developing approaches to minimize the loss of sediment from salt marsh habitat via commercial and recreational boating and AIWW maintenance dredging.
Related Region of Study: North Carolina
Primary Contact: Carolyn Currin
Related NCCOS Center: CCFHR