Currin, C.; Davis, J.; Cowart Baron, L.; Malhotra, A., and Fonseca, M., 2015. Shoreline change in the New River Estuary, North Carolina: Rates and consequences.
Aerial photography was used to determine rates of shoreline change in the New River Estuary (NRE), North Carolina, from 1956 to 2004. The NRE shoreline was digitized from aerial photographs taken in 1956, 1989, and 2004, and shoreline type was determined by ground-truthing the entire shoreline by small boat in 2009. Major shoreline type categories included swamp forest (6% of total), salt marsh (21%), sediment bank (53%), and modified/hardened (19%). Ground-truthing provided additional details on relief, marsh species composition, and structure type. A point-based, end-point rate approach was used to measure shoreline change rate (SCR) at 50 m intervals for the periods 1956–89, 1989–2004, and 1956–2004. Representative wave energy (RWE) was modeled for each interval using local bathymetry and wind data. Average SCR across all shoreline types for the entire time period ranged from −2.3 to 1.0 m y−1, with a mean SCR of −0.3 m y−1. This translates to an average loss of ~13 m for any given point over the 48-year period covered by this study. The most negative average SCR (greatest erosion) occurred along unvegetated sediment bank shorelines (−0.39 m y−1). Change along marsh shorelines (−0.18 m y−1) was lower than along sediment banks, and narrow fringing marsh associated with sediment bank shorelines significantly reduced bank erosion. Modeled RWE values were positively correlated with erosion only in the highest wave-energy settings. Erosion of sediment bank shorelines provides a conservative estimate of 17,660 m3 of sediment each year to the estuary, with marsh erosion contributing up to an additional 1900 m3 y−1. Based on analysis of the sediment volume required to maintain marsh surface elevation with respect to sea level, we hypothesize that shoreline erosion plays a vital role in supporting growth and maintenance of downstream marshes.
