Potential Geomorphic Consequences of Wave Climate Alterations along Cuspate Coastlines

While much attention has been given to the effects of sea level rise on coastal environments, changes in wave climate (in response to predicted increases in tropical storm intensity) may also significantly impact coastal areas in the future. Characterized by rapid alongshore shifts in shoreline orientation, cuspate coastlines are particularly sensitive to changes in wave climate and thus represent the best type of coastline for detecting initial responses to changing wave conditions. Previous work indicates that Cape Hatteras and Cape Lookout, NC have become increasingly asymmetric in response to an increase in Atlantic summer wave heights identified by Komar and Allen (2007). Here, we contrast historic and recent patterns of erosion and accretion for areas surrounding Cape Fear, NC and Fishing Point, VA to determine if a similar coastline response can be detected for a location heavily impacted by shoreline stabilization efforts and a location experiencing a less-pronounced trend of increasing wave energy, respectively. We obtained shorelines from NOAA, the USGS, and the North Carolina Department of Natural Resources and used the Digital Shoreline Analysis System (DSAS) to calculate shoreline change rates for historic (pre-1975) and recent (post-1975) time periods. The 1975 breakpoint was chosen to correspond with the timing of reported increases in hurricane-generated (summer) wave heights. Initial results suggest that the influence of shoreline stabilization efforts (primarily beach nourishment, one jetty and a few groins) has overwhelmed any wave-climate change response that may otherwise have been detectable surrounding Cape Fear, NC. Preliminary results for Fishing Point, VA indicate no discernible wave-climate related trend in shoreline change, suggesting that wave climate changes have not been of a significant magnitude to significantly influence patterns of erosion and accretion along this stretch of coastline. Coastline Evolution Model (CEM) simulations that account for beach nourishment, jetty emplacement and an increasingly high-angle wave climate produce shoreline change rate differences that are comparable to our observations. This work suggests that in areas of increasing wave energy, shoreline stabilization efforts may temporarily mask the effects of changing wave conditions on coastline response, but that changes in coastal response may be discernible via changes in shoreline stabilization efforts.