Geological Society of America

1 Assessing Coastal Vulnerability: Technical and Management Considerations

Wednesday, 20 March 2013
8:00 AM - 12:00 PM
Conference Room 6–7

POTENTIAL GEOMORPHIC CONSEQUENCES OF WAVE CLIMATE ALTERATIONS ALONG CUSPATE COASTLINES

Paper number: 1-12
Program: Theme Sessions
Time: 11:30 AM – 11:50 AM

Authors

Jennifer M. Johnson Presenting Author
University of North Carolina - Chapel Hill, Carrboro, NC
Laura J. Moore
University of North Carolina at Chapel Hill, Chapel Hill, NC
Kenneth Ells
Nicholas School of the Environment, Duke University, Durham, NC
A. Brad Murray
Nicholas School of the Environment, Duke University, Durham, NC

Abstract

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 compare historic and recent patterns of erosion and accretion for areas surrounding Cape Fear, NC to determine if a similar coastline response can be detected for locations heavily impacted by shoreline stabilization efforts.

We obtained shorelines from a suite of sources for this location 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) has overwhelmed any wave-climate change response that may otherwise have been detectable surrounding Cape Fear, NC. Coastline Evolution Modeling (CEM) simulations that include similar patterns of nourishment produce shoreline change rate differences comparable to our observations and beach nourishment trends that match our observations best when an increasingly high-angle wave climate change is included. 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 effort.