SPATIAL AND TEMPORAL VARIABILITY IN BEACH TOPOGRAPHY ON A SOUTH-FACING BARRIER BEACH, OAK ISLAND, NORTH CAROLINA

Empirical Orthogonal Function (EOF) analysis is a statistical tool used by geologists to identify dominant spatial and temporal patterns of variability in data that has been repetitively measured, such as beach topography. These patterns can often be linked to physical forcing functions, such as local wind and wave conditions, to identify the dominant processes driving shoreline change. In this study, EOF analysis was used to identify patterns of variability in 12 beach profile transects surveyed along the western 14 km of Oak Island, North Carolina. Oak Island is a 23 km-long south-facing barrier beach on the western flank of the Cape Fear foreland. It is bordered by Lockwood's Folley Inlet to the west and the Cape Fear River Inlet to the east. Beach profiles were surveyed from the primary dune to approximately mean low water bimonthly from June 2004 to June 2006 using a kinematic GPS. An EOF analysis was conducted on each survey transect time series to compare patterns of variability across the study reach. Also, the local wind and wave climates were analyzed during the study period to determine whether patterns observed in these data correlate with patterns of variability identified in the EOF analysis. Preliminary results reveal both seasonal patterns of variability in beach surface elevation and long term trends that may be associated with physical processes operating at lower temporal frequencies.