Abstract

Topographic organization of the shorezone was documented by two beach profile data sets covering a 71-km reach of the Outer Banks, North Carolina. The earliest profiles (1937) were surveyed during the period of initial man-made dune stabilization by the Civilian Conservation Corps. A 1976 set comprises profiles that have been adjusting for 40 years to the presence of the dunes. Principal components analysis was used to partition the topographic variance of the beach profiles into a few major definable and uncorrelated modes of variation. The first three principal components for each profile data set explain approximately 90% of the variance, suggesting a high degree of topographic organization of the shorezone. The along-the-coast weightings for each principal component were analyzed with spectral analysis so that significant alongshore periodicities could be identified. Cross-spectral analysis was then performed on the weightings for each data set to determine the alongshore covariance. The dune stabilization has caused narrowing of the active beach width and steepening of the beach profile over a period of 40 years. However, the long-term topographic organization, as defined by the eigenvectors, has remained essentially intact.

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