HR: 17:15h
AN: H34C-06    [Abstracts]
TI: Correlation of Shore-Oblique Bars and Nearshore Gravel Outcrops With Shoreline Change in North Carolina
AU: * Schupp, C A
EM: Courtney\_Schupp@nps.gov
AF: Virginia Institute of Marine Science, P.O. Box 1346 Route 1208 Greate Road, Gloucester Point, VA 23062 United States
AU: McNinch, J E
EM: mcninch@vims.edu
AF: Virginia Institute of Marine Science, P.O. Box 1346 Route 1208 Greate Road, Gloucester Point, VA 23062 United States
AU: List, J H
EM: jlist@usgs.gov
AF: U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, MA 02543 United States
AB: The interaction between the surf zone and the subaerial shoreface is important for data interpretation, holistic understanding of coastal zone dynamics, and the development of predictive engineering models. Previous studies have noted the existence of beach-surf zone interactions, but in general, relationships between seafloor features and coastal change are poorly quantified. This study demonstrates the physical concurrence of shore-oblique bars and gravel outcrops observed in the surf zone along the northern Outer Banks of North Carolina. It then details, both qualitatively and quantitatively, the relationships between these subaqueous features and shoreline change on a range of temporal and spatial scales. The surf zone and nearshore region of the Outer Banks are predominantly planar and sandy, but there are several discrete regions with shore-oblique bars and interspersed gravel outcrops. These bar fields are several kilometers wide alongshore and were relatively stationary over a 1.5-year survey period. Cross-covariance analysis quantifies the spatial relationships between the locations of offshore features including gravel outcrops, shore-oblique bars, and the subaerial beach response, represented by shoreline change calculated from 100-year, 28-year, and monthly datasets. Results demonstrate that areas with shore-oblique bars and gravel outcrops are strongly correlated with areas of both high short-term shoreline variability and high long-term shoreline change trends. High shoreline erosion occurs onshore of shore-oblique bar fields, but not all of the shore-oblique bars are associated with high long-term shoreline change. On a regional scale, bathymetry (as measured by the distance between the shoreline and the 9 m contour) is correlated most highly with shoreline variability at 220 m lag and with long-term change at a lag of 280 m, a very small distance considering the width of the bars (hundreds of meters) and their oblique angles to shore. Presented results will demonstrate high correlation between shoreline change on several scales and the adjacent surf-zone bathymetry and sediment distribution.
DE: 4546 Nearshore processes
DE: 3020 Littoral processes
DE: 3022 Marine sediments--processes and transport
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting