Abstract

MIGRATION AN MORPHOLOGIC EVOLUTION OF AN EBB-TIDAL DELTA SHOAL, CHINCOTEAGUE INLET, VIRGINIA

BARTLET, K. E., Department of Physical Sciences, Kutztown University, Kutztown, PA 19530; VENN, C., Department of Geosciences, Indiana University of Pennsylvania, Indiana, PA 15705; ZIMMERMAN, R., Department of Geography and Environmental Engineering, Johns Hopkins University, Baltimore, MD 21218; and SIMPSON, E. L., Department of Physical Sciences, Kutztown University, Kutztown, PA 19530.

Ebb-tidal delta shoals form as a result of the dynamic interaction of tide-, wave-, and storm- generated currents. A limited number of studies have tracked the long-term migration of an ebb-tidal delta shoal and the morphologic changes that result from the passage of a hurricane or a northeaster. We examined an ebb-tidal delta shoal in Chincoteague Inlet, Virginia by two methods. Aerial photographs from 1974 to 1991 were used to track shoal position and shoreline changes. Plane table mapping of the shoal from 1990 through 1992 allowed assessment of morphologic changes before and after the passage of storms.

Aerial photographs indicated that the shoal migrated southward from 1974 to approximately 1981; superimposed on the southward migration is a counterclockwise rotation of the shoal. From 1981 through 1991 the shoal moved first towards Wallops Island, VA, to the west, then traveled northward; superimposed on the northward migration is a clockwise rotation of the shoal. Overall the shoal is inscribing a large clockwise pattern possibly the result of wave and longshore drift interaction. Alternatively, the shift of the shoal towards Wallops Island during the overall clockwise movement may be in part the result of sediment transport landwards during storms. The smaller apparent rotations during southward and northward migration may be the result of a stronger flood tidal current in the main channel during southward migration and in the smaller southern flood tidal channel during northward migration.

Pre- and post-storm aerial photography and plane table mapping permitted the identification of the dominate processes affecting shoal morphology. Fair-weather processes, and mud sedimentation associated with a living assemblage of Diopatra cuprea. During storms, eolian dunes were planed off and sand was transported landward burying the Diopatra cuprea patch resulting in washover fan development. Significant shoreline straightening perpendicular to the wave approach was associated with storm events.

Kutztown University of Pennsylvania

A member of the State System of Higher Education

D.J. Moore
Oct. 2002
Last modified Sept. 2004
moore@kutztown.edu