Date of Award

Summer 1990

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

John C. Ludwick

Committee Member

George F. Oertel

Committee Member

Dennis A. Darby

Committee Member

Carvel Blair

Call Number for Print

Special Collections LD4331.O35R39

Abstract

The influence of shoreline structures on longshore sediment transport and the evolution of a stable beach planform was investigated at Willoughby Spit, Virginia following the placement of 410,590 cubic meters of beach fill within a groin system. Shoreline changes and wave conditions in a single groin compartment, and the growth rate of a downdrift terminal spit were monitored during 1985 and 1986. Short term fluctuations in the shoreline position within the groin compartment suggested an episodic westerly movement of sediment through the groin system. Primary sediment moving events were associated with northerly winds which produced waves up to 50 cm in height. Breaker angles, opening to the west, ranged from 5-30 degrees. Under these conditions wave heights within the compartment increased in a shore wise direction to the west. The growth rate of the terminal spit was linear, with the spit achieving a total volume of 38,500 cubic meters by the end of the study period, or nine per cent of the total volume of fill material for the project.

Sediment losses from the groin system resulting from longshore transport were attributed to groin overtopping and rip currents created as shore parallel currents encounter the groin wall and are deflected seaward. The groins were found to affect longshore sediment transport and shoreline response by 1) segmenting the shoreline; 2) altering wave approach; 3) attenuating wave height and; 4) deflecting the longshore current seaward. Evolution of the stable shoreline configuration is dependent on sediment input to the compartment and the special wave height distribution.

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DOI

10.25776/93j6-d305

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