Coastal erosion is often related to high wave energies associated with storms, but it usually results from disparities in the coastal sediment budget introduced by longshore transport gradients. Erosion, therefore, affects low energy coastal environments as well as high energy coastal environments. The rate of longshore sediment transport is an important factor in determining erosion along a coast, and the accurate prediction of this rate is central to an understanding of coastline changes and the effects of shore protection structures. Understanding and prediction of longshore transport distribution across the surf zone requires reliable and complete field and laboratory data. This study will attempt to overcome many of the difficulties involved in mounting a comprehensive field experiment of longshore sediment transport by more accurately monitoring the variables which control sediment movement. The study will evaluate longshore sediment transport theory with data from an estuarine beach at Fire Island National Seashore. Its purpose is to gather and analyze data as a basis for managing estuarine beaches in the Seashore, and it will identify the processes that characterize wave energy and that cause erosion and changes in the beach profile. The basic equations which describe longshore sediment transport are usually tested with data from beaches and from wave tank experiments in laboratory settings. While theoretically sound, the equations are usually tested with poor quality data from beach studies. The accurate measurement of sand movement in the surf zone of a beach is critical to any study of sediment transport. The small dimensions and relatively low wave energies of estuarine beaches facilitate field sampling and enhance the accuracy of measurements. This project is designed to used specially colored sand as a tracer in order to monitor movement of sediment along a section of shoreline. This controlled experiment should generate the necessary data to accurately test the equations for longshore sediment transport. The results of this study should strengthen our understanding of sediment movement along shorelines which will lead to better knowledge of shoreline erosion rates, their possible causes, and to more effective strategies for preventing erosion along coastal areas.
