Coastal foredune displacement and recovery, Barrett Beach-Talisman, Fire Island, New York, USA

Abstract

Coastal foredune mobility has been tracked at Fire Island National Seashore since 1976 with annual field surveys and analysis of frequent aerial photography. Sequential mapping of the foredune crestline depicts nearly islandwide displacement during major storm events, such as in 1992, and localized displacement during alongshore passage of inshore circulation cells during other years. An instance of localized landward erosion and curvilinear displacement along approximately 400 m of foredune occurred in 1994, followed by recovery over the next nine years. Data from annual surveys and partially supported by four LIDAR flights establish that volume recovery rates in the foredune ranged from about 1.0 m3/m/yr to nearly 12.0 m3/m/yr. Analysis of the foredune morphology and location shows nearly complete recovery of foredune shape and dimension during this interval and it also demonstrates that there has been inland displacement of the foredune crestline of up to 40 m. Total volume recovery within the localized foredune erosion site was greatest, between 34 m3/m to 47 m3/m, in areas of greatest displacement and eventually contributed to creation of a foredune of similar dimension along the entire eroded zone. This process of erosion and recovery describes a mechanism for foredune dimension retention during episodic erosion and displacement and may be a model for foredune persistence accompanying barrier island migration.