HR: 14:25h
AN: H33L-04    [Abstracts]
TI: Mutli-Temporal Analysis of Beach Morphology on Fire Island, NY and the Impacts of Human Alterations Within the System
AU: * Hapke, C
EM: chapke@usgs.gov
AF: U.S. Geological Survey, 339 Woodward Hall University of Rhode Island, Kingston, RI 02881, United States
AU: Lentz, E
EM: larikachica@mail.uri.edu
AF: University of Rhode Island, Department of Geosciences, Kingston, RI 02881, United States
AU: Kratzmann, M
EM: mkratzmann@mail.uri.edu
AF: University of Rhode Island, Department of Geosciences, Kingston, RI 02881, United States
AU: Bradley, M
EM: mike@edc.uri.edu
AF: University of Rhode Island, Department of Natural Resource Sciences, Kingston, RI 02881, United States
AB: Fire Island is a barrier island that lies along the south shore of Long Island, New York. Fire Island National Seashore comprises the majority of the island and a number of private communities are located within the boundary of the Seashore. The beach-front houses within the communities are generally built on or just behind the primary dune. A series of severe storms in the early 1990s resulted in widespread erosion and prompted many communities to begin a program to create protective, artificial dunes by bulldozing sand from the berm to the back beach area: a practice known as beach scraping. The National Park Service grants the permits for scraping, and there is some concern as to whether morphologic alterations to the beach and dune from scraping may be permanently impacting the natural resources in the park, both in the scraped and adjacent non-scraped and undeveloped areas. A study is currently underway to characterize the geomorphology of the beach/dune system on Fire Island and is presently focused on assessing beach and dune change at storm-event, seasonal, and decadal time scales, based on both field data and existing lidar, beach profile and shoreline data. Semi-annual topographic beach surveys are being conducted to map seasonal variations. These data, along with lidar, are being used to calculate seasonal and storm volumetric beach changes as well as assess shoreline change. The volumetric change analysis from 1998 to 2007 indicates that the beach and dune are in a dominantly erosional state. However, shoreline change analyses over both the long-term (30-year) and short-term (seasonal and storm) indicate a relatively uniform pattern of erosional and accretional cells that range from approximately 0.8 to 1.0 km in length. These correspond to alongshore undulations in beach width that are clearly visible in aerial photography. The long-term and seasonal patterns of shoreline change suggest that the cells occur as pulses of sediment that rapidly move in a longshore, westward direction. Previous shoreline change studies, conducted, at a broader spatial scale, show larger cells ranging from 8 to 10 km in length. These larger undulations appear to remain somewhat stationary over decadal timescales, and thus result in chronic erosion hotspots which lead to increased requests for permits to alter the beach. The reduction in the elevation of the beach from scraping, and the relocation of material from the berm to the foredune, where it is less likely to be mobilized during seasonal events, exacerbates the erosion, and slows the pulses of material that naturally move alongshore.
DE: 1815 Erosion
DE: 4217 Coastal processes
DE: 4558 Sediment transport (1862)
SC: Hydrology [H]
MN: 2007 Fall Meeting