Open-File Report 2015-1033
Coastal erosion is pervasive along much of the world's shoreline. The ability to understand and predict coastal change is important with regard to mitigating hazards. Storms are one of the primary forces driving coastal change. The duration, magnitude, and frequency of storms determine the long-term sediment flux of the region (Warner and others, 2012). These discrete storm events can create large waves, storm surges, flooding, coastal erosion, and strong currents that affect life, property, and navigation. Understanding these processes is critical to the assessment of coastal change and the cumulative effect of storms over varying timescales. Understanding coastal change enables planners and coastal managers to provide increased awareness and advanced preparation to help minimize loss of life and property and to manage coastal resources.
The U.S. Geological Survey Coastal Change Processes Project is researching coastal change hazards through geologic framework studies, numerical models, and physical oceanographic observations. These integrated efforts address issues related to coastal change caused by storm effects; sediment budgets; and sediment-transport linkage among the beach, the shoreface, and the inner shelf. Additional information about the project is available at the USGS Woods Hole Coastal and Marine Science Center Coastal Changes Processes Project Web page ( http://woodshole.er.usgs.gov/project-pages/coastal_change/).
The Coastal Change Processes Project has conducted field experiments at several locations along the east coast of the United States. This particular field program was focused on the region along Fire Island, N.Y., a barrier island system along the southern shore of Long Island, N.Y. This region was greatly impacted by Hurricane Sandy in October 2012.
Fire Island is bounded by Fire Island Inlet to the west and Moriches Inlet to the east. The barrier island itself provides a natural defense from the impacts of waves and large storm events for the densely developed mainland. Fire Island is 0.5–1-km wide and contains many different (and sometimes conflicting) land uses such as the Fire Island National Seashore, State parks, a Federal wilderness area, and a number of coastal communities. Sections of Fire Island have high rates of coastal erosion, whereas other areas are relatively stable (Hapke and others, 2010; Schwab and others, 2013). A principal strategy to mitigate coastal erosion is construction of sand berms, dunes, and regular beach nourishments with sediment dredged from the adjacent inner continental shelf. Remnant borrow locations are visible in the bathymetric data. However, it is not well understood how changes to these adjacent inner continental shelf locations can potentially affect the nearshore coastal region. This study focused on addressing how changes in sea-floor topography can create variations in waves along the coast, possibly resulting in regions of erosion and accretion. The study also focused on how the cross-shore variations in waves and currents can drive cross-shore sediment fluxes.