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SPCMSC Research Geologists Emily Wei and Jennifer Miselis published a new paper titled, “Geologic Framework, Anthropogenic Impacts, and Hydrodynamics Contribute to Variable Sediment Availability and Shoreface Morphology at the Rockaway Peninsula, NY” in the Journal of Marine Science and Engineering.

Two scientists walk on the beach beside an eroding bluff under a boardwalk at Rockaway, NY
Scientists walk on the beach beside a boardwalk that sits on an eroding bluff at the Rockaway Peninsula, New York. A new study investigates the geologic framework and how human modifications to the coast have influenced sediment availability on this margin.

Recent work in the field of coastal geomorphology has highlighted the need for more detailed information about the geology and morphology of the shoreface, which remain critical knowledge gaps. The shoreface is a transition zone and temporary sediment reservoir between the shoreline and the shelf, and can store sediment eroded from the beach and supply sediment to beaches through onshore transport. Understanding how geology, human modifications to the coastline, and waves will affect how shorefaces respond to storms and sea-level is especially important at the Rockaway Peninsula, NY, which withstood extensive damage to the coast following Hurricane Sandy (2012). Using multibeam bathymetry, chirp seismic reflection, and surficial sediment grain size, we quantified the volume of available sediment and improved understanding of the shoreface geologic framework. Chirp seismic data revealed significant variability in sub-seafloor geology and shoreface volume over a relatively short span of the coastline (< 20 km). We also used chirp data to delineate a geologically defined shoreface, and, using a novel approach, found that the geologically defined shoreface may be reworked on timescales of years to decades. This suggests that traditional methods that use the wave-based shoreface extent to estimate shoreline response to sea-level rise may overestimate the magnitude of shoreward fluxes. Finally, we found that human modifications to the beach, such as groins, jetties, and beach nourishment, may steepen the upper shoreface, which may promote further changes in shoreface morphology and sediment fluxes. Our results demonstrate that the combination of waves, humans, and geology formed over years to millennia causes significant variability in shoreface volume and as a result, the Rockaway Peninsula may respond to climate-driven changes in storminess and sea level in nonuniform ways. 

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