5-6 Assessment of Dune Overtopping Vulnerability and Overwash Sediment Characterization along Staten Island Beaches

Session: Nearshore and Estuarine Research: Dynamics and Future Resiliency in the Coastal Zone (Posters)

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Abstract:

Beach dunes are natural protective barriers between the ocean and back barrier zones. Coastal storms are capable of driving water and waves high enough on the beach that it causes overtopping of the dunes. Severe overtopping can result in inundation of the backshore, transporting sediment as overwash deposits. The vulnerability of 7 transects along Staten Island’s eastern shore is determined using field measured beach angles and historical wave and water-level records. The historical data is used together with Stockdon’s R₂% runup formula to determine overtopping events over a time period of four years, accounting for dune crest elevation variability. In addition, transects are set against Superstorm Sandy condition, as well as Nor’easter conditions, with different crest elevations to determine vulnerability to similar storms. Sediment analysis from coring wetlands behind the dunes will characterize past overwash deposits. Visualization of this data shows up to 25 events of overtopping in the past four years for South Beach and New Dorp Beach, while Midland Beach had up to 5. The number of overtopping events increases yearly. Beach profile comparisons show significant change in some areas, which may indicate beach erosion, resulting in the increasing sensitivity to overtopping. This vulnerability assessment will help inform strategies for preventing inundation as a result of future intense storms.

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