HUMAN IMPACTS ON NEW YORK CITY BARRIER DEVELOPMENT

Barrier systems are one of the most important forms of storm defense for New York City. The entrance to New York Harbor is formed by two sandy peninsulas (Rockaway to the north and Sandy Hook to the south) while a series of smaller barrier systems within the harbor proper provide a secondary means of flood mitigation. An accurate understanding for the evolution of these barrier systems over the later-Anthropocene is critical for assessing the effectiveness of future flood control strategies. Man-made impacts to the Rockaway and Sandy Hook spits are well documented and will be reviewed in brief. We will follow this discussion with a more detailed description of backbarrier sediments recently collected along the inner coastline of New York Harbor. A cotemporaneous transition from an estuarine to a lagoonal environment is observed in all three of these backbarrier ponds dating to the early-to-mid 1700s. Overwash deposition begins above this transition and marks the establishment of sandy barriers in their current form. The concurrent timing of barrier formation dates to rapid land clearance and the decimation of oyster beds in the harbor. Both of these changes likely enhanced shoreline erosion and increased littoral transport, which in turn led to the formation of many of the barrier systems internal to New York Harbor. Results presented highlight how past human activities have been of leading importance in governing the development of New York City’s barrier beaches, which together now serve as the most important line of flood defense to the largest coastal mega-city in the Western Hemisphere.