SEDIMENTARY EVIDENCE OF RECENT HURRICANE STRIKES FROM WESTERN LONG ISLAND, NEW YORK

Landfall of intense hurricanes is difficult to predict given the significant temporal and spatial variability of intense-hurricane occurrence. Records of past hurricane activity provide probabilistic information that can be used to estimate the likelihood of a future hurricane strike at any one location. Historical records of North American hurricanes date back several hundred years, and more detailed records maintained by the National Oceanic and Atmospheric Administration date back to the mid-19th century. The relative rarity of intense hurricanes and the short observational record result in significant uncertainties associated with estimates of intense-hurricane landfall probabilities derived from the historical record. Sedimentary records of past hurricane activity can extend our knowledge of hurricane occurrence into the prehistoric period.

Since European settlement three hurricanes occurring in 1788, 1821, and 1893 have made landfall in what is now New York City, New York. The 1821 hurricane appears to have been the most intense of these storms at landfall, with nearly 4 meters of storm surge causing extreme damage in low-lying areas. Storm surges of this magnitude can overtop barrier beaches depositing sand across the surface of backbarrier marshes. These deposits are often preserved in the stratigraphic record following the subsequent accumulation of marsh peat over storm-induced deposits. Mapping and dating these storm-induced deposits provides a means of reconstructing the history of past intense storms at any particular location.

Analysis of a series of vibracores from the backbarrier marsh at Hick’s Beach, New York revealed at least three continuous sand layers preserved within the high-organic marsh sediments to a depth of 2 meters. We determined the age of these of these sand layers with radiocarbon methods, pollen analysis and evidence of lead pollution preserved in the marsh sediments. The timing of deposition of several overwash fans is consistent with known historic hurricane strikes on this coast. In addition a prehistoric overwash fan recovered at the site is of similar character and extent as the historic overwash fans and likely represents a prehistoric hurricane strike.