ASSESSING THE STABILITY OF STATEN ISLAND'S EASTERN SHORE: A SEDIMENT ANALYSIS

For years, the eastern beaches on Staten Island, New York have been undergoing coastal engineering and replenishment, especially after the devastation and inundation caused by Hurricane Sandy. Understanding the processes operating on these beaches is essential to assessing future risks and planning coastal defenses. In this study, sediment samples were collected at low tide from transects on the eastern beaches of Staten Island over the course of a year. Each transect included samples from 1m water depth (offshore), the low tide mark, and the beach face. These samples were analyzed for grain size distribution to confirm that the beaches have the characteristics of a reflective beach. The results show that there are minimal changes to grain size distribution over time. Offshore samples are the most variable, with mean grain size from fine sand to very coarse sand. The low tide mark is characterized by a ridge of sediment that is mostly sandy gravel and gravelly sand. Beach face sediments are generally medium to coarse sands, while medium sands are found higher on the beach profile. These characteristics indicate reflective beaches. Therefore, there should be minimal changes expected to the coastline year by year. One part of the beach that is subject to the most erosion is protected by an artificial dune, which erodes and supplies sand to the beach during storm events. In this area, we observed that the beach sediment is more fine-grained than elsewhere, suggesting that the artificial dune is not composed of sand that is typical of the natural beach. However, as a reflective coastline, it remains extremely vulnerable to storms, which would have the potential to significantly alter the beaches over a short amount of time. Plans for the eastern coast of Staten Island include the construction of a buried seawall, covered in sand, to protect low-lying residential areas from the effects of future storms. Sea walls potentially increase beach erosion, although this design should “feed” the beach with sand when it is eroded. Future sample collection and analysis after the completion of the seawall will show if there are any significant changes to the Staten Island beaches as a result of this construction.