Coastal Change at Fire Island, a geonarrative

Science Center Objects

Approximately 60 miles from the skyscrapers and fast-pace of New York City, Fire Island stretches 31 miles along the south shore of Long Island. The sandy beaches and pristine wilderness areas of Fire Island National Seashore are dotted with secluded residential communities. The island is fronted by the Atlantic Ocean, so in addition to its natural and recreational value, Fire Island is also Long Island's first line of defense against seasonal and tropical storms. For more than two decades the U.S. Geological Survey has been researching Fire Island's offshore, nearshore, and barrier island systems to better understand drivers of coastal change and evolution.

This geonarrative delves into how barrier islands change and evolve, demonstrates how seasons, storms and humans change beaches, and explores the role models play in predicting what the beach might look like 'next summer'.

 

Discover the technology and tools used to monitor the state of the beaches. Dynamic coasts such as Fire Island change in response to wind, waves, tides, sediment supply, human-induced changes, and sea-level rise. They can change rapidly in response to storms or more gradually in fair weather in response to seasonal and annual cycles. 

Explore how the western shoreline has changed since 1830. Long-term coastal change can occur over historical (tens of years) and geological time scales (hundreds to thousands of years). At Fire Island, the historical record of the position of the island goes back to the 1800s, and we can quantify the island's changes by looking at historical maps and aerial photos collected since that time. The western part of the island, a prograding spit, has grown more westward over historical time scales. Western Fire Island has a lot of sand, and the spit has extended as sediment transport has moved westerly across the island, causing Fire Island Inlet to migrate. Dynamic features such as the spit can be challenging for navigation; as a result, the inlet was “stabilized” through the emplacement of a groin in 1941 and regular dredging since the 1950s.

Observe examples of storm induced, seasonal, and interannual changes. Waves, winds, tides, and weather fluctuate with the seasons. Hurricanes occur in the summer and autumn, whereas Nor'easters occur in winter and spring in the Northeast, meaning coasts in this region may experience major storms nearly year-round.  

Learn how models allow us to understand the drivers and processes involved in coastal change. Coastal-change computer models allow us to understand the drivers and processes involved in coastal change. For example, models help us better understand why erosion from a particular storm may occur in some places and not others. Observations provide an important mechanism to test and evaluate our models.

East end of Fire Island depicted with airborne imagery and lidar

East end of Fire Island, showing white sandy beaches and marshes, depicted with airborne imagery, and lidar-derived bathymetric features in the estuary behind the island, in the offshore region, and in the channel connecting the estuary to the ocean. 

(Public domain.)