Long-Term Change - Coastal System Change at Fire Island, New York
Long-term coastal change can occur over historical (10s to 100s years) and geological time scales (100s-1000s years). At Fire Island, the historical record of the position of the island goes back to the 1800s. Changes since then are quantified using historical maps, aerial photos, and modern coastal mapping techniques.
By studying long term coastal changes and behavior at Fire Island, USGS researchers are able to measure and evaluate how the island has evolved through time, and therefore better understand where future change may be most likely. Long-term coastal change occurs over historical (10s to 100s of years) and geological time scales (100s-1000s of years). At Fire Island, the historical record of the position of the island goes back to the 1800s, which has been captured in maps and aerial photos collected since that time.
Analyses of 80-years of shoreline change and 40-years of morphologic change demonstrate distinct variations in island behavior over time periods ranging from decades to centuries. Changes have been linked with human activity, as well as documented variations in island morphology, and offshore geologic features which influences the wave energy reaching the coast.
Morphologic Change
An assessment of morphologic change for the beaches and dunes at Fire Island over a 40 year period (from 1969 to 2009) shows changes are linked with human activity, as well as documented variations in island morphology, and offshore bathymetry which influences the wave energy reaching the coast. The western reach of the island has an ample sediment supply, demonstrated through rapid growth of Democrat Point over the last several centuries. The western and central portions of the island are linked with offshore geologic features, and home to a number of communities where replenishment projects have occurred over the years.
Shoreline Dynamics
A study of alongshore variation of shoreline change shows distinct differences in the movement and position of this dynamic feature. The shoreline assessment was conducted using a database of over 35 shorelines spanning nearly 80 years (1933-2012) and is regularly updated as new data are available.
The shoreline change pattern appears to be largely controlled by the regional geology. The 80-year shoreline change record demonstrates three distinct zones of behavior. To the east, the overall pattern is long-term, persistent erosion and corresponds to the portion of the island that has been shown to be moving landward over much longer time scales (centuries and longer).
Shoreline behavior along the western portion of the island is more variable than other portions of the island, and the average net change is near zero (although there are zones of erosion and accretion). The patterns of change are pervasive and repeating and have a length scaling similar to the field of sand ridges mapped on the adjacent seabed.
The central portion of the barrier is exhibiting seaward progradation over the time-scale of this analysis. This area of gain corresponds to the offshore location of a lobe of glaciofluvial sediment that is linked to a bathymetric high on the seabed. The island is also on average higher in elevation in this area making it less susceptible to erosion.
Below are other science projects associated with this project.
Coastal System Change at Fire Island, New York
Back-barrier and Estuarine - Coastal System Change at Fire Island, New York
Oceanside Beaches and Dunes - Coastal System Change at Fire Island, New York
Open Ocean/Marine - Coastal System Change at Fire Island, New York
Nearshore - Coastal System Change at Fire Island, New York
Long-term coastal change can occur over historical (10s to 100s years) and geological time scales (100s-1000s years). At Fire Island, the historical record of the position of the island goes back to the 1800s. Changes since then are quantified using historical maps, aerial photos, and modern coastal mapping techniques.
By studying long term coastal changes and behavior at Fire Island, USGS researchers are able to measure and evaluate how the island has evolved through time, and therefore better understand where future change may be most likely. Long-term coastal change occurs over historical (10s to 100s of years) and geological time scales (100s-1000s of years). At Fire Island, the historical record of the position of the island goes back to the 1800s, which has been captured in maps and aerial photos collected since that time.
Analyses of 80-years of shoreline change and 40-years of morphologic change demonstrate distinct variations in island behavior over time periods ranging from decades to centuries. Changes have been linked with human activity, as well as documented variations in island morphology, and offshore geologic features which influences the wave energy reaching the coast.
Morphologic Change
An assessment of morphologic change for the beaches and dunes at Fire Island over a 40 year period (from 1969 to 2009) shows changes are linked with human activity, as well as documented variations in island morphology, and offshore bathymetry which influences the wave energy reaching the coast. The western reach of the island has an ample sediment supply, demonstrated through rapid growth of Democrat Point over the last several centuries. The western and central portions of the island are linked with offshore geologic features, and home to a number of communities where replenishment projects have occurred over the years.
Shoreline Dynamics
A study of alongshore variation of shoreline change shows distinct differences in the movement and position of this dynamic feature. The shoreline assessment was conducted using a database of over 35 shorelines spanning nearly 80 years (1933-2012) and is regularly updated as new data are available.
The shoreline change pattern appears to be largely controlled by the regional geology. The 80-year shoreline change record demonstrates three distinct zones of behavior. To the east, the overall pattern is long-term, persistent erosion and corresponds to the portion of the island that has been shown to be moving landward over much longer time scales (centuries and longer).
Shoreline behavior along the western portion of the island is more variable than other portions of the island, and the average net change is near zero (although there are zones of erosion and accretion). The patterns of change are pervasive and repeating and have a length scaling similar to the field of sand ridges mapped on the adjacent seabed.
The central portion of the barrier is exhibiting seaward progradation over the time-scale of this analysis. This area of gain corresponds to the offshore location of a lobe of glaciofluvial sediment that is linked to a bathymetric high on the seabed. The island is also on average higher in elevation in this area making it less susceptible to erosion.
Below are other science projects associated with this project.