Introduction

In 1996 and 1997, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, conducted a program to produce geologic framework maps of the nearshore areas south of Long Island, New York (Schwab and others, 1997; Foster and others, 1999; Schwab, Thieler, Allen, and others, 2000). Mapping methods included high-resolution sidescan-sonar and seismic-reflection techniques. The goal of this investigation was to determine regional-scale availability of sand as a resource for future beach nourishment programs and to investigate the role that inner continental shelf morphology and geologic framework have in the evolution of the coastal region of southern Long Island.

In 2011, a high-resolution marine geophysical survey of the lower shoreface and inner continental shelf was conducted offshore of Fire Island, New York (Schwab, Denny, and Baldwin, 2014). This report presents maps of the change in modern sediment thickness and distribution detected between the 1996–97 and 2011 mapping investigations. The results suggest that the nearshore/shoreface sedimentary deposit has gained sediment at the expense of continued erosion of the marine transgressive surface. This report adds to a scientific foundation used to manage coastal systems and assess environmental changes caused by natural processes and human activities.