Long Island Sound is one of the largest estuaries along the Atlantic coast of the United States. It is a glacially produced, semi-enclosed, northeast-southwest-trending embayment, which is 150 km long and 30 km across at its widest point. Its mean water depth is approximately 24 m. The eastern end of the Sound opens to the Atlantic Ocean through several large passages between islands, whereas the western end is connected to New York Harbor through a narrow tidal strait. Long Island Sound abuts the New York-Connecticut metropolitan area and contains more than 8 million people within its watershed. A study of the modern sedimentary environments on the sea floor within the Long Island Sound estuarine system was undertaken as part of a larger research program by the U.S. Geological Survey (Coastal and Marine Geology Program) conducted in cooperation with the State of Connecticut Department of Environmental Protection and the U.S. Environmental Protection Agency. Knowledge of the bottom sedimentary environments was needed to discern the long-term fate of wastes and contaminants that have been, or potentially will be, introduced into the system and to help understand the distribution of benthic biologic habitats.

The original interpretation was hand-drawn on mylar based on sidescan-sonar data, seismic-reflection profiles, and sediment sample data collected in the study area. The extent of this orginal work only extended shoreward to the 10m contour interval. This interpretation was then digitized on a digitizing table. This line information was then transferred to Arc/Info where significant cleaning of the data was done. These arcs were then converted to polygons and the attribute information attached. Subsequently, data from the 10 m contour shoreward was incorporated into the original mylar interpretive map. These changes were then digitized and incorporated into the existing Arc/Info coverage. Again, significant cleaning of the arcs as well as assigning the attribute information was done in Arc/Info. The original projection of this work was UTM zone 18, NAD27. For this publication, these data were reprojected into UTM zone 18 NAD 83.