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Figure 1. Index map of Long Island Sound study area, U.S. Geological Survey/ Connecticut Department of Environmental Protection surveys, and National Oceanic and Atmospheric Administration hydrographic surveys.

The U.S. Geological Survey (USGS), in cooperation with the National Oceanic and Atmospheric Administration (NOAA) and the Connecticut Department of Environmental Protection (CT DEP), is producing detailed maps of the sea floor along the northeastern coast of the United States (fig.1). Sidescan-sonar and multibeam-bathymetric data from NOAA hydrographic surveys along with sediment samples and bottom photography from USGS cruises are used to outline sedimentary environments and sea-floor features and help improve our understanding of sea-floor processes that control the distribution and movement of sediment.

This report covers a 12-km² area of Long Island Sound, north of Orient Point, NY, and contains 6.1 km² of sidescan-sonar imagery (collected in the shallower, nearshore part of the study area) and 11.6 km² of multibeam-bathymetric imagery collected during September and October 2008 as part of NOAA hydrographic survey H11446 (fig. 1). The acoustic data were verified with sediment samples and bottom photography from 26 stations occupied during April 2010 as part of USGS cruise 2010-010. This report contains data that can be displayed in a geographic information system (GIS), including sidescan-sonar imagery, multibeam bathymetric grids and imagery, sediment-sample and still-photograph locations and sedimentological statistics, and an interpretative data layer. This information is important for benthic-habitat studies and serves as a framework for future studies, including sea-floor monitoring and management activities.