The USGS, in cooperation with NOAA and the CT DEP, is producing detailed maps of the sea floor in Long Island Sound. The current phase of this cooperative research program is directed toward studies of sea-floor topography and its effects on the distributions of sedimentary environments and benthic communities. Because anthropogenic wastes, toxic chemicals, and changes in land-use patterns resulting from residential, commercial, and recreational development have stressed the environment of the Sound, and caused degradation and potential loss of benthic habitats, detailed maps and interpretations of the sea floor are needed to evaluate the extent of adverse impacts and to manage resources wisely in the future.

The bathymetric data released in this report were derived from NOAA bathymetric surveys conducted off New London and Niantic, Connecticut. We have merged the data from multibeam surveys H11441 and H11442, conducted in deeper waters, with those from hydrographic LIDAR surveys H11224 and H11225, conducted in adjacent nearshore shallower waters. Together these merged data reveal a larger, more continuous perspective of sea-floor topography than previously available and provide a fundamental framework for research and resource management activities along this part of the Connecticut coastline.

Surveyed depths within the study area range from sea level at mean lower low water to more than 65 m. The shallowest areas occur along shorelines and on isolated bathymetric highs, such as Bartlett Reef and Twotree Island. Exposed bedrock outcrops, boulder lag deposits, sand-wave fields, and scour depressions reflect the strength of the oscillating tidal currents. Anthropogenic artifacts visible in the bathymetric data include a dredged channel, shipwrecks, dredge spoils, mooring anchors, prop-scour depressions, buried cables, and bridge footings.