INTEGRATED MULTIBEAM AND LIDAR BATHYMETRY DATA FROM NORTHEASTERN LONG ISLAND SOUND

Nearshore areas within Long Island Sound are of great interest to the research and resource management communities of Connecticut and New York because of their ecological, recreational, and commercial importance. Although advances in multibeam echosounder technology permit the construction of high-resolution representations of sea-floor topography in deeper waters, limitations inherent in collecting fixed-angle multibeam data make using this technology in shallower waters (less than 10 meters deep) difficult and expensive. These limitations have often resulted in data gaps between areas for which multibeam bathymetric datasets are available and the adjacent shoreline. To address this problem, we integrated complete-coverage multibeam bathymetric data acquired off New London and Niantic, Connecticut, with hydrographic Light Detection and Ranging (LIDAR) data acquired along the nearshore. The resultant datasets are provided as 4-m resolution bathymetric grids in UTM Zone 18 NAD83 and geographic WGS84 projections and are adjusted to mean lower low water. Together these merged data reveal a larger, more continuous perspective of sea-floor topography with a much smaller gap between the digital bathymetric data and the shoreline than previously available.

Surveyed depths within the study area range from sea level at mean lower low water to more than 65 m. Exposed bedrock outcrops, boulder lag deposits of the Fishers Island and Clumps moraines, sand-wave fields, and scour depressions reflect the strength of the oscillating tidal currents. Bedform asymmetry allows interpretations of net sediment transport. Anthropogenic artifacts visible in the bathymetric data include a dredged channel, shipwrecks, dredge spoils, mooring anchors, prop-scour depressions, buried cables, and bridge footings. To facilitate access, compatibility, and utility, these datasets are provided online in ESRI raster-grid and GeoTIFF formats at: http://pubs.usgs.gov/of/2009/1231/