COMBINED MULTIBEAM BATHYMETRY DATA FROM RHODE ISLAND SOUND AND BLOCK ISLAND SOUND – A REGIONAL PERSPECTIVE

Detailed bathymetric maps of the sea floor in Rhode Island and Block Island Sounds are of great interest to the New York, Rhode Island, and Massachusetts research and management communities because of this area's ecological, recreational, and commercial importance. Geologically interpreted digital terrain models from individual surveys provide important benthic environmental information, yet many applications of this information require a geographically broader perspective. For example, individual surveys are of limited use for the planning and construction of cross-sound infrastructure, such as cables and pipelines, or for the testing of regional circulation models. To address this need, we integrated 14 contiguous multibeam bathymetric datasets that were produced by the National Oceanic and Atmospheric Administration during charting operations into one digital terrain model that covers much of Block Island Sound and extends eastward across Rhode Island Sound. The new dataset, which covers over 1244 square kilometers, is adjusted to mean lower low water, gridded to 4-meter resolution, and provided in UTM Zone 19, NAD 1983 projection and WGS 1984 geographic coordinates. This resolution is adequate for sea-floor geomorphic feature and sedimentary process interpretation but is small enough to be queried and manipulated with standard GIS programs. Natural features interpreted from the data include boulder lag deposits of the winnowed Pleistocene terminal and recessional end moraines, fields of transverse and barchanoid sand waves, scour depressions that reflect the strength of oscillating tidal currents, and scour by storm-induced waves. Bedform asymmetry allows interpretations of net sediment transport. Anthropogenic features interpreted from the data include shipwrecks and dredged channels. The merged data reveal a larger, more continuous perspective of bathymetric topography than previously available and provide a fundamental framework for research and resource management activities within this area of the inner continental shelf.