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Open-File Report 2014–1012

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### Combined Multibeam Bathymetry Data from Rhode Island Sound and Block Island Sound – A Regional Perspective 

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## Summary 

| Title PageList of FiguresConversion FactorsAbstractIntroductionMethodsBathymetryGIS Data Catalog**Summary**AcknowledgmentsReferencesContactsIndex | The  U.S. Geological Survey (USGS), in cooperation with the National Oceanic and  Atmospheric Administration (NOAA), has produced detailed maps of the sea floor  in Rhode Island and Block Island Sounds. As part of this program, digital  terrain models (DTMs) from bathymetry collected as part of NOAA's hydrographic  charting activities are converted into Esri raster grids and imagery (primarily  of 2-meter resolution), verified with bottom sampling and photography, and used  to produce interpretations of seabed geology and hydrodynamic processes.  Although each of the completed surveys individually provides important benthic  environmental information, many applications require a geographically broader  perspective. For example, the usefulness of individual surveys is limited for  planning and construction of cross-sound infrastructure, such as cables between  Block Island and the mainland, or for testing of regional circulation models.  To address this need, we integrated 14 multibeam bathymetric DTMs into one contiguous  dataset that covers much of Block Island Sound and extends eastward across  Rhode Island Sound. The new dataset is adjusted to mean lower low water, is  provided in Universal Tranverse Mercator (UTM) Zone 19, North American Datum of  1983 (NAD 83), and geographic World Geodetic System 1984 (WGS 84) projections,  and is gridded to 4-meter resolution. This resolution is adequate for sea-floor-feature  and process interpretation but small enough to be queried and manipulated with  standard geographic information system (GIS)  programs and to allow for future growth.

Surveyed  water depths within the study area range from near sea level to more than 103  meters. Specific morphological features that indicate sea-floor geology,  sedimentary processes, benthic environmental energy, and anthropogenic effects  are readily identified in the DTM. Conspicuous natural features include boulder  lag deposits of winnowed Pleistocene glacial drift, fields of sand waves and  megaripples, and scour depressions that reflect the strength of the oscillating  tidal and storm-wave-induced currents. Bedform asymmetry allows interpretations  of net sediment-transport direction. Anthropogenic artifacts visible in the  bathymetric data include dredged channels and shipwrecks. Together the merged  data reveal a larger, more continuous perspective of bathymetric topography  than previously available, providing a fundamental framework for research and  resource-management activities off the Rhode Island coast. |
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U.S. Department of the Interior |            U.S. Geological Survey                                                URL: http://pubs.usgs.gov/of/2014/1012/html/summary.html            Page Contact Information: GS Pubs Web Contact                        Page Last Modified: Friday, February 21, 2014, 12:07:12 PM