Side-Scan-Sonar Points for Hudson River, NY

Side Scan Point Files. These points correspond to individual pings which produced hte side-scan-sonar backscatter imagery. Sonar data were collected November 6 to December 15, 2009, in the estuary north from Saugerties to Troy. Data Collection and Processing: The interferometric system used to measure acoustic reflectivity, provided a quantitative measure of reflectivity for every square meter of the survey area. Fugro's system measured and recorded acoustic reflectivity that has a high dynamic range such that the full range of reflectivity's encountered in the estuary environment can be recorded while maintaining a constant gain setting on the system receiver. Reflectivity data from the GeoSwath was used to produce a normalized as well as a classified image of the bottom. Additionally, Fugro provided slope, aspect and hillshade models as additional acoustic parameters. Backscatter data processing was completed with CARIS 7.0. Raw XTF files were created by converting Hypack format (*.HSX) into Triton format (*.XTF). Points were exported from the raw XTF files at an interval of 400 pings (approximately 100 meters).

Original contact information:

Contact Name: John Ladd

Contact Org: Hudson River National Estuarine Research Reserve, NYS DEC

Phone: 845-889-4745

Email: jxLadd@gw.dec.state.ny.us

Our work was consistent with the Statement of Work prepared by the New York State Department of Environmental Conservation (NYSDEC) to develop detailed bathymetric maps, acoustic reflectivity and acoustic character maps of the shallow portions of the Hudson River Estuary from the Verrazano Narrows north to the federal dam in Troy. In addition NYSDEC requested the collection of grab samples and 100 sediment cores at least one meter in length distributed throughout the same shallow portions of the Estuary. This project was being conducted as part of the Hudson River Estuary Action Plan promulgated by NYSDEC and approved by the Governor in 1996 which committed the State to, among other things, -Conduct a submerged habitat inventory to define areas most in need of protection for Hudson River fish, blue crab, and food chain species. -To conserve, protect, and, where possible, enhance critical river and shoreline habitats to assure that the life cycles of key species are supported for human enjoyment and to sustain a healthy ecosystem. -To conserve for future generations the rich diversity of plants, animals and habitats that are key to the vitality, natural beauty and environmental quality of the Hudson River Valley. Previous work in the Estuary was limited, in that detailed bathymetry was not acquired in areas of the estuary shallower than about 4 meters due to financial constraints. About a third of the estuary was not surveyed this third is the area that is home to important submerged aquatic vegetation (SAV) beds which sustain much of the biologic community in the estuary. Utilizing advanced technology and the experience of the previous benthic mapping projects, this project provided NYSDEC maps of the shallow areas that were not addressed with the previous studies. Pilot studies (Maher, 2006; Strayer et al., 2006; Yeung and McConnaughey 2008) have indicated that variations in remote sensing acoustic data are strongly correlated to variations in benthic macro invertebrate communities. This primary goal of this project, guided by NYSDEC, was to acquire acoustic data in the shallow water areas of the estuary that would facilitate classification of the substrate into biologically significant units.

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Geographic limits of the project survey covered some or all shallow areas of the estuary from the Verrazano Narrow Bridge north to the federal dam at Troy. The landward limit of surveys along the eastern shore of the estuary was the low tide line or the railroad tracks that extend up the east shore of the estuary whichever was most westward on a given line of latitude including Schodack Creek north to Little Schodack Island. The landward limit of surveys along the western shore was the low tide line or the railroad tracks that extend up the west shore of the estuary whichever is most eastward on a given line of latitude except for tidal portions of tributaries such as the Binnen Kill north of Interstate 90 and Catskill Creek north of Bridge Street. For the purposes of this project the low-tide line will be the line of zero depth relative to mean lower low water (MLLW) depicted on NOAA charts 12347 and 12348.