Hudson River Sub_Bottom Profile Data - Raw SEG-Y Files (*.sgy)

Hudson River Estuary Shallow Water Surveys. Subbottom data was collected November 5 to December 15, 2009, in the estuary north from Saugerties to Troy. Data Collection and Processing: Subbottom Data - Fugro utilized the EdgeTech SB216 Chirp subbottom profiler system for seismic data collection. This system was operated using a swept frequency range of 2-16 KHz, maximizing subsurface resolution within the very shallow near-surface material (1- 5 m beneath seafloor). Subbottom data was processed and interpreted using Discover and SMT Kingdom software. The intent of the processing was to provide the NYSDEC with SEG-Y files that were properly filtered and spatially oriented to allow for near-surface interpretation of sediments in the Hudson River. Processing steps for the subbottom data included swell filtering to compensate for sea conditions during survey operations, compiling correct shotpoint navigation, and adjusting data gains for optimal interpretation. An isopach (sediment thickness) of the unconsolidated surficial sediments was created from the seafloor and mapped sediment horizon base using an acoustic two-way travel time of 1500 meters/second. Subbottom data was used to assist in selecting sediment sampling locations. Graphical sub-bottom profiles for areas of interest were produced and descriptive results will be included in the final report. Points were created every 300th shot (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 was the line of zero depth relative to mean lower low water (MLLW) depicted on NOAA charts 12347 and 12348. The EdgeTech FS-SB subbottom profiler deployed during survey operations operated at a swept frequency range of 2-16 kHz. However, a transducer ping rate of 6-8 Hz (depending on water depths) corresponded to a hardware-applied data sampling interval of 40 microseconds. A built in anti-alias filter ensured a recorded frequency cut-off of 12 kHz. This is the maximum frequency that can be sampled at 40 microseconds, ensuring that no higher frequency events (above 12kHz) are aliased as a lower frequency event in the data. Given that high frequency events tend to rapidly attenuate in the water column and immediate subsurface, the lack of recorded frequencies above 12 kHz does not adversely impact data resolution (.02 meters estimated resolution for 16 kHz and .03 meters for 12 kHz) or subsurface mapping capabilities given the system's stated overall resolution (incorporating lower frequencies toward 2 kHz) of .1 meter.

Sub bottom profile trace header data in SEG-Y format

Fugro

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Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.3.0.1770

Data are geo-referenced using differential GPS (DGPS) which results in a lateral accuracy of <+/-1 meter.

The data covers the area of the estuary north from Saugerties to Troy in areas of shallow water (defined as any part of the estuary covered by water at low tide and shallower than 5 meters relative to NAVD88. For the purposes of this project the low-tide line was the line of zero depth relative to mean lower low water (MLLW) depicted on NOAA charts 12347 and 12348.

Fugro utilized the EdgeTech SB216 Chirp subbottom profiler system for seismic data collection. This system was operated using a swept frequency range of 2-16 KHz, maximizing subsurface resolution within the very shallow near-surface material (1- 5 m beneath seafloor). Position of the device was determined every second. After acquisition, navigation data was examined for outliers and applied to the subbottom profiler data to ensure proper positioning in the spatial domain.