Stevens, A.W., Lacy, J.R., Finlayson, D.P., and Gelfenbaum, G. 2008 tabular digital data Stevens, A.W., Lacy, J.R., Finlayson, D.P., and Gelfenbaum, G. 2008 Scientific Investigations Report 2008-5009 Menlo Park, CA U.S. Geological Survey, Coastal and Marine Geology Program http://pubs.usgs.gov/sir/2008/5009/ Nearshore bathymetry and seagrass cover at two sites in northern Puget Sound were mapped with single-beam sonar and an underwater video. Acoustic data were compared against underwater video data collected simultaneously to better understand the accuracy, limitations and benefits of mapping seagrass acoustically in Puget Sound. The goal of the project was two-fold: 1) To quantify eelgrass (Z. marina) habitat at two sites, Possession Point and Browns Bay, in northern Puget Sound and 2) Evaluate the benefits and limitations of using acoustics, specifically single-beam sonar, to map seagrass in Puget Sound. To map seagrass at two sites in northern Puget Sound, a dual-frequency Biosonics sonar operating at 200 and 430 kHz was used to map seafloor depth, morphology and vegetation. An underwater video camera was deployed to ground-truth acoustic data. Fifty one sediment samples were collected to quantify sediment grain size distributions across Possession Point. Sediment samples were analyzed for grain size at the Western Coastal and Marine Geology Team sediment laboratory in Menlo Park, CA. 20070130 20070202 ground condition Complete None planned -123.17290 -123.13793 48.60642 48.58775 General U.S. Geological Survey USGS Coastal and Marine Geology Program CMGP bathymetry seagrass sediment oceans and estuaries ISO 19115 Topic Category geoscientificinformation location oceans inlandWaters elevation Global Change Master Directory (GCMD) Earth Science > Oceans > Bathymetry/Seafloor Topography Earth Science > Oceans > Coastal Processes Earth Science > Oceans > Marine Sediments Instruments > Grab Samplers General WA USA Geographic Names Information System (GNIS) Possession Point Browns Bay Puget Sound Washington None Public domain data from the U.S. government is freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information. Andrew Stevens U.S. Geological Survey, Coastal and Marine Geology Oceanographer mailing and physical address

345 Middlefield R. MS999

Menlo Park CA 94025-3561 USA (650) 329-5243 (650) 329-5190 astevens@usgs.gov http://walrus.wr.usgs.gov/infobank/b/b207ps/html/b-2-07-ps.meta.html Index map of field activity B-2-07-PS. GIF U.S. Geological Survey, Coastal and Marine Geology Program 2007 http://walrus.wr.usgs.gov/infobank/b/b207ps/html/b-2-07-ps.meta.html A) Bathymetric mapping A) Bathymetric mapping Sixty (60) kilometers of acoustic bathymetry/substrate data were collected with a dual-frequency (200 and 430 kHz) Biosonics system along 163 transects in Possession Point between 1/30/07 and 2/1/07. Eighteen(18) kilometers of acoustic bathymetry/substrate data were collected with the same system along 65 transects in Browns Bay on 2/2/2007. The Biosonics sonar generates a 6-degree cone of sound, which translates into a footprint on the seafloor ranging 0.55 to 55 m^2 area for the water depths surveyed (2 - 20 m). Ship speed generally ranged 4.0-4.5 kts and data were merged with GPS positions at 1 Hz. Track lines were spaced 25 - 50 m apart. B) Sediment Samples for Grain Size Analyses Sediment samples were collected using a van veen grab sampler or taken directly during low-tide surveys. In the field, a sub-sample of the uppermost 1-3 cm of each grab was collected and placed into storage bags, labeled, and logged. Samples were disaggregated and sieved through 2000 and 62 micron screens to separate gravel, sands and mud after the organic component was removed by treatment with hydrogen peroxide. Sediment grain size of sands was determined using the settling methods and principles of Stokes Law on the USGS 3-m long settling tubes. The fine fraction (silts and clays) were analyzed on a Coulter 230 Laser Particle Analyzer. Three samples had less than 3% intermediate fraction and were analyzed on the Coulter. Single sample runs were made on the tubes, while results from the laser particle analyzer are averages of triplicates with standard deviations around the mean ranging 18 to 24 microns due to instrument errors. A) Bathymetric mapping The combined bathymetric data were merged to create a digital elevation model representing the surface topography of Possession Point and Browns Bay. This surface is referenced to the NAD83 datum in the WA State Plane North, meters projection with a horizontal accuracy of 2.3 cm. Elevations are referenced to NAVD88 with an estimated vertical accuracy ranging 2.6-9.8 cm. This includes error from the RTK-DGPS and Biosonics sonar, and errors introduced in data processing. 2007 B) Sediment Samples for Grain Size Analyses Results from the tubes and laser particle analyzer were merged using standard USGS methods found in the USGS particle analysis program pcSedSize. 2007 Point 0.00001 0.00001 Decimal degrees North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 North American Vertical Datum of 1988 0.1 meters Explicit elevation coordinate included with horizontal coordinates local surface 0.1 meters Explicit depth coordinate included with horizontal coordinates line[number].xyz digital surface elevation data USGS X Location X-coordinate of the data point. USGS 486997.617 489962.263 meters 0.001 Y Location Y-coordinate of the data point. USGS 5381456.319 5383932.558 meters 0.001 Z Location Z-coordinate of the data point. USGS -10.00 0.00 meters 0.01 sediment grain size data surface elevation data USGS Lon Location X-coordinate of the data point. USGS -123.58611 -123.13611 decimal degrees 0.00001 Lat Location Y-coordinate of the data point. USGS 48.58611 48.60833 decimal degrees 0.00001 Depth_m Location Z-coordinate of the data point. USGS 0.00 10.00 meters 0.01 >Sample of digital surface elevation data XYZ ASCII file, bathy/line95.xyz: >X Y Z >487989.879521 5381998.198351 -3.31 >487990.116289 5381998.892258 -3.34 >487989.943243 5382001.029467 -3.40 > >Sample of sediment sampling log: >Station Local_Time UTC Lon Lat Depth_m Comment >1 6/1/07 20:44 6/2/07 3:44 -123.1430877 48.60642247 2.286 - >2 6/1/07 20:35 6/2/07 3:35 -123.1416559 48.60596625 2.1336 18.6 C >3 6/1/07 20:28 6/2/07 3:28 -123.1396819 48.60476647 2.4384 22.4 C none U.S. Geological Survey, Coastal and Marine Geology Andrew Stevens Oceanographer mailing and physical address

345 Middlefield Rd. MS999

Menlo Park CA 94025-3561 USA (650) 329-5243 (650) 329-5190 astevens@usgs.gov Although this data set has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20080212 U.S. Geological Survey, Coastal and Marine Geology Andrew Stevens Oceanographer mailing and physical address

345 Middlefield Rd. MS999

Menlo Park CA 94025-3561 USA (650) 329-5243 (650) 329-5190 astevens@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998