Christopher C. Bemelmans Chelsea A. Stalk Daniel J. Ciarletta Jennifer L. Miselis 20250513 tabular digital data, raster digital data Christopher C. Bemelmans Chelsea A. Stalk Daniel J. Ciarletta Jennifer L. Miselis 20250513 U.S. Geological Survey data release doi:10.5066/P14SGUMT St. Petersburg, Florida U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center https://doi.org/10.5066/P14SGUMT The U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS SPCMSC) collected multibeam echosounder (MBES) bathymetry and sonar backscatter data offshore of Wallops and Assawoman Islands, Virginia in June 2024. This USGS data release includes the corresponding processed MBES-derived elevation points (xyz) and a backscatter mosaic (tag image file format [TIFF]) as part of Field Activity Number (FAN) 2024-310-FA. MBES and backscatter data were acquired using two Teledyne Reason SeaBat T50-P MBES in a dual-head configuration. Additionally, nearshore single-beam echosounder (SBES) and land topographic elevations, as well as Chirp seismic data, were concurrently collected as a part of FAN 2024-310-FA; those data are available as separate data releases (Lyons and others, 2025; Forde and others, 2025). The purpose of the survey was to map the shoreface morphology of Wallops and Assawoman Islands. These data may be used for assessment of coastal resiliency, erosion hazards, and (or) long-term landscape change. Data were collected during USGS Field Activity Number (FAN) 2024-310-FA. Additional survey and data details are available from the USGS Coastal and Marine Geoscience Data System (CMGDS) at, https://cmgds.marine.usgs.gov/services/activity.php?fan=2024-310-FA. The processed sonar-derived elevation data are provided as American Standard Code for Information Interchange (ASCII) x,y,z point data files. These values are not the individual soundings, but nodes from a 1meter (m) bathymetric grid. The Z value for the node is generated by utilizing a Combined Uncertainty and Bathymetry Estimator (CUBE) surface and has an estimated total value of uncertainty (Calder and Wells, 2007). The bathymetry data were collected and processed in the World Geodetic System of 1984 (WGS84) (G2139 realization) horizontal and vertical datums, and were subsequently transformed using the National Oceanic and Atmospheric Administration's (NOAA) VDatum version 4.7 (v.4.7) transformation software (https://vdatum.noaa.gov/). The XYZ data are provided in: (1) Universal Transverse Mercator World Geodetic System 1984 (UTM-WGS84) in meters for the horizontal and WGS84 ellipsoidal height in meters for the vertical; and (2) Virginia State Plane Coordinate System 1983 (SPCS83) Federal Information Processing Standard (FIPS) 4502 in U.S. survey feet (ft) for the horizontal and North American Vertical Datum 1988 (NAVD88) in U.S. survey feet with respect to GEOID18 for the vertical. Processed backscatter intensity data are provided as a geographic tagged image file format (geoTIFF) raster image mosaic. Raster values represent mean intensity returns as derived from a 1-m grid with nodes that correspond with the bathymetry grid. Intensity values for each node are likewise generated by using a CUBE surface. The raster is provided in (1) Universal Transverse Mercator World Geodetic System 1984 (UTM-WGS84) and (2) Virginia State Plane Coordinate System 1983 (SPCS83) Federal Information Processing Standard (FIPS) 4502 in U.S. survey feet. 20240601 20240613 ground condition Complete None planned -75.70780953 -75.33577660 37.89907796 37.73719362 USGS Metadata Identifier USGS:53fbb1e8-ff3f-40d6-9be1-408d94a6edee ISO 19115 Topic Category oceans elevation location geoscientificInformation imageryBaseMapsEarthCover USGS Thesaurus marine geology marine geophysics geophysics bathymetry multibeam sonar ocean characteristics ocean processes None hydrography seafloor mapping Teledyne Reson T50-P Applanix POS MV Wavemaster II U.S. Geological Survey USGS St. Petersburg Coastal and Marine Science Center SPCMSC Geographic Names Information System (GNIS) State of Virginia Wallops Island None Wallops Island, Virginia Mid-Atlantic Coast None June 2024 No access constraints. Please see 'Distribution Information' for details. These data are marked with a Creative Common CC0 1.0 Universal License. These data are in the public domain and do not have any use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center Electronics Technician (Marine Instrumentation) mailing and physical

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St. Petersburg FL 33701 USA (727) 502-8062 cbemelmans@usgs.gov U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center Microsoft Windows 11 Enterprise (Build 19045.4046); NOAA VDatum (version 4.7); HYPACK®, A Xylem Brand and HYPACK HYSWEEP® (version 2023 Q3); Applanix POSPac MMS (POSPac) software (version 9.1, Service Pack 1); Qimera® (version 2.6.2); Fledermaus Geocoder Toolbox (FMGT) (version 7.11.0) International Hydrographic Organization (IHO) 20191031 Monaco International Hydrographic Organization, Intergovernmental Oceanographic Commission pages 81-83 https://www.gebco.net/data_and_products/gebco_cook_book/ QPS 20210101 Zeist, Netherlands QPS pages 1-473 Jonathan Beaudoin Weston Renoud Tannaz H. Mohammadloo M. Snellen 2018 Sydney, Australia HYDRO18 Conference pages 1-16 https://resolver.tudelft.nl/uuid:17c45da0-a0df-4fee-b419-e6f7b24c8754 Dr. Bruno Scherzinger Joe Hutton 2025 Westminster, Colorado Trimble pages 1-9 https://applanix.trimble.com/en/resources/flipbooks/applanix-in-fusion-plus-the-ultimate-solution-for-enhanced-spatial Brian R. Calder David E. Wells 20070129 Durham, NH University of New Hampshire, Center for Coastal and Ocean Mapping pages 1-54 https://scholars.unh.edu/ccom/1217 International Hydrographic Organization (IHO) 200802 Principaute de Monaco International Hydrographic Bureau pages 1-28 https://iho.int/uploads/user/pubs/standards/s-44/S-44_5E.pdf Erin O. Lyons Julie C. Bernier Sydney K. Nick Daniel J. Ciarletta Jennifer L. Miselis 20250513 U.S. Geological Survey data release doi:10.5066/P1HFYGE6 St. Petersburg, Florida U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center https://doi.org/10.5066/P1HFYGE6 Arnell S. Forde Chelsea A. Stalk Daniel J. Ciarletta Jennifer L. Miselis 20250318 U.S. Geological Survey data release doi:10.5066/P1NZ6CC2 St. Petersburg, Florida U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center https://doi.org/10.5066/P1NZ6CC2 This dataset was from a single research cruise with exact instrumentation and set up and is therefore internally consistent. Methods were employed to maintain data collection consistency aboard the platform. During mobilization, each piece of equipment was isolated to obtain internal and external offset measurements with respect to the survey platform. All the critical measurements were recorded manually and digitally entered into their respective programs. These files represent the post-processed bathymetric data (x,y,z) during a multibeam bathymetry survey. These are complete post-processed x,y,z bathymetric data points from multibeam data collected nearshore Wallops and Assawoman Islands, Virginia, June, 2024. All data were collected and processed to meet or exceed International Hydrographic Organization (IHO) Special Order standards for positioning and depth (IHO, 2008). CUBE Uncertainty values associated with each node are available in the x,y,z file, with a mean value of 0.05 m. All data were collected and processed to meet or exceed IHO Special Order standards for positioning and depth (IHO, 2008). CUBE Uncertainty values associated with each node are available in the x,y,z file, with a mean value of 0.05 m. Data transformed using VDatum have an additional reported vertical transformation error of 3.70237 centimeters (cm) or 0.1214686 US survey ft. Acquisition: An Ellipsoidally Referenced Survey (ERS) consisting of multibeam bathymetry was conducted using two Teledyne Reson SeaBat T50-P multibeam echosounders, in dual-head configuration. The pair of Mills Cross (configuration) transmit and receive arrays, were placed side-by-side within a bracket that oriented them at opposing 30-degree angles (relative to horizontal). The bracket was pole-mounted on the starboard gunnel of the Research Vessel (R/V) Sallenger, a 26-foot fiberglass vessel. The sonar arrays were oriented athwartships (primary and secondary arrays facing outward and down to port and starboard, respectively) and located approximately 1-m below the waterline when deployed. An Applanix Pos MV Wavemaster II V5 inertially aided navigation system was used for timing, positioning, and attitude. The Inertial Measurement Unit (IMU) was mounted atop the sonar bracket just aft of the pole. Two Trimble GA830 Global Navigation Satellite System (GNSS) antennas were affixed atop the cabin approximately amidships of the vessel, two meters apart, port-starboard. An AML Oceanographic Micro-X sound velocity sensor was used for speed of sound readings at the sonar head. A Sontek CastAway CTD was used for measuring sound velocity profiles. Hydrographic survey acquisition and processing software, HYPACK® and HYPACK HYSWEEP® (version 2023 Q3) managed data inputs from sensors and produced two files (.RAW and .HSX). Data were collected in WGS84 (G2139) Universal Transverse Mercator (UTM) Zone 18 North (18N) coordinates. 20240613 Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center mailing and physical

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St. Petersburg FL 33701 USA (727) 502-8062 cbemelmans@usgs.gov Processing: Positioning and attitude data were post-processed in Applanix POSPac MMS (POSPac) software version 9.1 Service Pack 1. Raw position files were imported into POSPac and processed with the IN-Fusion PP-RTX processing mode utilizing Trimble CenterPoint RTX technology (Scherzinger and Hutton, 2025), creating smoothed best estimate of trajectory (SBET) files and dynamic error files (SMRMSG) for each day of the survey. Bathymetric data were post-processed in Qimera® Hydrographic processing software version 2.6.2. HYPACK® acquisition files (.HSX) were first imported into Qimera® and then post-processed navigation files (SBET and SMRMSG) were imported and applied. Additionally, Global Positioning System (GPS) tide (GPS tidal corrections utilize GPS height information from real time survey observations to obtain an ellipsoid height) was computed and sound velocity profiles were applied (IHO, 2019). Roll calibration was also performed, as necessary, and values were applied to the data (QPS, 2021). CUBE Uncertainty “layer reflects the standard deviation, scaled to 95% confidence level, of the accepted soundings that contributed to the selected hypothesis.” (QPS, 2021). Data were filtered to exclude any points with RESON Quality flags of 0, 1, and 2 (these flags are assigned to individual soundings at the time of acquisition and are a metric of pass/fail in regard to both brightness and collinearity: 0 = fail both, 1 = pass brightness only, 2 = pass collinearity only), as well as soundings that had a Total Propagated Uncertainty (TPU) greater than stated IHO Special Order standards (IHO, 2008). Refraction artifacts were addressed automatically using the Technical University of Delft (TU Delft) sound-speed inversion tool (Beaudoin and others, 2018) and manually using the Refraction Editor filter. Further manual editing of data points that deviated significantly from the surrounding surface was performed in Slice Editor (QPS, 2021) and a 1-m bathymetric CUBE surface was computed (Calder and Wells, 2007). Small gaps in the continuous surface were caused by limitations in swath width and planned line navigation within shallow waters. Large data gaps in the southern portion of the survey were the result of a 65-degree beam angle filter applied to this section to remove erroneous data. The final surface was exported as an x,y,z ASCII file using the Dynamic CUBE Surface to ASCII function. 2024 2024-310-FA_MBES_Wallops_1m_WGS84_UTM18N.xyz Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center mailing and physical

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St. Petersburg FL 33701 USA (727) 502-8062 cbemelmans@usgs.gov Backscatter Mosaic Creation: Acoustic Intensity Backscatter data were extracted from HSX files in Qimera® Hydrographic processing software version 2.6.2. The final CUBE bathymetry surface serves as input for geometric corrections, and average temperature and salinity data (derived from the Sontek CastAway CTD measurements taken during acquisition) are utilized by the program to calculate local absorption and transmission loss. GSF files were exported from Qimera® and imported into FMGT for backscatter mosaic creation. These inputs, along with the following settings were entered into FMGT, and then processing was initiated [Weighted Average = blending, image type = beam average, weighting = swath, and an Angle-Varying gain = 200]. During processing, the tool automatically creates a pattern file (.bbp) which is used to correct for variations in the beam pattern of the system (QPS, 2021). Upon completion, a 1-m backscatter mosaic with intensity values ranging from 9.6875 to -65.625 dB (decibels) was created, and the mosaic was exported as a 32-bit floating point GeoTIFF (.tiff) using the 'Export Floating Point GeoTIFF' function. 2024 2024-310-FA_Wallops_MBES_1m_Backscatter.tiff Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center mailing and physical

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St. Petersburg FL 33701 USA (727) 502-8062 cbemelmans@usgs.gov Datum Transformation: Final x,y,z data were converted using NOAA's VDatum v.4.7 software conversion tool from the WGS84 [G2139] realization, in meters, to NAD83 [2011] Virginia South State Plane Coordinate System NAVD88, in US survey feet, using the GEOID18 model (orthometric height). 2025 2024-310-FA_MBES_Wallops_1m_NAD83_NAVD88_VAStatePlane_USSFT.txt Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center mailing and physical

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St. Petersburg FL 33701 USA (727) 502-8062 cbemelmans@usgs.gov Point Point 34649380 Universal Transverse Mercator 18 0.999600 -87.000000 0.0 500000.0 0.0 coordinate pair 0.6096 0.6096 meters World Geodetic System of 1984 WGS_84 6378137.0 298.257223563 World Geodetic System of 1984 0.001 meters Attribute values 2024-310-FA_MBES_Wallops_1m_WGS84_UTM18N.xyz ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in the WGS84 [G2139] realization (ellipsoid height). HYPACK® WGS84_18_X WGS84 UTM Zone 18N X-coordinate (easting) of sample point, in meters. HYPACK® 453332.500 464689.500 0.001 WGS84_18_Y WGS84 UTM Zone 18N Y-coordinate (northing) of sample point, in meters. HYPACK® 4178775.500 4194493.500 0.001 WGS84_Z WGS84 (ellipsoid height) of sample point, in meters. HYPACK® -51.96 -39.60 0.01 Uncertainty CUBE Uncertainty, in meters. Qimera® 0.000000 0.575153 0.000001 2024-310-FA_MBES_Wallops_1m_NAD83_NAVD88_VAStatePlane_USSFT.txt ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in NAD83 [2011], NAVD88, Virginia South State Plane Coordinate System, in US survey feet, which were derived using the GEOID18 model (orthometric height). VDatum NAD83_SP_X NAD83 Virginia South State Plane Coordinate System X-coordinate (easting) of sample point, in US survey ft. VDatum 12341377.40709 12377521.46210 0.00001 NAD83_SP_Y NAD83 Virginia South State Plane Coordinate System Y-coordinate (northing) of sample point, in US survey ft. VDatum 3812248.84202 3864885.75118 0.00001 NAVD88_Z NAVD88 (orthometric height) Virginia South State Plane Coordinate System of sample point, in US survey ft. VDatum -46.07930 -5.44290 0.00001 Uncertainty CUBE Uncertainty, in meters, as reported for WGS84 (G2139) data. A static uncertainty value of 0.1214686 US survey feet is associated with the transformation of this data. Qimera® 0.000000 0.575153 0.000001 U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center USGS SPCMSC Data Management mailing and physical

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Saint Petersburg FL 33701 United States 727-502-8000 gs-g-spcmsc_data_inquiries@usgs.gov 2024-310-FA_MBES_Wallops_1m_WGS84_UTM18N.xyz, 2024-310-FA_MBES_Wallops_1m_NAD83_NAVD88_VAStatePlane_USSFT.txt, 2024-310-FA_Wallops_MBES_1m_Backscatter.tiff Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. columnar text, GeoTIFF ZIP 1943 https://coastal.er.usgs.gov/data-release/doi-P14SGUMT/data/Wallops_2024_MBES_xyz.zip https://coastal.er.usgs.gov/data-release/doi-P14SGUMT/data/Wallops_2024_MBES_Backscatter.zip None 20250513 U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center USGS SPCMSC Data Management mailing and physical

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Saint Petersburg FL 33701 United States 727-502-8000 gs-g-spcmsc_data_inquiries@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998