Chelsea A. Stalk Christopher C. Bemelmans Jennifer L. Miselis 20250325 raster digital data, tabular digital data Chelsea A. Stalk Christopher C. Bemelmans Jennifer L. Miselis 20250325 U.S. Geological Survey data release doi:10.5066/P1NWHXZS St. Petersburg, Florida U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center https://doi.org/10.5066/P1NWHXZS An Ellipsoidally Referenced Survey (ERS) using two Teledyne Reson SeaBat T50-P multibeam echosounders, in dual-head configuration, was conducted by the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center (SPCMSC) covering the nearshore areas around the Chandeleur Islands, Louisiana (LA), during 2 survey legs: June 12-21 and July 31-August 11, 2023. The download file, Chandeleur_Islands_2023_MBES_xyz.zip, includes processed elevation point data (x,y,z), as derived from a 1-meter (m) bathymetric grid. The download file, Chandeleur_Islands_2023_MBES_Backscatter.zip, includes acoustic backscatter intensity data in 32-bit floating point GeoTIFF (Geographic Tagged Image File Format, .tiff) format. The purpose of this study was to conduct a morphologic and geologic assessment of the impacts of the 2020 and 2021 hurricane seasons within part of the Breton National Wildlife Refuge. With data from previous surveys, these data will be used to quantify sediment redistribution. Data were collected during USGS Field Activity Number (FAN) 2023-325-FA. Single-beam bathymetry data and seismic reflection data were acquired as a part of the same field activity, refer to Lyons and others (2025) and Forde and others (2024), respectively, for further details. 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=2023-325-FA. Seismic data were also acquired as a part of this field activity, please refer to Forde and others (2024) for further details. The processed sonar 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 1-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) (G1150 realization) horizontal and vertical datums, and were subsequently transformed using the National Oceanic and Atmospheric Administration's (NOAA) VDatum version 4.2.2 (v.4.2.2) transformation software (https://vdatum.noaa.gov/) horizontally to the North American Datum of 1983 (NAD83 [2011]) and vertically to the North American Vertical Datum of 1988 (NAVD88) relative to the GEOID model of 2018 (GEOID18). 20230612 20230811 ground condition Complete None planned -89.18871485 -89.09223983 29.48448296 29.09223983 USGS Metadata Identifier USGS:45cf2584-078d-427c-aec3-11f02f61a87e 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 Louisiana Chandeleur Islands Hewes Point None Chandeleur Islands, Louisiana Mid-Gulf Coast None June - August 2023 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

600 4th Street South

St. Petersburg FL 33701 USA (727)502-8000 cbemelmans@usgs.gov U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center Microsoft Windows 10 Version 622H2 (Build 19045.4046); NOAA VDatum (version 4.2.2); HYPACK®, A Xylem Brand and HYPACK HYSWEEP® (version 22.3.1.0); Applanix POSPac MMS (POSPac) software (version 8.8, Service Pack 1); Teledyne CARIS™ Hydrographic processing software HIPS and SIPS (version 11.4.28). 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/ Caris 20150601 Fredericton, NB, Canada Caris pages 1-446 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 4, quai Antoine 1er B.P. 445 - MC 98011 MONACO Cedex 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 Chelsea A. Stalk Jennifer L. Miselis Noreen A. Buster Julie C. Bernier Nancy T. DeWitt 20250325 U.S. Geological Survey data release doi:10.5066/P1HJAVAR St. Petersburg, Florida U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center https://doi.org/10.5066/P1HJAVAR Arnell S. Forde Jennifer L. Miselis Chelsea A. Stalk Noreen A. Buster 20240515 U.S. Geological Survey data release doi:10.5066/P1HOLGKM St. Petersburg, Florida U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center https://doi.org/10.5066/P1HOLGKM This dataset was from a single field effort with two survey legs, each with exact instrumentation and set up and were 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 (x,y,z) and acoustic intensity (dB) data during a multibeam bathymetry survey. These data are the complete, post-processed x,y,z bathymetric and backscatter data points from multibeam data collected nearshore the Chandeleur Islands, Louisiana, June-August, 2023. All data were collected and processed to meet or exceed International Hydrographic Organization (IHO) Special Order standards for positioning and depth (IHO, 2008). Individual Total Propagated Uncertainty (TPU) values associated with each node are available in the x,y,z file, with a mean value of 0.056 m. All data were collected and processed to meet or exceed IHO Special Order standards for positioning and depth (IHO, 2008). Individual TPU values associated with each node are available in the x,y,z file, with a mean value of 0.067 m. Data transformed using Vdatum have an additional reported vertical transformation error of 0.065 meters (m). Acquisition: An 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 22.3.1.0) managed data inputs from sensors and produced two files (.RAW and .HSX). Data were collected in WGS84 (G1150) Universal Transverse Mercator (UTM) Zone 16 North (16N) coordinates. Multibeam and backscatter data were collected in three areas: to the east of Hewes Point (referred to as 'MainAOI'), a portion of the single-beam survey coverage (Lyons and others, 2025) north and west of Hewes Point ('SBESCoverage'), and offshore of the southernmost Chandeleur Islands ('SouthernRecon'). Multibeam coverage was extended outside of the main AOI to ensure complete coverage of the survey area during the survey period (west, single-beam survey) and to support geophysical data collection (SouthernRecon). 20230811 Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center mailing and physical

600 4th Street South

St. Petersburg FL 33701 USA (727) 502-8000 cbemelmans@usgs.gov Processing: Positioning and attitude data were post-processed in Applanix POSPac MMS (POSPac) software version 8.8 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 Teledyne CARIS™ Hydrographic processing software HIPS and SIPS version 11.4.28. HYPACK® acquisition files (.HSX) were first imported into CARIS™ and then post-processed navigation files (SBET and SMRMSG) were imported and applied (Caris, 2015). Additionally, Global Positioning System (GPS) tide (GPS tidal corrections utilize GPS height information from real time survey observations to obtain an ellipsoid height) were applied (IHO, 2019). Sound Velocity Profiles (SVPs) were edited in the SVP editor where all observations from the water line to the sonar heads (1 m water depth) were rejected along with any outlying data. After editing, the SVPs were applied to the sounding data. Roll calibration was also performed, as necessary. TPU was calculated from real time values recorded in the HSX and the SMRMSG files (IHO, 2019). 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 TPU greater than stated IHO Special Order standards (IHO, 2008). Refraction artifacts were addressed using Refraction Editor. Further editing was performed in Subset Editor. A 1-m bathymetric CUBE surface was computed and a visual and statistical inspection of the data effecting the surface was performed and edited as needed to serve as quality control (Calder and Wells, 2007). Gaps in the continuous surface were caused by limitations in swath width and planned line navigation within shallow waters. The final surface was exported as an x,y,z ASCII file using the Base Surface to ASCII function. 2023 2023_325_Chandeleurs_MBES_MainAOI_1m_WGS84_UTM16N.xyz 2023_325_Chandeleurs_MBES_SBESCoverage_1m_WGS84_UTM16N.xyz 2023_325_Chandeleurs_MBES_SouthernRecon_1m_WGS84_UTM16N.xyz Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center mailing and physical

600 4th Street South

St. Petersburg FL 33701 USA (727) 502-8000 cbemelmans@usgs.gov Acoustic Intensity Backscatter data (.7k) were loaded in CARIS Hydrographic processing software HIPS/SIPS version 11.4.28 using the SIPS Backscatter tool. 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. These inputs, along with the following settings were entered into the tool, 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. Upon completion, a 1-m backscatter mosaic with intensity values ranging from -17.63 to 3.156 dB (decibels) was created for each survey area. After visual inspection, the mosaic was exported as a 32-bit float GeoTIFF (.tiff) using the surface to GeoTIFF function. 2023 2023_325_Chandeleurs_MBES_MainAOI_1m_Backscatter.tiff 2023_325_Chandeleurs_MBES_SBESCoverage_1m_Backscatter.tiff 2023_325_Chandeleurs_MBES_SouthernRecon_1m_Backscatter.tiff Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center mailing and physical

600 4th Street South

St. Petersburg FL 33701 USA (727) 502-8000 cbemelmans@usgs.gov Datum Transformation: Final x,y,z data were converted using NOAA's VDatum v.4.2.2 software conversion tool from the WGS84 [G1150] realization to NAD83 [2011] NAVD88, using the GEOID18 model (orthometric height). 2023 2023_325_Chandeleurs_MBES_MainAOI_1m_NAD83_NAVD88_G18.xyz 2023_325_Chandeleurs_MBES_SBESCoverage_1m_NAD83_NAVD88_G18.xyz 2023_325_Chandeleurs_MBES_SouthernRecon_1m_NAD83_NAVD88_G18.xyz Christopher C. Bemelmans U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center mailing and physical

600 4th Street South

St. Petersburg FL 33701 USA (727) 502-8000 cstalk@usgs.gov Point Point 45,543,457 Universal Transverse Mercator 16 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 2023_325_Chandeleurs_MBES_MainAOI_1m_WGS84_UTM16N.xyz ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in the WGS84 [G1150] realization (ellipsoid height) of the main area of interest (AOI), east of Hewes Point. HYPACK® WGS84_UTM16N_X WGS84 UTM Zone 16N X-coordinate (easting) of sample point, in meters. HYPACK® 318941.000 326520.000 0.001 WGS84_UTM16N_Y WGS84 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. HYPACK® 3313791.000 3329030.000 0.001 WGS84_Z WGS84 (ellipsoid height) of sample point, in meters. HYPACK® -39.292 -30.016 0.001 TPU TPU = Total Propagated Uncertainty, in meters. Teledyne CARIS™ 0.040 0.260 0.001 2023_325_Chandeleurs_MBES_SBESCoverage_1m_WGS84_UTM16N.xyz ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in the WGS84 [G1150] realization (ellipsoid height) of a portion of the single-beam (SBES) survey coverage (Lyons and others, 2025) north and west of Hewes Point. HYPACK® WGS84_UTM16N_X WGS84 UTM Zone 16N X-coordinate (easting) of sample point, in meters. HYPACK® 314182.000 319686.000 0.001 WGS84_UTM16N_Y WGS84 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. HYPACK® 3319827.000 3328890.000 0.001 WGS84_Ellipsoid_Z WGS84 (ellipsoid height) of sample point, in meters. HYPACK® -37.477 -32.290 0.001 TPU TPU = Total Propagated Uncertainty, in meters. Teledyne CARIS™ 0.040 0.256 0.001 2023_325_Chandeleurs_MBES_SouthernRecon_1m_WGS84_UTM16N.xyz ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in the WGS84 [G1150] realization (ellipsoid height) offshore of the southernmost Chandeleur Islands. HYPACK® WGS84_UTM16N_X WGS84 UTM Zone 16N X-coordinate (easting) of sample point, in meters. HYPACK® 316450.000 322444.000 0.001 WGS84_UTM16N_Y WGS84 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. HYPACK® 3291078.000 3299262.000 0.001 WGS84_Ellipsoid_Z WGS84 (ellipsoid height) of sample point, in meters. HYPACK® -34.787 -29.487 0.001 TPU TPU = Total Propagated Uncertainty, in meters. Teledyne CARIS™ 0.040 0.220 0.001 2023_325_Chandeleurs_MBES_MainAOI_1m_NAD83_NAVD88_G18.xyz ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in NAD83 [2011], NAVD88, which were derived using the GEOID18 model (orthometric height) of the main area of interest (AOI), east of Hewes Point. VDatum NAD83_UTM16N_X NAD83 UTM Zone 16N X-coordinate (easting) of sample point, in meters. VDatum 318941.85794 326520.85528 0.00001 NAD83_UTM16N_Y NAD83 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. VDatum 3313790.42426 3326029.42104 0.00001 NAVD88_GEOID18_Z NAVD88 (orthometric height) of sample point, in meters, with respect to GEOID12B. VDatum -10.962 -2.020 0.001 TPU_WGS84 Total Propagated Uncertainty, in meters, as reported for WGS84 (G1150) data. A static uncertainty value of 0.065 meters (m) is associated with the transformation of this data. Teledyne CARIS™ 0.040 0.220 0.001 2023_325_Chandeleurs_MBES_SBESCoverage_1m_NAD83_NAVD88_G18.xyz ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in NAD83 [2011], NAVD88, which were derived using the GEOID18 model (orthometric height) a portion of the single-beam survey (SBES) coverage (Lyons and others, 2025) north and west of Hewes Point. VDatum NAD83_UTM16N_X NAD83 UTM Zone 16N X-coordinate (easting) of sample point, in meters. VDatum 314182.85875 319686.85782 0.00001 NAD83_UTM16N_Y NAD83 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. VDatum 3319826.42345 3328889.42131 0.00001 NAVD88_GEOID18_Z NAVD88 (orthometric height) of sample point, in meters, with respect to GEOID12B. VDatum -9.170 -4.019 0.001 TPU_WGS84 Total Propagated Uncertainty, in meters, as reported for WGS84 (G1150) data. A static uncertainty value of 0.065 meters (m) is associated with the transformation of this data. Teledyne CARIS™ 0.040 0.260 0.001 2023_325_Chandeleurs_MBES_SouthernRecon_1m_NAD83_NAVD88_G18.xyz ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in NAD83 [2011], NAVD88, which were derived using the GEOID18 model (orthometric height) offshore of the southernmost Chandeleur Islands. VDatum NAD83_UTM16N_X NAD83 UTM Zone 16N X-coordinate (easting) of sample point, in meters. VDatum 316450.85608 322444.85513 0.00001 NAD83_UTM16N_Y NAD83 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. VDatum 3291077.42993 3299261.42785 0.00001 NAVD88_GEOID18_Z NAVD88 (orthometric height) of sample point, in meters, with respect to GEOID12B. VDatum -7.709 -2.251 0.001 TPU_WGS84 Total Propagated Uncertainty, in meters, as reported for WGS84 (G1150) data. A static uncertainty value of 0.065 meters (m) is associated with the transformation of this data. Teledyne CARIS™ 0.040 0.220 0.001 2023_325_Chandeleurs_MBES_MainAOI_1m_Backscatter.tiff, 2023_325_Chandeleurs_MBES_SBESCoverage_1m_Backscatter.tiff, 2023_325_Chandeleurs_MBES_SouthernRecon_1m_Backscatter.tiff: Datasets are GeoTIFFs included in the download file, Chandeleur_Islands_2023_MBES_Backscatter.zip, which is acoustic backscatter intensity data in 32-bit floating point GeoTIFF (.tiff) format with 21229 columns and 19507 rows (min/max [decibels] of -60.21 to 16.8055), 20920 columns and 13168 rows (min/max [decibels] of -45.65 to 18.74), 22452 columns and 12504 rows (min/max [decibels] of -64.91 to 18.7297), respectively. Dataset is projected to the WGS 1984 UTM Zone 18N coordinate system. Backscatter data were collected in three areas: to the east of Hewes Point (referred to as 'MainAOI'), a portion of the single-beam survey coverage (Lyons and others, 2025) north and west of Hewes Point ('SBESCoverage'), and offshore of the southernmost Chandeleur Islands ('SouthernRecon'). The entity and attribute information were generated by the individual and/or agency identified as the originator of the dataset. Please review the rest of the metadata record for additional details and information. U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center USGS SPCMSC Data Management mailing and physical

600 4th Street South

Saint Petersburg FL 33701 United States 727-502-8000 gs-g-spcmsc_data_inquiries@usgs.gov 2023_325_Chandeleurs_MBES_MainAOI_1m_WGS84_UTM16N.xyz, 2023_325_Chandeleurs_MBES_MainAOI_1m_NAD83_NAVD88_G18.xyz, 2023_325_Chandeleurs_MBES_MainAOI_1m_Backscatter.tiff, 2023_325_Chandeleurs_MBES_SBESCoverage_1m_WGS84_UTM16N.xyz, 2023_325_Chandeleurs_MBES_SBESCoverage_1m_NAD83_NAVD88_G18.xyz, 2023_325_Chandeleurs_MBES_SBESCoverage_1m_Backscatter.tiff, 2023_325_Chandeleurs_MBES_SouthernRecon_1m_WGS84_UTM16N.xyz, 2023_325_Chandeleurs_MBES_SouthernRecon_1m_NAD83_NAVD88_G18.xyz, 2023_325_Chandeleurs_MBES_SouthernRecon_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 160 https://coastal.er.usgs.gov/data-release/doi-P1NWHXZS/data/Chandeleur_Islands_2023_MBES_xyz.zip https://coastal.er.usgs.gov/data-release/doi-P1NWHXZS/data/Chandeleur_Islands_2023_MBES_Backscatter.zip None 20250324 U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center USGS SPCMSC Data Management mailing and physical

600 4th Street South

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