Ann E. Gibbs Anita C. Engelstad Jin-Si R. Over Richard M. Buzard Alexander G. Snyder Alexander L. Nereson 20260313 comma-delimited text data release DOI:10.5066/P13YIWKC Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey https://doi.org/10.5066/P13YIWKC Li Erikson Ann E. Gibbs Richard M. Buzard Daniel J. Nowacki Alexander G. Snyder Anita C. Engelstad Cordell Johnson Alexander L. Nereson Jin-Si R. Over Paul Russel Colin Lyons 2025 data release DOI:10.5066/P13YIWKC Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey Suggested Citation: Erikson L.H., Gibbs A.E., Buzard R.M., Nowacki D.J., Snyder A.G., Engelstad A.C., Johnson C., Nereson A.L., Over J.R., Russel, P., Lyons, C., 2025, In situ field data, Coastal Alaska 2023 to 2025 (ver. 2.0, March 2026): U.S. Geological Survey data release, https://doi.org/10.5066/P13YIWKC. https://doi.org/10.5066/P13YIWKC This dataset contains nearshore and inland bathymetry near Kotzebue, Alaska. The data were collected on July 10, 2024, and subsequently processed by the U.S. Geological Survey, Pacific Coastal and Marine Science Center. Results are provided in a comma-separated value format (csv). This product was created to advance coastal storm response and recovery in Alaskan coastal communities in the wake of the September 2022 extratropical Typhoon Merbok disaster. It is being used by the USGS to support the development of dynamic flood models for more than 20 communities along the northwest coasts of Alaska. This product is intended for reuse by scientists, managers, and the general public. These data can be opened with any text viewer, spreadsheet editor, or geographic information systems (GIS) software for review, visualization, and analysis purposes. Work was funded by Title VII of Division N in the Consolidated Appropriations Act, 2023 (Public Law 117-328) to support direct recovery and rebuilding decisions in the wake of declared disasters related to hurricanes and typhoons in 2022. For more information on these efforts, see https://www.usgs.gov/supplemental-appropriations-for-disaster-recovery-activities/typhoon-merbok-coastal-community. Additional information about the field activity from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2024-637-FA Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the dataset in nonproprietary form, this metadata file may include some vendor-specific terminology. 20240710 ground condition at the time source data were collected Complete None planned -162.6202721 -162.5320066 66.9245172 66.8916359 USGS Metadata Identifier USGS:db6b0ba8-c571-4595-81a4-5a5bb16324e0 ISO 19115 Topic Category elevation geoscientificInformation USGS Thesaurus bathymetry Marine Realms Information Bank (MRIB) coast None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC Geographic Names Information System (GNIS) State of Alaska Northwest Arctic Borough City of Kotzebue Kotzebue Sound No access constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. This information is not intended for navigation purposes. PCMSC Science Data Coordinator U.S. Geological Survey, Pacific Coastal and Marine Science Center mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov kotzebue_2024_bathy_browse.png Satellite image overlain with bathymetry data points collected offshore of Kotzebue, Alaska in July 2024. PNG MATLAB Version: 9.8.0.1396136 (R2020a) No formal attribute accuracy tests were conducted. All data fall within expected ranges. Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. The estimated horizontal uncertainty of survey points is 0.05 m. Positions of the work skiff from which the survey was conducted were obtained with a survey-grade global navigation satellite system (GNSS) receiver and a GNSS base station. The GNSS base station was set up on an existing benchmark on land (ID BBDY64) during the bathymetry survey. Base station GNSS RINEX files were uploaded to the National Geodetic Survey Online Positioning User Service (OPUS) to derive the final base station coordinates relative to the North American Datum of 1983 (2011 realization). The resulting solutions were compared to the existing coordinates for the benchmark and found to be within 1 cm of published coordinates. Positioning data from the survey vessels were post-processed using Waypoint Grafnav to apply differential corrections from the GNSS base station. Uncertainty in the horizontal positions due to vessel pitch and roll is unquantified but expected to be low given light winds and small waves (less than 1 foot). The estimated vertical uncertainty of survey points is included in the dataset ("Elevation_Uncertainty_m") and ranges from 0.05 to 0.59 m. These values were calculated by summing in quadrature the uncertainties from GNSS positioning, echosounder measurements, and modeled sound speed in water. Manufacturer-reported uncertainty for differentially corrected Trimble GNSS rover positions is 1.5 cm plus 1 ppm of the survey baseline, combined with the vertical accuracy of the NGS OPUS-derived GNSS base station position. The single-beam echosounder used in this study has a reported vertical accuracy of 1 cm. The speed of sound in water was not measured during this survey, but it was modeled using representative Arctic coastal temperature and salinity ranges; this uncertainty increases with depth. Vertical error due to vessel pitch and roll was not quantified but is expected to be low given light winds and waves less than 1 ft. Pitch and roll under 4.5 degrees do not affect depth readings for the 9-degree beam transducer, assuming a vertical antenna/transducer installation and relatively flat seafloor. For larger pitch/roll values the depth measurement increases only slightly: a pitch/roll of 20 degrees (effective beam tilt of 15.5 degrees) would increase depth readings by only approximately 3.8 percent. Single-beam bathymetry data were collected on July 10, 2024, using a survey-grade echosounder. The system consisted of a CEE HydroSystems CEESCOPE with a 200 kHz transducer (9-degree beam angle) and a Trimble GNSS receiver. The transducer and receiver were attached to the bottom and top (respectively) of a 2.20 meter-long survey rod. The rod was mounted to the side of a 25 ft aluminum work skiff using an adjustable angle bracket. The rod was rotated to a vertical position using a bubble level once the skiff was underway and lowered into the water so the transducer was submerged to a depth of 20 cm. GNSS positions were logged at 10 Hz while traveling at a target speed of under 3 meters per second. Wind conditions were light with 1 ft waves. 20240710 Survey positions were post-processed using a base station and differential post-processing. The position of the GNSS base station was derived from a static GNSS occupation on July 10, 2024. The static observations were processed using the National Geodetic Survey Online Positioning User Service (OPUS) and averaged to derive the final base station coordinates relative to the North American Datum of 1983 (2011 realization). Positioning data from the GNSS receiver on the vessel was post-processed using Waypoint Grafnav to apply differential corrections from the GNSS base station. Orthometric elevations relative to the NAVD88 vertical datum were computed using National Geodetic Survey GEOID12B offsets. Bathymetric soundings were merged with post-processed positioning data and spurious soundings were removed using a custom Graphical User Interface (GUI) programmed with the computer program MATLAB. 20240820 All available bathymetry data from the survey were compiled into a comma-delimited text file for distribution. 20251124 Point Point 184780 Universal Transverse Mercator 3 0.9996 -165.0 0.0 500000.0 0.0 coordinate pair 0.6096 0.6096 meters D NAD 1983 2011 GRS 1980 6378137.0 298.257222101 bathymetry_kotzebue_20240710.csv Comma Separated Value (CSV) file containing data. Producer Defined Longitude Longitude in decimal degrees, WGS 1984 Producer Defined -162.6202721 -162.5320066 decimal degrees 0.0000001 Latitude Latitude in decimal degrees, WGS 1984 Producer Defined 66.8916359 66.9245172 decimal degrees 0.0000001 Easting_m_UTM X coordinate (easting) in meters NAD83(2011) / UTM zone 3N (EPSG: 6332) Producer Defined 604177.02 607978.28 meters 0.01 Northing_m_UTM Y coordinate (northing) in meters NAD83(2011) / UTM zone 3N (EPSG: 6332) Producer Defined 7421341.14 7425060.15 meters 0.01 Elevation_m_NAVD88 Orthometric height (elevation) in meters NAVD88 GEOID12B Producer Defined -17.86 0.84 meters 0.01 Elevation_Uncertainty_m Estimated elevation uncertainty in meters Producer Defined 0.05 0.59 meters 0.01 UTM_Zone UTM Zone in NAD83(2011) / UTM zone 3N (EPSG: 6332) Producer Defined 3N UTM Zone 3 North Producer defined These metadata describe a comma-separated value (csv) file containing nearshore and inland bathymetry data from Kotzebue, Alaska. The first line is a header line and each subsequent line contains x and y coordinates in decimal degrees WGS 84 (EPSG: 4326), x and y coordinates in meters NAD83(2011) / UTM zone 3N (EPSG: 6332), an orthometric height (elevation) in meters NAVD88 GEOID12B, the uncertainty associated with orthometric height, in meters, and the UTM zone used (3N). U.S. Geological Survey U.S. Geological Survey - CMGDS mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov These data are available in a comma-separated value format (csv) accompanied by CSDGM FGDC-compliant metadata. 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 on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. Comma-delimited text Microsoft Excel (version 2408 (Build 17928.20538 Click-to-Run)) comma-delimited text file No compression applied. 10.6 https://doi.org/10.5066/P13YIWKC Data and metadata can be downloaded using the Network_Resource_Name link and scrolling down to the Sonar Data section. None These data can be opened with any text viewer, spreadsheet editor, or geographic information systems (GIS) software. 20260313 PCMSC Science Data Coordinator U.S. Geological Survey, Pacific Coastal and Marine Science Center mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998