Daniel J. Nowacki Cordell Johnson Richard M. Buzard Alexander G. Snyder Li Erikson 20250708 tabular digital data 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: 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: U.S. Geological Survey data release, https://doi.org/10.5066/P13YIWKC This dataset contains nearshore bathymetry measurements collected at the entrance to Golovnin Lagoon, Alaska. The data were collected in September 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=2024-635-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. 20240911 ground condition at the time source data were collected Complete None planned -163.08766 -162.99025 64.54394 64.52270 USGS Metadata Identifier USGS:55f62112-931f-464e-a478-e54778230e75 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 Nome Census Area City of Golovin Golovnin Bay Golovnin Lagoon 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 golovnin_lagoon_2024_bathy_browse.png Satellite image overlain with bathymetry data points collected at the entrance to Golovnin Lagoon, Alaska in September 2024. PNG MATLAB Version: 9.8.0.1396136 (R2020a) No formal attribute accuracy tests were conducted. 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. 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. Survey-grade positions of the small boat were achieved with global navigation satellite system (GNSS) receivers and a single GNSS base station. The position of the GNSS base station was derived from two static GNSS occupations from July 10 and 11, 2024, with durations of approximately 11 and 12 hours, respectively. 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 survey vessels were post-processed using Waypoint Grafnav to apply differential corrections from the GNSS base station. Manufacturer reported accuracy for the differentially corrected horizontal positions for the GNSS rover trajectories is 0.8 cm plus 1 ppm. Baselines from the GNSS base station varied between 0.4 km and 2.8 km, suggesting the average horizontal accuracy of survey vessel position to be about 3.6 cm. Uncertainty in the horizontal positions associated with pitch and roll of the survey vessels is unknown. Uncertainty in the final elevations is derived from the combination of uncertainty in the GNSS positioning and bathymetric sounding measurements. Manufacturer reported accuracy for the differentially corrected vertical positions for the GNSS rover trajectories is 1.5 cm plus 1 ppm relative to the benchmark elevation, combined with the vertical accuracy of the NGS OPUS-derived position of the GNSS base station. Baselines from the GNSS base station reached 2.8 km, suggesting the vertical accuracy of survey vessel GNSS height relative to the ellipsoid to be 1.8 cm. However, the Geoid12b error in this region is 0.352 meters, bringing the orthometric (NAVD88) vertical accuracy to 0.354 m. The manufacturer of the single-beam echosounder used in this study reports a vertical accuracy of 1 cm. Additional uncertainty in the final computed elevations data is related to unmeasured variability in the speed of sound used to compute depths from bathymetric soundings and, thus, is depth-dependent. Based on analysis of available speed of sound measurements, we estimate uncertainties in the final depth soundings to be no greater than 1 percent of the water depth. The total vertical uncertainty is calculated using the constant- and depth-dependent factors summed in quadrature. Due to the relatively large error in the Geoid12b model, the final orthometric elevations range from 35.4 cm to 37.7 cm, with an average of 35.6cm. However, when working within geoid 12b, we recommend using the vertical accuracy values relative to the to the ellipsoid, which range from 2.1 cm to 13.1 cm, with an average of 7.6 cm. Uncertainty in the vertical positions associated with pitch and roll of the survey vessels is unknown. Bathymetric data were collected using a single-beam sonar system and global navigation satellite system (GNSS) receiver mounted on a small boat. The sonar systems consisted of a CEE Hydrosystems CeeScope single-beam echosounder and 200 kHz transducer with a 9-degree beam angle. Depths from the echosounders were computed using sound velocity profiles measured using a YSI CastAway CTD during the survey. Positioning of the survey vessels was determined at 10 Hz using survey-grade GNSS receivers. Small boat operator to surveyed lines at speeds of 2 to 3 meters per second. 20240911 Positions of the survey platforms were post-processed using a single-base station and differential post-processing. The position of the GNSS base station was derived from two static GNSS occupations from September 10 and 11, 2024, with durations of approximately 11 and 12 hours, respectively. 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 GEOID12A offsets. Bathymetric data 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. The final point data from the PWCs are projected in Cartesian coordinates using the UTM Zone 3 North, meters coordinate system. 20241020 All available bathymetry data from the survey were compiled into a comma-delimited text file for distribution. 20250625 Point Point 213752 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_golovnin_lagoon_2024.csv Comma Separated Value (CSV) file containing data. Producer Defined Longitude Longitude in decimal degrees, WGS 1984 Producer Defined -163.0859978 -162.9919697 decimal degrees 0.0000001 Latitude Latitude in decimal degrees, WGS 1984 Producer Defined 64.5229975 64.5437963 decimal degrees 0.0000001 Easting_m_UTM X coordinate (easting) in meters NAD83(2011) / UTM zone 3N (EPSG: 6332) Producer Defined 591785.48 596363.12 meters 0.01 Northing_m_UTM Y coordinate (northing) in meters NAD83(2011) / UTM zone 3N (EPSG: 6332) Producer Defined 7156801.94 7158997.85 meters 0.01 UTM_Zone UTM Zone in NAD83(2011) / UTM zone 3N (EPSG: 6332) Producer Defined 3N UTM Zone 3 North Producer defined Elevation_m_NAVD88 Orthometric height (elevation) in meters NAVD88 GEOID12B Producer Defined -13.41 0.25 meters 0.01 These metadata describe a comma-separated value (csv) file containing bathymetry data from the entrance to Golovnin Lagoon, Alaska. The first line is a header line and each subsequent line contains x and y coordinates in meters NAD83(2011) / UTM zone 3N (EPSG: 6332) and an orthometric height (elevation) in meters NAVD88 GEOID12B. 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. 11.3 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. 20250708 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