Richard M. Buzard Li H. Erikson Ann E. Gibbs Alexander G. Snyder Anita C. Engelstad Cordell Johnson Joshua B. Logan Alexander L. Nereson Daniel J. Nowacki Jin-Si R. Over 20260313 2.0 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 H. 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, CA 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 Elevation point data were collected in Deering, Golovin, Koyuk, Kotzebue, Shishmaref, Teller, and Unalakleet, Alaska between June 2024 and August 2025. Coastal elevation profiles were measured at previously established locations. Other data points are categorized as base station, bathymetry, benchmark, camera calibration data, community-based monitoring profile, drainage observation, flood staff, ground control point, miscellaneous, and water level. The elevation data were collected with real-time kinematic global navigation satellite system (RTK-GNSS) equipment. Data are available in a single CSV file per community. This product was created to help 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 document existing conditions and support the development of dynamic flood models for more than 20 communities along the northwest coast of Alaska. This product is intended for reuse by scientists, managers, and the general public. Additional information about the field activity or activities from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2024-634-FA https://cmgds.marine.usgs.gov/fan_info.php?fan=2024-635-FA https://cmgds.marine.usgs.gov/fan_info.php?fan=2024-637-FA https://cmgds.marine.usgs.gov/fan_info.php?fan=2025-628-FA 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. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20240607 20250813 Ground condition at time data were collected Complete None planned -166.369518 -160.784959 66.904291 63.870529 USGS Metadata Identifier USGS:1299e64a-5ee3-4dfa-ac28-f1eed1b89d3c ISO 19115 Topic Category geoscientificInformation Marine Realms Information Bank (MRIB) keywords beach shore Data Categories for Marine Planning Bathymetry and Elevation USGS Thesaurus coastal processes geomorphology topography geospatial datasets None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC Typhoon Merbok Geographic Names Information System (GNIS) State of Alaska Unalakleet Koyuk Kotzebue Deering Golovin Shishmaref Teller 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. U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

2885 Mission Street

Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov GNSS_ElevationData_locations.png Satellite image showing the locations where elevation data were collected. PNG Trimble Business Center, National Geodetic Survey Online Positioning User Service (https://geodesy.noaa.gov/OPUS/) No formal accuracy assessment was performed. All data fall within expected ranges. Dataset is considered complete for the information presented, as described in the abstract. Horizontal accuracies of the base stations are computed using the National Geodetic Survey Online Positioning User Service. Horizontal errors of remaining points are computed during post-processing. Horizontal errors of all points are listed in the CSVs and do not exceed 0.075 m. Point IDs 11536-11548 and 11755-13492 in the Shishmaref CSV were collected using a GNSS system mounted to a moving vessel near the shoreline. Reported elevations are of the sea surface at the time of collection. Motion from boat maneuvering, waves, and other factors likely increases horizontal position uncertainty by an unknown amount. Vertical accuracies of the base stations are computed using the National Geodetic Survey Online Positioning User Service. Vertical errors of remaining points are computed during post-processing. Vertical errors of all points are listed in the CSVs and do not exceed 0.117 m. Point IDs 11536-11548 and 11755-13492 in the Shishmaref file were collected using a GNSS system mounted to a moving vessel near the shoreline; reported elevations are of the sea surface at the time of collection. Motion from boat maneuvering, waves, and other factors likely increases vertical position uncertainty by an unknown amount. The topographic survey data were acquired using multi-constellation dual-frequency GNSS rovers operating in real-time kinematic (RTK) or post-processed kinematic (PPK) mode. For measuring discreet points (such as ground control points), the GNSS rover was placed on a fixed-height rod and set to occupy the point for the duration of the observation (typically 10 - 30 seconds). For continuous measurements, the rover was either mounted to a backpack (for foot-based surveys), or to a vehicle such as an ATV, and set to record measurements at a fixed interval (typically 1-second). 20250813 All measurements were referenced to a concurrently operating GNSS base station operating on a nearby benchmark. Reference coordinates for the benchmarks were derived using the average of multiple high-quality position solutions from the National Geodetic Survey (NGS) Online Positioning User Service (OPUS). 20250813 Post-processing of PPK rover measurements was conducted using the Trimble Business Center GNSS post-processing software. 20250913 Elevation data collected during USGS field activity 2025-628-FA from Shishmaref and Teller were added to the data release. The previous process steps were revised to provide additional details about data acquisition and processing. 20260211 Alexander L. Nereson U.S. Geological Survey Geologist mailing and physical

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Santa Cruz CA 95060 831-460-7577 anereson@usgs.gov Data were post-processed in the Universal Transverse Mercator (UTM) zones referenced to North American Datum of 1983 with National Adjustment of 2011 (NAD83 [2011]). Eastings and northings are relative to the local UTM zone. Latitude and longitude are in WGS 1984. Elevations reference the North American Vertical Datum of 1988 using corrections from GEOID12B for Alaska (NAVD 88 [GEOID12B]). Point Point 11852 0.000001 0.000001 Decimal degrees WGS_1984 WGS_1984 6378137.0 298.257223563 North American Vertical Datum of 1988 0.001 Meters Explicit elevation coordinate included with horizontal coordinates GNSS_ElevationData_<CommunityName>_YYYYMM.csv Coastal elevation measurements Producer defined Point_ID Unique identifying name Producer defined Automatically generated sequential numbers Easting_m_UTM Easting coordinate. For Golovin, Kotzebue, Shishmaref, and Teller: NAD83(2011)/UTM zone 3N (EPSG: 6332). For Unalakleet and Koyuk NAD83(2011)/UTM zone 4N (EPSG: 6333). Producer defined 397530.834 607283.332 Meters 0.001 Northing_m_UTM Northing coordinate. For Golovin, Kotzebue, Shishmaref, and Teller: NAD83(2011)/UTM zone 3N (EPSG: 6332). For Unalakleet and Koyuk NAD83(2011)/UTM zone 4N (EPSG: 6333). Producer defined 7083816.221 7422775.023 Meters 0.001 UTM_Zone UTM zone in which location is located Producer defined 3N UTM zone 3N (EPSG: 6332) Producer defined 4N UTM zone 4N (EPSG: 6333) Producer defined Elevation_m_NAVD88 Elevation relative to NAVD88 (GEOID12B). A null or no data value of -9999.000 is used for records where elevation was not reliably measured due to undocumented antenna heights above the ground surface. Producer defined 0.358 51.886 Meters 0.001 Latitude Latitude coordinate Producer defined 63.870529 66.904291 Decimal degrees 0.000001 Longitude Longitude coordinate Producer defined -166.369518 -160.784959 Decimal degrees 0.000001 Horizontal_Precision_m Horizontal error Producer defined 0.006 0.075 Meters 0.001 Vertical_Precision_m Vertical error. A null or no data value of -9999.000 is used for records where elevation was not reliably measured due to undocumented antenna heights above the ground surface. Producer defined 0.003 0.117 Meters 0.001 Datetime_UTC Start date and time in UTC (month/day/year hour:minutes) Producer defined 06/07/2024 03:44 08/13/2025 06:05 MM/DD/YYYY hh:mm Notes Description of point Producer defined Descriptive text. Missing information is marked by NAN (not a number) Profile_Line Coastal elevation profile number. Where not applicable, a fill value of -9999 is used Producer defined 1 102 dimensionless Point_Category Descriptive text of the point category Producer defined Base station the location of the GNSS-RTK survey base station Producer defined Benchmark location of recovered benchmark Producer defined Camera calibration data GNSS point taken to support calibration of camera system Producer defined Community based monitoring profile an elevation profile used by the community for erosion monitoring that is not a designated profile in the Alaska Coastal Profile Tool Producer defined Drainage observation GNSS point taken to support understanding of drainage, such as culverts, ditches, and bare earth elevation in dense vegetation Producer defined Flood staff location of a USGS installed flood staff Producer defined Ground control point (GCP) GNSS point taken as a control to support georeferencing Producer defined Miscellaneous GNSS point taken that does not fit into any of these categories or may not be needed Producer defined Profile GNSS point taken along a profile as numbered in the Alaska Coastal Profile Tool Producer defined Water level GNSS point taken at a still water elevation at a specified time Producer defined The first line of the csv file is a header line. 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 csv format 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 CSV contains location and elevation data No compression applied. 1.68 https://doi.org/10.5066/P13YIWKC Data can be downloaded using the Network_Resource_Name link then scrolling down to the Location-Elevation Data section. None. The CSV data can be viewed with any text reading software. 20260313 U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator 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