Andrew W. Stevens Guy R. Gelfenbaum Jonathan A. Warrick Ian M. Miller Heather M. Weiner 20251206 comma-delimited text data release DOI:10.5066/P1BGEMN5 Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey https://doi.org/10.5066/P1BGEMN5 Andrew W. Stevens Guy R. Gelfenbaum Jonathan A. Warrick Ian M. Miller Heather M. Weiner 2025 data release DOI:10.5066/P1BGEMN5 Pacific Coastal and Marine Science Center, Santa Cruz, CA U.S. Geological Survey Suggested Citation: Stevens, A.W., Gelfenbaum, G.R., Warrick, J.A., Miller, I.M., and Weiner, H.M., 2025, Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, July and August 2023: U.S. Geological Survey data release, https://doi.org/10.5066/P1BGEMN5. https://doi.org/10.5066/P1BGEMN5 Digital elevation models (DEMs) of the Elwha River delta were constructed from bathymetric and topographic surveys collected in July and August 2023. Nearshore bathymetry data were acquired using two personal watercraft (PWCs) and a kayak equipped with single-beam echosounders and survey-grade global navigation satellite systems (GNSS) receivers. Topographic data were collected on foot with survey-grade GNSS receivers mounted on backpacks. A total of 1,301,196 individual elevation points were collected between July 30 and August 2, 2023, and used to create DEM surfaces with linear interpolation. A DEM was generated for the entire Elwha River delta with a resolution of 5 m and another DEM that included the river mouth region had a resolution of 1 m. Data were obtained to assess the coastal geomorphic response following the removal of two dams on the Elwha River. These data are intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems or other software to identify topographic and shallow-water bathymetric features. Additional information about the field activities from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2023-645-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 data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology. 20230730 20230802 Ground condition at time data were collected Complete None planned -123.591536 -123.521030 48.159475 48.135093 USGS Metadata Identifier USGS:c266b4af-2d37-40c5-8b98-33f52f5e15ed ISO 19115 Topic Category elevation Data Categories for Marine Planning Bathymetry and Elevation USGS Thesaurus bathymetry bathymetry measurement topography GPS measurement digital elevation models Marine Realms Information Bank (MRIB) keywords single-beam echo sounder topographic mapping Global Positioning System (GPS) observations 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) Clallam County Olympic Peninsula Strait of Juan de Fuca Elwha River 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. These data are marked with a Creative Common CC0 1.0 Universal License. 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. 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 ew23_dem_1m.png image map showing 1-m resolution digital elevation model (DEM) of Elwha River mouth, color-coded to show elevation PNG MATLAB Version 9.8.0.1396136 (R2024a) International Hydrographic Organization (IHO) 2008 No formal attribute accuracy tests were conducted. No formal logical 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. Digital elevation models (DEMs) are created by interpolating between elevation measurements as much as 50 meters apart, for this reason we cannot evaluate the accuracy of each point in a DEM, only the original data from which it is generated. The horizontal accuracy of the individual points was assessed based on the combined uncertainty of GNSS base stations and kinematic (rover) data points. Manufacturer-reported accuracy for the differentially corrected horizontal positions for the Trimble R7, R8 and R10 receivers used to collect the topographic and bathymetric measurements is 0.8 cm + 0.5 ppm. Baselines from the GNSS base station were typically less than 5 km, suggesting a horizontal accuracy of survey-vessel positions to be 0.825 cm relative to the base station. The combined horizontal uncertainty from the base station coordinate solutions and rover trajectories is between 1.5 cm and 7 cm, with a mean horizontal uncertainty of 3 cm. Uncertainty in the horizontal positions associated with pitch and roll of the survey vessels and variable surveyor posture during the backpack surveys is unknown. Digital elevation models (DEMs) are created by interpolating between elevation measurements as much as 50 meters apart, for this reason we cannot evaluate the accuracy of each point in a DEM, only the original data from which it is generated. An estimated vertical accuracy of 5 cm for the topographic GNSS backpack survey platforms was estimated by combining uncertainty in the base station coordinates and the manufacturer reported vertical accuracy of 1.5 cm + 1 ppm for differential corrected kinematic data. Additional uncertainty in the final computed elevations in the bathymetry data is related to unmeasured variability in the speed of sound used to compute depths from bathymetric soundings and, thus, are depth dependent. Based on analysis of all available sound velocity casts, we estimate the uncertainty in the final elevations to be 0.6 percent of water depth. The total vertical uncertainty is calculated using the standard equation sigmat=v(a^2+(b×d)^2), where sigmat is the total vertical uncertainty, a is the uncertainty of the GNSS vertical position, b is the depth-dependent uncertainty factor (0.006), and d is water depth (International Hydrographic Organization, 2008). Maximum water depths surveyed by the personal watercraft are approximately 18 m, yielding a maximum total vertical uncertainty of 12 cm. Andrew W. Stevens Guy R. Gelfenbaum Jonathan A. Warrick Ian M. Miller Heather M. Weiner 2025 comma-delimited text online U.S. Geological Survey, Pacific Coastal and Marine Science Center https://doi.org/10.5066/P1BGEMN5 digital dataset 20230730 20230802 ground condition at time data were collected bathy data Bathymetric and topographic point data available as part of this data release were combined, and then interpolated into a gridded surface Andrew W. Stevens Guy R. Gelfenbaum Jonathan A. Warrick Ian M. Miller Heather M. Weiner 2025 comma-delimited text online U.S. Geological Survey, Pacific Coastal and Marine Science Center https://doi.org/10.5066/P1BGEMN5 digital dataset 20230731 20230802 ground condition at time data were collected topo data Bathymetric and topographic point data available as part of this data release were combined, and then interpolated into a gridded surface Andrew W. Stevens Guy R. Gelfenbaum Jonathan A. Warrick Ian M. Miller Heather M. Weiner 2023 comma-delimited text online U.S. Geological Survey, Pacific Coastal and Marine Science Center https://www.sciencebase.gov/catalog/item/6418cb68d34eb496d1d1d715 digital dataset 20220809 20220811 ground condition at time data were collected older topo data Topography data from 2022 were used in highly vegetated areas where no elevation change was expected to occur. These older data were combined with bathymetric and topographic data collected in 2023 (part of this data release) and interpolated into a gridded surface. Quality control was applied to raw topography and bathymetry data. Comparisons were performed to ensure internal consistency between the survey platforms. Some of the survey area was not accessible due to growth of dense vegetation. In these areas, topographic data collected in 2022 were used to fill gaps in the survey coverage to generate DEMs with similar spatial extents as in previous surveys. DEMs were produced by linear interpolation of all available elevation point data with the computer program MATLAB. Data were exported in ESRI ARC ascii grid format for distribution. bathy data topo data older topo data 20250710 Raster State Plane Coordinate System 1983 4601 47.5 48.73333333333333 -120.8333333333333 47.0 500000.0 0.0 row and column 0.01 0.01 meters North American Datum of 1983 GRS 1980 6378137.0 298.257222101 North American Vertical Datum of 1988 0.01 meters Explicit elevation coordinate included with horizontal coordinates Attribute Table Table containing attribute information associated with the data set Producer defined Elevation Height in meters relative to the NAVD88 vertical datum, computed assuming a static geoid value of -20.11 m which is based on the NGS Geoid09 offset at the location of the GNSS base station. No data values assigned -9999.00. Projected coordinates provided in Washington State Plane North, meters, EPSG 32148. Producer Defined -18.85 5.37 meters U.S. Geological Survey - Coastal and Marine Geoscience Data System Mailing and Physical Address

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Santa Cruz CA 95060 USA 831-427-4747 pcmsc_data@usgs.gov 1-m and 5-m resolution DEM grids are available in Esri ARC/INFO ASCII GRID format (.asc), along with low-resolution browse graphics of each DEM in png format and associated 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. ArcInfo GRID format ArcGIS 10.1 Esri ARC/INFO ASCII GRID Esri ARC ASCII raster containing 1-m resolution digital elevation model of the Elwha River mouth none 14.3 https://doi.org/10.5066/P1BGEMN5 https://doi.org/10.5066/F72N51GC Elevation data may be accessed and downloaded via the Internet by using the first Network_Resource_Name link and scrolling to the Digital Elevation Model (DEM) Data section. The second link points to a landing page for all of the Elwha coastal surveys. ArcInfo GRID format ArcGIS 10.1 Esri ARC/INFO ASCII GRID Esri ASCII raster file containing 5-m resolution digital elevation model of the Elwha River delta none 3.98 https://doi.org/10.5066/P1BGEMN5 https://doi.org/10.5066/F72N51GC Elevation data may be accessed and downloaded via the Internet by using the first Network_Resource_Name link and scrolling to the Digital Elevation Model (DEM) Data section. The second link points to a landing page for all of the Elwha coastal surveys. png MATLAB Version 9.8.0.1396136 (R2024a) PNG Image PNG image showing 1-m resolution digital elevation model of the Elwha River mouth none 1.70 https://doi.org/10.5066/P1BGEMN5 https://doi.org/10.5066/F72N51GC Elevation data may be accessed and downloaded via the Internet by using the first Network_Resource_Name link and scrolling to the Digital Elevation Model (DEM) Data section. The second link points to a landing page for all of the Elwha coastal surveys. png MATLAB Version 9.8.0.1396136 (R2024a) PNG Image PNG image showing 5-m resolution digital elevation model of the Elwha River delta none 0.76 https://doi.org/10.5066/P1BGEMN5 https://doi.org/10.5066/F72N51GC Elevation data may be accessed and downloaded via the Internet by using the first Network_Resource_Name link and scrolling to the Digital Elevation Model (DEM) Data section. The second link points to a landing page for all of the Elwha coastal surveys. None 20251206 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 Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998