Kai A. Parker Kees Nederhoff Li H. Erikson Anita C. Engelstad Maya K. Hayden Patrick L. Barnard Eric E. Grossman 20251126 text, binary, and netcdf data release DOI: 10.5066/P13HYXKY Pacific Coastal and Marine Science Center, CA U.S. Geological Survey https://doi.org/10.5066/P13HYXKY Kai A. Parker Kees Nederhoff Li H. Erikson Anita C. Engelstad Maya K. Hayden Patrick L. Barnard Eric E. Grossman 2025 data release DOI: 10.5066/P13HYXKY Pacific Coastal and Marine Science Center, CA U.S. Geological Survey Suggested Citation: Parker, K., Nederhoff, K., Erikson L.H., Engelstad, A.C., Hayden, M.K., Barnard, P.L., and Grossman, E.E., 2025, CoSMoS-Puget Sound Modeled Flood Hazards at King County - Washington: U.S. Geological Survey data release, https://doi.org/10.5066/P13HYXKY. https://doi.org/10.5066/P13HYXKY The datasets provided here consist of SFINCS model files and sample input files used for Coastal Storm Modeling System (CoSMoS) simulations of flood hazards in King County, Washington. The models produce outputs for a suite of hazard products (see products in this release), such as flood depths, flood extents, and others. In this release, example forcing files for a single water year and a sea level rise of 0.0 m are provided, in addition to all other files needed to run the model. This product was created to fulfill the Bureau-wide vision of an integrated, predictive science capability to support Washington communities in building resiliency from natural disasters, sovereignty and self-determination, and emergency response and planning capacity. These data are intended for policy makers, resource managers, science researchers, technical users, students, and the general public. These data are not intended to be used for navigation. This work is one portion of ongoing national modeling efforts. The Coastal Storm Modeling system (CoSMoS) uses several tiers of numerical models to make detailed predictions (meter-scale) of flooding and erosion over large geographic scales. For more information on CoSMoS implementation, see https://www.usgs.gov/centers/pcmsc/science/coastal-storm-modeling-system-cosmos 2025 publication year Complete None planned -122.583625 -122.025100 47.819405 47.206513 USGS Metadata Identifier USGS:55db94ae-6970-4e52-8445-c1415776a781 Data Categories for Marine Planning Physical Habitats and Geomorphology Global Change Master Directory (GCMD) Hazards Planning Ocean Waves Ocean Winds Beaches Sea Level Rise Storm Surge Extreme Weather Water Depth USGS Thesaurus Climate Change Storms Wind Floods Sea-level Change mathematical modeling effects of climate change earth sciences ISO 19115 Topic Category Oceans ClimatologyMeteorologyAtmosphere Marine Realms Information Bank (MRIB) keywords sea level change waves 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 Washington King County 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 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 This work was funded by the United States Geological Survey (USGS) Coastal and Marine Hazards and Resources Program, King County Department of Natural Resources under Statement of Work 21ZPCOLL210705, and the United States Environmental Protection Agency (EPA) under Statement of Work DW-014-92578201/ EPA-CF-0000007695 to the USGS. The contents of this document do not necessarily reflect the views and policies of the EPA, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Computation resources were supported by the USGS Advanced Research Computing (Falgout and others, 2024). The datasets were created in a Windows 11 Operating system, using python 3.12.9. Deltares 2025 Deltares, 2025, SFINCS online manual documentation, Available online: sfincs.readthedocs.io (accessed 02 March 2025) https://sfincs.readthedocs.io/en/latest/index.html J.T. Falgout J. Gordon B. Williams M.J. Davis 2024 Falgout, J.T., Gordon J., Williams B., Davis M. J., USGS Advanced Research Computing, USGS Denali Supercomputer: U.S. Geological Survey, https://doi.org/10.5066/P9PSW367 https://doi.org/10.5066/P9PSW367 Kees Nederhoff Kai Parker Eric E. Grossman 2025 Nederhoff, K., Parker, K., and Grossman, E., 2025, Beyond the 100-Year Flood: Probabilistic Flood Hazard Assessment for King and Pierce Counties under Future Climate Scenarios: EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-4909. https://doi.org/10.5194/egusphere-2025-4909 Attribute values are model-derived water depths due to plausible sea-level rise and future storm conditions and therefore cannot be validated against observations. The projections were generated using the latest downscaled climate projections from the Coupled Model Intercomparison Project (CMIP6). Data have undergone quality checks and meet standards. Dataset is considered complete for the information presented. Data are concurrent with topobathymetric digital elevation model (DEM) locations. Model-derived data are accurate within published uncertainty bounds, indicative of total uncertainty from elevation data sources and model processes. See Nederhoff and others, 2025 for additional information on vertical accuracy and uncertainty layer development. D.J. Tyler Jeff J. Danielson Eric E. Grossman R.J. Hockenberry 2020 GeoTIFF online U.S. Geological Survey https://doi.org/10.5066/P95N6CIT online database 2020 publication date TBDEM Topobathymetric digital elevation model U.S. Geological Survey 2016 text online U.S. Geological Survey http://dx.doi.org/10.5066/F7P55KJN online database 2016 publication date USGS streamflow USGS streamflow used to correct TBDEM elevations National Oceanic and Atmospheric Administration (NOAA) 2025 online National Oceanic and Atmospheric Administration (NOAA) https://tidesandcurrents.noaa.gov/stationhome.html?id=9447130 https://tidesandcurrents.noaa.gov/ online database 1995 2025 ground condition at time data were collected tide gauge tide gauge data used to calibrate and validate the model Federal Emergency Management Agency (FEMA) 2025 online Federal Emergency Management Agency (FEMA) https://msc.fema.gov/portal/home online database 2020 publication date FEMA FIRM All FEMA Flood Insurance Rate Maps (FIRM) panel tiles in King County, Washington, were used to compare previous modeled water levels with the SFINCS model. D. Eilander R. de Goede T. Leijnse M. van Ormondt K. Nederhoff H. C. Winsemius 2025 online Deltares https://doi.org/10.5281/zenodo.15270197 software 2025 publication date HydroMT-SFINCS model software files Maarten van Ormondt Tim Leijnse Kees Nederhoff Roel de Goede Ap van Dongeren Tycho Bovenschen Koen van Asselt 2024 online Deltares https://doi.org/10.5281/zenodo.13691619 software 2024 publication date SFINCS model software files A SFINCS model was developed for the full extent of King County. Developed files include model domain (sfincs.inp, sfincs.msk, sfincs.dep, sfincs.ind, sfincs.qinf, sfincs_subgrid.nc), settings (sfincs.inp), forcing (sfincs.dis, sfincs.precip, sfincs.src, sfincs_bndbzs.nc), and subgrid structure files (sfincs.weir). See Deltares SFINCS manual (2025) for a full description of each of these model files. The model was set up in a projected coordinate system (Universal Transverse Mercator (UTM) zone 10 N) and elevations are referenced to the North American Vertical Datum of 1988 (NAVD88). Bed level data files (sfincs.dep) and subgrid tables (sfincs_subgrid.nc) were populated by interpolating TBDEM elevations to the cartesian model grid. The model grid was setup with a 50 meter (m) computational grid resolution with 2m subgridding. In regions of unresolved river bathymetry, TBDEM elevations were corrected with a channel depth inverted iteratively from USGS streamflow stage data. Additionally, levees and other blocking features were implemented as subgrid structures (sfincs.weir) to ensure that maximum elevations were accurately represented in the simulations. Model files were developed using HydroMT-SFINCS and SFINCS model 2.2.1. Model setup was calibrated and validated against NOAA tide gauge data, USGS streamflow data, and compared to previous modeled water levels (such as FEMA FIRM maps) and qualitative flood extents from recent events. For a full description of the model setup, see Nederhoff and others, 2025. Simulation were setup as 100 separate year-long simulations, of which one example simulation year is bundled here. TBDEM HydroMT-SFINCS USGS streamflow tide gauge FEMA FIRM SFINCS 20250101 Raster Pixel Universal Transverse Mercator 10 0.9996 -123.0 0.00000 500000.0 0.00 row and column 2 2 Meters NAD83 GRS 1980 6378137.00 298.257222101 North American Vertical Datum of 1988 0.01 meters Implicit coordinate SFINCS example model inputs (SFINCS_ModelInput_King.zip) One zip file with sample time-series forcing data and all necessary input files. Producer defined Model setup files include all files necessary to run SFINCS model simulations. To provide the user with an example, the boundary conditions for a single simulation water year are included here. Please review the rest of the metadata record for additional details and information. 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 as text and binary files contained in a zip file 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. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. text,binary, and netcdf Zip file (SFINCS_ModelInput_King.zip) contains 12 model input files for the SFINCS model WinZip 649.4 https://doi.org/10.5066/P13HYXKY Data can be downloaded using the Network_Resource_Name link then scrolling down to the Simulation Data section. None. text data can be viewed with any text reading software and binaries can be read using SFINCS model tools (such as HydroMT-SFINCS) 20251126 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