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    • EnviroAtlas - Hydrologic Sinks for the U.S. Pacific Territories

    Metadata Updated: August 12, 2025

    This EnviroAtlas GIS dataset represents hydrologic sinks and major depressions in the landscape that are more than 2 meters deep, have a surface area of more than 78 square meters, and are fully on land. The dataset covers nine islands in the U.S. Pacific Territories of Guam, the Northern Mariana Islands, and American Samoa (the nine islands are Guam, Saipan, Tinian, Aguijan, Rota, Tutuila, Ofu, Olosega, and Ta'u) and was created using Digital Elevation Models from NOAA (2019-2022) as well as NOAA CCAP 1m landcover (2020-2021) and NCCOS (NOAA National Centers for Coastal and Ocean Science) shoreline files (2004-2005). This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

    Access & Use Information

    License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

    Downloads & Resources

    Dates

    Metadata Date August 11, 2025
    Metadata Created Date August 12, 2025
    Metadata Updated Date August 12, 2025
    Reference Date(s) June 11, 2025 (creation), June 11, 2025 (publication)
    Frequency Of Update asNeeded

    Metadata Source

    Harvested from Environmental Dataset Gateway ISO Geospatial Metadata

    Other Data Resources

    Additional Metadata

    Resource Type Dataset
    Metadata Date August 11, 2025
    Metadata Created Date August 12, 2025
    Metadata Updated Date August 12, 2025
    Reference Date(s) June 11, 2025 (creation), June 11, 2025 (publication)
    Responsible Party U.S. Environmental Protection Agency, Office of Research and Development - Center for Public Health and Environmental Assessment (CPHEA), EnviroAtlas (Publisher)
    Contact Email
    Guid BBE4C3A6-1DE5-48F3-B043-4164830B35EB
    Access Constraints https://edg.epa.gov/EPA_Data_License.html
    Bbox East Long 180
    Bbox North Lat 15.284043
    Bbox South Lat -19.338041
    Bbox West Long -180
    Coupled Resource
    Frequency Of Update asNeeded
    Harvest Object Id afbb0624-08ce-4bd1-876f-ba69e0a5c12e
    Harvest Source Id 9b3cd81e-5515-4bb7-ad3c-5ae44de9b4bd
    Harvest Source Title Environmental Dataset Gateway ISO Geospatial Metadata
    Licence None. Please check sources, scale, accuracy, currency and other available information. Please confirm that you are using the most recent copy of both data and metadata. Acknowledgement of the EPA would be appreciated.
    Lineage 2025-03-14 Following an internal review and comparison of multiple sink mapping outputs using various Digital Elevation Model (DEM) smoothing methods and resolutions (including visual comparison to published maps of sinks and input from WERI (the Water and Environmental Research Institute of the Western Pacific, at the University of Guam)), the project team decided to round DEM values to integers prior to running hydrologic tools. This helped remove minor surface noise and preserve the true shape and extent of sinks. 2025-03-18 Data Selection. DEM data resolution of approximately 3 meters was decided on. NOAA 3m DEMs for Guam, Saipan, Tinian, Aguijan, Rota (from NOAA Sea Level Rise Viewer). Data year: 2019-2020. Metadata: CNMI: coast.noaa.gov/slrdata/DEMs/MP/CNMI_dem_metadata_fy23.xml ; Guam:coast.noaa.gov/slrdata/DEMs/GU/Guam_dem_metadata_fy23.xml ; Spatial Reference: Guam: The DEM is referenced vertically to the Guam Vertical Datum of 2004 (GUVD04) with vertical units of meters and horizontally to the North American Datum of 1983 (NAD83). CNMI: The DEM is referenced vertically to the Northern Marianas Vertical Datum of 2003 (NMVD03) with vertical units of meters and horizontally to the North American Datum of 1983 (NAD83). NOAA NCEI 1/9 arc second DEM for American Samoa (Tutuila, Ofu, Olosega, and Ta’u). NOAA NCEI Continuously Updated Digital Elevation Model (CUDEM) - Ninth Arc-Second Resolution Bathymetric-Topographic Tiles: American Samoa files: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/dem/NCEI_ninth_Topobathy_AmSam_9460/index.html ; Data year: 2022. Spatial Reference: NAD 1983, Vertical datum: ASVD02 (vertical unit: meters). NOAA CCAP 1m landcover data (2020-2021) and NCCOS (NOAA National Centers for Coastal and Ocean Science) shoreline files (2004-2005) were used for each island. 2025-03-19 Reprojected Guam DEM to WGS 1984 UTM Zone 55N. Rounded DEM values to integers. Used Flow Direction and Sink tools in ArcGIS Pro 3.3.1 to map sinks. Created a depth raster by applying the Fill tool in ArcGIS Pro to the unrounded DEM, and then subtracting the original (unrounded) DEM from the filled DEM. Converted sinks to simplified polygons and assigned depth values using Zonal Statistics. Repeated these steps for Saipan, Tinian, Aguijan, Rota, Tutuila, and the Manu'a Islands. The CNMI DEM was reprojected to WGS 1984 UTM Zone 55N. The American Samoa DEMs were reprojected to WGS 1984 UTM Zone 2S. Vertical datums were not changed. 2025-03-24 Following literature review and communication with stakeholders, the team made the decision to exclude sinks with a depth of 2 meters or less or an area of 78 square meters or less, and any sink not fully on land (based on the NCCOS shoreline files). Completed sink filtering based on these parameters for all islands. 2025-03-28 Made the decision to symbolize sinks based on their dominant landcover (water, impervious, or neither water nor impervious). Calculated the percent area of each sink that is water and percent area that is impervious according to NOAA CCAP 1m landcover data. Created a field titled Sink_Dominant_Landcover and assigned values of "Water," "Impervious," and "Neither Water nor Impervious." 2025-04-28 Calculated the volume of each sink by multiplying the depth, width, and length of each cell, and then using Zonal Statistics to sum up the total volume of each sink.
    Metadata Language eng
    Metadata Type geospatial
    Old Spatial {"type": "Polygon", "coordinates": [[[-180.0, -19.338041], [180.0, -19.338041], [180.0, 15.284043], [-180.0, 15.284043], [-180.0, -19.338041]]]}
    Progress completed
    Spatial Data Service Type
    Spatial Reference System 32655
    Spatial Harvester True
    Temporal Extent Begin 2019-01-01T00:00:00
    Temporal Extent End 2022-12-31T00:00:00

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