Geospatial data in support of structured decision making for George Washington Birthplace National Monument, Virginia

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Frequently anticipated questions:

What does this data set describe?

Title:
Geospatial data in support of structured decision making for George Washington Birthplace National Monument, Virginia
Abstract:
Salt marshes provide a range of ecosystem services, including storm protection, recreation, and commercial fishery habitat provision. The National Park Service (NPS) aims to preserve and protect salt marshes in order to achieve multiple objectives which address their mission: to preserve unimpaired the natural and cultural resources and values of their publicly held lands. Ongoing threats, including sea-level rise, sediment deficits, invasive species, and anthropogenic pressure have led to substantial salt marsh loss in the northeast US over the last century prompting increased investment in their protection and restoration. Here we describe a structured decision making (SDM) framework involving eight NPS units designed to help guide restoration planning and investment, through identification of priority marshes. The framework was developed first through a facilitated workshop with all units, followed by unit-specific workshops where priorities were adjusted to reflect the natural and cultural resources within the unit. The final product is a series of maps depicting performance metrics over a consistent geospatial framework. Integration of these metrics into decision support tools will help guide marsh restoration investments through identification of marsh units and complexes that maximize agency priorities and objectives. This dataset represents the regional and unit-specific metrics generated for George Washington Birthplace National Monument (GEWA).
Supplemental_Information:
All links for cited references and data portals were valid at the time of the work, but support for these web resources may change over time.
  1. How might this data set be cited?
    Ackerman, Kate V., Andrews, Brian D., Ganju, Neil K., and Defne, Zafer, 20251211, Geospatial data in support of structured decision making for George Washington Birthplace National Monument, Virginia: data release DOI:10.5066/P13E2NM2, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Ackerman, Kate V., Andrews, Brian D., Ganju, Neil K., and Defne, Zafer, 2025, Geospatial data in support of structured decision making for northeast coastal parks: data release DOI:10.5066/P13E2NM2, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Ackerman, K.V., Andrews, B.D., Ganju, N.K., and Defne, Z., 2025, Geospatial data in support of structured decision making for northeast coastal parks: U.S. Geological Survey data release, https://doi.org/10.5066/P13E2NM2.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -76.937637
    East_Bounding_Coordinate: -76.887618
    North_Bounding_Coordinate: 38.201634
    South_Bounding_Coordinate: 38.166828
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/685ec631d4be025490e9e708/?name=GEWA_SaltMarsh_Browse.png&allowopen=true (PNG)
    Graphic showing the GEWA salt marshes
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2025
    Currentness_Reference:
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • G-polygon (38)
    2. What coordinate system is used to represent geographic features?
      The map projection used is WGS 1984 Web Mercator Auxiliary Sphere (ESRI Full Name: WGS_1984_Web_Mercator_Auxiliary_Sphere).
      Projection parameters:
      Standard_Parallel: 0.0
      Longitude_of_Central_Meridian: 0.0
      False_Easting: 0.0
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.6096
      Ordinates (y-coordinates) are specified to the nearest 0.6096
      Planar coordinates are specified in Meter
      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.25722.
  7. How does the data set describe geographic features?
    GEWA_SDM_Metrics.shp
    Attribute information associated with marsh units of GEWA salt marsh complex. (Source: U.S. Geological Survey)
    FID
    Internal feature number (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry (Source: Esri) Coordinates defining the feature type.
    FID_CMU
    Sequential unique whole number that represents the identification number for each conceptual marsh unit. This attribute was carried over from the original source, mu_lifespan_CB.shp. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:37
    Units:none
    ATOT_M2
    Total surface area of a marsh unit in square meters. This attribute was carried over from the original source, mu_lifespan_CB.shp. (Source: USGS)
    Range of values
    Minimum:493.891
    Maximum:86151.898
    Units:square meters
    AVEG_M2
    Surface area of vegetated part of a marsh unit in square meters. This attribute was carried over from the original source, mu_lifespan_CB.shp. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:66294.873
    Units:square meters
    GMSL05
    Lifespan for a marsh unit (in years) for global mean sea-level rise of 0.5 m by 2100. Negative lifespan values (other than No Data) indicates the estimated lifespan is depleted and loss is imminent. A value of 10,000 indicates a lifespan equal to or greater than 10,000. A value of -9999 indicates no data. This attribute was carried over from the original source, mu_lifespan_CB.shp. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:10000
    Units:years
    GMSL10
    Lifespan for a marsh unit (in years) for global mean sea-level rise of 1.0 m by 2100. Negative lifespan values (other than No Data) indicates the estimated lifespan is depleted and loss is imminent. A value of 10,000 indicates a lifespan equal to or greater than 10,000. A value of -9999 indicates no data. This attribute was carried over from the original source, mu_lifespan_CB.shp. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:10000
    Units:years
    UVVR
    Ratio of unvegetated surface area to vegetated surface area. Ordinarily, UVVR ranges from zero (completely vegetated) to infinity (completely unvegetated). However, it is assigned the value of -1 when completely unvegetated. Note that there can be very large values of UVVR (indicating that the marsh unit is mostly unvegetated). This attribute was carried over from the original source, mu_lifespan_CB.shp. (Source: USGS)
    Range of values
    Minimum:-1
    Maximum:60.984
    Units:none
    Zstar
    Mean wetland elevation above mean sea level relative to the tidal range of the marsh unit. A value of -9999 indicates no data. (Source: USGS)
    Range of values
    Minimum:-0.342
    Maximum:5.998
    Units:unitless
    AMIG_M2
    Potential marsh migration area in square meters. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:90180.777
    Units:square meters
    NWIclass
    Number of NWI subclasses in a marsh unit. (Source: USGS)
    Range of values
    Minimum:1
    Maximum:1
    Units:None
    Ditchkmkm2
    Ditching intensity (linear kilometers of ditch per square kilometer of marsh unit area). (Source: USGS)
    Range of values
    Minimum:0
    Maximum:0
    Units:kilometers per square kilometer
    Phrag
    Presence (1) or absence (0) of Phragmites in a marsh unit. (Source: USGS)
    ValueDefinition
    1Presence of Phragmites in marsh unit.
    0Absence of Phragmites in marsh unit.
    SALS_P
    Presence (1) or absence (0) of priority Saltmarsh Sparrow (SALS) habitat within a marsh unit. (Source: USGS)
    ValueDefinition
    1Presence of priority Saltmarsh Sparrow (SALS) habitat within a marsh unit.
    0Absence of priority Saltmarsh Sparrow (SALS) habitat within a marsh unit.
    SAV
    Presence (1) or absence (0) of submerged aquatic vegetation (SAV) within 100m of a marsh unit. (Source: USGS)
    ValueDefinition
    1Presence of SAV within 100m of a marsh unit.
    0Absence of SAV within 100m of a marsh unit.
    BioDiv
    The sum of attributes SALS_P and SAV to indicate whether a marsh unit has priority Saltmarsh Sparrow habitat within the marsh unit, or SAV adjacent to the marsh unit. If both salt marsh sparrow habitat and SAV are present, the value is 2; if only one is present, the value is 1; if neither are present, the value is 0. (Source: USGS)
    ValueDefinition
    2Presence of priority SALS habitat within the marsh unit, and SAV adjacent to the marsh unit.
    1Presence of priority SALS habitat within the marsh unit, or SAV adjacent to the marsh unit.
    0Absence of priority SALS habitat within the marsh unit, nor SAV adjacent to the marsh unit.
    Quantl
    The quantile bin that a marsh unit is assigned to based on its area. The marsh units with the smallest areas are in quantile 1, and the largest marsh units are in quantile 5. (Source: USGS)
    Range of values
    Minimum:1
    Maximum:5
    Units:None
    AssetScore
    An estimate of the protection a marsh unit provides to an asset (building). The asset score ranges from 0 (minimal protection provided by marsh unit) to 10 (maximal protection). (Source: USGS)
    Range of values
    Minimum:0
    Maximum:9
    Units:None
    VegMU_MgC
    Total biomass carbon in the vegetated portion of the marsh unit. A value of -9999 indicates no data. (Source: USGS)
    Range of values
    Minimum:0.703
    Maximum:73.743
    Units:megagrams carbon
    Pop
    The total population within 50 miles of the park boundary. This value is the same for all marsh units. (Source: USGS)
    ValueDefinition
    4,163,669Total population within 50 miles of the park boundary.
    Edu_Val
    Educational values of marsh units. Marsh units that are within 200 m of the vistor center, Memorial House, walking trails, footbridges and picnic areas have educational value (1), others are classified as having no educational value (0). (Source: USGS)
    ValueDefinition
    1Marsh unit has educational value.
    0Marsh unit is not close enough to vistor center, Memorial House, walking trails, footbridges and picnic areas to have educational value.
    Rec_Val
    Recreational value of marsh units. Marsh units that are within 200 m of walking trails, picnic area, kayak launch, and fishing areas have recreational value (1), others are classified as having no recreational value (0). (Source: USGS)
    ValueDefinition
    1Marsh unit has recreational value.
    0Marsh unit does not have recreational value.
    Visit
    The total number of visitors to GEWA in 2023. This value is the same for all marsh units. (Source: USGS)
    ValueDefinition
    98,846Total number of visitors to GEWA in 2023.
    Insp_Val
    Inspirational or aesthetic value of a marsh unit. Marsh units that are within 100 m of the visitor center, Memorial House, walking trails, roads, footbridges, Longwood area, Bridges Creek marsh have inspirational or aesthetic value (1), others are classified as having no inspirational or aesthetic value (0). (Source: USGS)
    ValueDefinition
    1Marsh unit has inspirational or aesthetic value.
    0Marsh unit does not have inspirational or aesthetic value.
    NHS
    Marsh units that are within 1 km of a National Historic Site (NHS, NRHP) have a value of 1, otherwise they have a value of 0. (Source: USGS)
    ValueDefinition
    1Marsh unit is within 1 km of a National Historic Site.
    0Marsh unit is not within 1 km of a National Historic Site.
    CL
    Marsh units that are within 1 km of a Cultural Landscape have a value of 1, otherwise they have a value of 0. (Source: USGS)
    ValueDefinition
    1Marsh unit is within 1 km of a Cultural Landscape.
    0Marsh unit is not within 1 km of a Cultural Landscape.
    NHS_CL
    Marsh unit that are within 1 km of either an NHS or CL site or both have a value of 1 or 2, respectively, otherwise they have a value of 0. (Source: USGS)
    ValueDefinition
    2Marsh unit is within 1 km of a NHS and a CL site.
    1Marsh unit is within 1 km of a NHS or a CL site.
    0Marsh unit is not within 1 km of a NHS nor a CL site.
    Arch
    Marsh unit that are within 100 m of an area of archeological concern have a value of 1, otherwise they have a value of 0. (Source: USGS)
    ValueDefinition
    1Marsh unit is within 100 m of an area of archeological concern.
    0Marsh unit is not within 100 m of an area of archeological concern.
    FLG
    Marsh unit flag indicating anomalous marsh units based on absence of vegetation, elevation, surface area and tidal range extrapolation. FLG values indicate: (-1) no vegetated area in the marsh unit; (-10) marsh unit elevation higher than the 99.8 percentile; (-100) marsh unit elevation less than the 0.2 percentile; (-200) greater than 25 percent of the marsh unit elevation is hydro-flattened; (-1000) marsh unit surface area less than 900 m2; (-10000) mean tidal range of marsh unit is extrapolated; and (0) no flag. Combination of negative values indicates a combination of flags. For example, -1001 indicates no vegetated area and area less than 900 m2.This attribute was carried over from the original source, mu_lifespan_CB.shp. (Source: USGS)
    Range of values
    Minimum:-10200
    Maximum:0
    Units:None
    InOutPark
    Classification of marsh unit as either inside or outside of the park boundary. (Source: USGS)
    ValueDefinition
    inMarsh unit that is inside the park boundary.
    outMarsh unit that is outside the park boundary.
    Entity_and_Attribute_Overview:
    In this dataset, metrics are calculated for marsh units of George Washington Birthplace National Monument (GEWA) to be used in an SDM framework to prioritize management actions. All attributes, as well as attribute definitions, are included even if they are not present in any of the marsh units in the park. This is to ensure consistency across parks and recognition that the attribute is not present rather than unaccounted for.
    Entity_and_Attribute_Detail_Citation: USGS

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Kate V. Ackerman
    • Brian D. Andrews
    • Neil K. Ganju
    • Zafer Defne
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Kate V. Ackerman
    Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2331 (voice)
    508-457-2310 (FAX)
    kackerman@usgs.gov

Why was the data set created?

This shapefile provides the geospatial metrics generated for George Washington Birthplace National Monument (GEWA) to be used in the structured decision making (SDM) process.

How was the data set created?

  1. From what previous works were the data drawn?
    mu_lifespan_CB.shp (source 1 of 24)
    Defne, Z., Ganju, N.K., and Ackerman, K.V., 2023, Lifespan of Chesapeake Bay salt marsh units: data release DOI:10.5066/P9FSPWSF, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    This shapefile is used as a starting point for the SDM metrics shapefile published here (GEWA_SDM_Metrics.shp). The marsh unit unique identification number (FID_CMU), the total area of the marsh unit (ATOT_M2), the area of the vegetated portion of the marsh unit (AVEG_M2), the lifespan under global mean sea-level rise of 0.5m and 1.0m by 2100 (GMSL05, GMSL10), the unvegetated to vegetated marsh ratio (UVVR), and flagged anomalous units (FLG) are all carried from the source shapefile (mu_lifespan_CB.shp) into the GEWA_SDM_Metrics.shp shapefile. Downloaded in April 2024.
    relative_tidal_elevation.tif (source 2 of 24)
    Holmquist, J.R., and Windham-Myers, L., 2021, Relative Tidal Marsh Elevation Maps with Uncertainty for Conterminous USA, 2010: ORNL DAAC, Oak Ridge, TN.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Used the relative tidal elevation (elevation normalized to the tidal range), termed Zstar (Z*). Z* = (orthometric elevation (m) - mean sea level (m)) / (mean high water (m) - mean sea level(m)). Downloaded in April 2024.
    mu_migration_CB.shp (source 3 of 24)
    Defne, Z., Ackerman, K.V., Andrews, B.D., and Ganju, N.K., 2025, Metrics for marsh migration under sea-level rise in Chesapeake Bay: data release DOI:10.5066/P18BWN2U, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Marsh migration potential values for Chesapeake Bay marsh units. Downloaded in March 2025.
    NWI.shp (source 4 of 24)
    U.S. Fish and Wildlife Service, 2020, National Wetlands Inventory: U.S. Fish and Wildlife Service, Washington, D.C..

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution: Downloaded the wetlands data for Virginia in January 2020.
    NortheastUSDitches_Polyline.shp (source 5 of 24)
    Peck, E.K., Walker, J.E., Woodruff, J.D., and Ganju, N.K., 2024, Linear Ditches of Northeastern U.S. Coastal Marshes from Maine to Virginia Derived from 2023 2D Aerial Imagery Basemap: data release DOI:10.5066/P13WF8ZT, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution: Ditches shapefile. Downloaded in March 2024.
    ChemicalComponentPy (source 6 of 24)
    NPS Invasive Plant Management Team, 2024, ChemicalComponentPy.

    Type_of_Source_Media: digital
    Source_Contribution:
    Shapefile of location of Phragmites in GEWA. At the time of publication, Phragmites data were not publicly available from NPS. Received the data from Nate Wender, November 2024.
    SAV.shp (source 7 of 24)
    Virginia Institute of Marine Science, 20231213, Submerged Aquatic Vegetation (SAV) Beds 2022: Virginia Institute of Marine Science, Gloucester Point, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Shapefile of the location of SAV beds. Downloaded in February 2024.
    ACJV_SALS_Priority_Marshes (source 8 of 24)
    Luke, K., 20241006, FWS Saltmarsh Restoration Priorities for the Saltmarsh Sparrow- Atlantic Coast Joint Venture (ACJV): U.S. Fish and Wildlife Service, Panama City, FL.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Salt marshes that are characterized as "priority" marshes are used in this analysis. Downloaded in October 2024.
    GEWA_Base_Data (source 9 of 24)
    Service, National Park, 2021, Base Data, George Washington Birthplace.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Dataset of the GEWA buildings, roads and trails. Data were accessed as a web feature service and exported to a feature class. Accessed January 2025.
    USGS_CCL_MaximumCCL_2022.tif (source 10 of 24)
    Sterne, T.K., Pendleton, E.A., Lentz, E.E., and Henderson, R.E., 2023, Coastal Change Likelihood in the U.S. Northeast Region: Maine to Virginia- Maximum Change Likelihood: data release DOI:10.5066/P96A2Q5X, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Dataset that estimates the coastal change likelihood across the Northeast. Downloaded in March 2024.
    CMU_CB (source 11 of 24)
    Ackerman, K.V., Defne, Z., and Ganju, N.K., 2022, Conceptual marsh units of Chesapeake Bay salt marshes: data release DOI:10.5066/P997EJYB, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Conceptual marsh units that have vegetated and unvegetated polygons delineated. Downloaded in April 2024.
    BiomassC_CONUSTidalMarshes_gCm2.tif (source 12 of 24)
    Woltz, V.L., Stagg, C. LaFosse, Byrd, K.B., Windham-Myers, L., Rovai, A.S., and Zhu, Z., 2023, Biomass Carbon Stock and Net Primary Productivity in Tidal Herbaceous Wetlands of the Conterminous United States: data release DOI:10.5066/P9I1PCLS, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Dataset of the biomass carbon stock in coastal herbaceous wetlands. The first link is to the data release and the second link is to the specific dataset used. Downloaded in March 2024.
    Census_Blocks.shp (source 13 of 24)
    U.S. Department of Commerce, U.S. Census Bureau, Geography Division, Geospatial Products Branch, 2023, TIGER/Line Shapefile, 2020 Census Block: U.S. Census Bureau, Washington, D.C..

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution: Census blocks. Downloaded in March 2024.
    KayakLaunch.shp (source 14 of 24)
    U.S. Geological Survey/National Park Service, 2024, GEWA Kayak Launch.

    Type_of_Source_Media: digital
    Source_Contribution:
    Digitized the location of the kayak launch site at Potomac River Beach, using https://www.nps.gov/gewa/planyourvisit/maps.htm and aerial imagery (Esri World Imagery) for reference. At the time of publication, these data were not digitally available from the National Park Service.
    FishingArea.shp (source 15 of 24)
    Type_of_Source_Media: online
    Source_Contribution: Location of fishing areas. Accessed data August 2024.
    Annual_Visitation (source 16 of 24)
    Service, National Park, 2024, Annual Park Recreation Visits (1967-Last Calendar Year): National Park Service, Washington, D.C..

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution: Number of visitors to GEWA in 2023. Downloaded in August 2024.
    AestheticAreas.shp (source 17 of 24)
    U.S. Geological Survey, 2024, Aesthetic areas.

    Type_of_Source_Media: digital
    Source_Contribution:
    Location of the Longwood area and Bridges Creek marsh area, hand digitized using aerial imagery (Esri World Imagery) as a guide, September 2024.
    Cultural_1.shp (source 18 of 24)
    National Park Service, Cultural Resource GIS Facility, 20220125, Cultural Resource District Polygon: National Park Service, Washington, DC.

    Type_of_Source_Media: online
    Source_Contribution:
    This dataset was accessed and used by Dennis Skidds (NPS) to identify marsh units that are within 1 kilometer (km) of National Historic Sites and Cultural Landscapes.
    Cultural_2.shp (source 19 of 24)
    National Park Service, Cultural Resource GIS Facility, 20220125, Cultural Resource Object Polygon: National Park Service, Washington, DC.

    Type_of_Source_Media: online
    Source_Contribution:
    This dataset was accessed and used by Dennis Skidds (NPS) to identify marsh units that are within 1 km of National Historic Sites and Cultural Landscapes.
    Cultural_3.shp (source 20 of 24)
    National Park Service, Cultural Resource GIS Facility, 20220125, Cultural Resource Site Polygon: National Park Service, Washington, DC.

    Type_of_Source_Media: online
    Source_Contribution:
    This dataset was accessed and used by Dennis Skidds (NPS) to identify marsh units that are within 1 km of National Historic Sites and Cultural Landscapes.
    Cultural_4.shp (source 21 of 24)
    National Park Service, Cultural Resource GIS Facility, 20220125, Cultural Resource Site Point: National Park Service, Washington, DC.

    Type_of_Source_Media: online
    Source_Contribution:
    This dataset was accessed and used by Dennis Skidds (NPS) to identify marsh units that are within 1 km of National Historic Sites and Cultural Landscapes.
    Cultural_5.shp (source 22 of 24)
    National Park Service, Cultural Resource GIS Facility, 20220125, Cultural Resource Site Line: National Park Service, Washington, DC.

    Type_of_Source_Media: online
    Source_Contribution:
    This dataset was accessed and used by Dennis Skidds (NPS) to identify marsh units that are within 1 km of National Historic Sites and Cultural Landscapes.
    GEWA_Arch_Concern.shp (source 23 of 24)
    Birthplace, George Washington, 2024, Area of archeological concern.

    Type_of_Source_Media: digital
    Source_Contribution:
    At the time of publication, areas of archeological concern were not publicly available from National Park Service (NPS). Received the data from GEWA, January 2025.
    NPS_boundary.shp (source 24 of 24)
    Service, National Park, 2022, NPS Unit Boundary-derived Areas of Analysis, Fall 2021: NPS Natural Resources Inventory and Monitoring Division, Washington, DC.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Used for delineation of park boundaries. Downloaded data in July 2022.
  2. How were the data generated, processed, and modified?
    Date: 2025 (process 1 of 20)
    All process steps were performed by either Kate Ackerman or Brian Andrews (contact information in this process step and the next), using ArcGIS Pro (ver.3.2.1). For simple operations the name of the geoprocessing tool used is given in capital letters; for complex operations, the name of the geoprocessing tool used is given in capital letters and any critical parameters used are given in parentheses, separated by a semicolon, immediately after the tool name. The input and output file names are provided in [square brackets] when necessary. Units for length and area calculations are meters (m) and square meters (m2) unless otherwise stated. Person who carried out this activity:
    Kate Ackerman
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    US

    508-548-8700 x2331 (voice)
    508-457-2310 (FAX)
    kackerman@usgs.gov
    Date: 2025 (process 2 of 20)
    Export [mu_lifespan_CB.shp] to create a new shapefile [GEWA_SDM_Metrics.shp], keeping the marsh units that are within and adjacent to the park boundary, and the fields that are needed for the SDM performance metrics: the marsh unit unique identification number (FID_CMU), the total area of the marsh unit (ATOT_M2), the area of the vegetated portion of the marsh unit (AVEG_M2), the lifespan under global mean sea-level rise of 0.5m and 1.0m by 2100 (GMSL05, GMSL10), the unvegetated to vegetated marsh ratio (UVVR), and the flag denoting anomalous marsh units (FLG). Project the shapefile from WGS 1984 Web Mercator Auxiliary Sphere to NAD 1983 (2011) UTM 18N. Person who carried out this activity:
    Brian Andrews
    U.S. Geological Survey
    Geographer
    384 Woods Hole Road
    Woods Hole, MA
    US

    508-548-8700 x2348 (voice)
    508-457-2310 (FAX)
    bandrews@usgs.gov
    Data sources used in this process:
    • mu_lifespan_CB.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 3 of 20)
    Create attribute "Zstar" to calculate elevation relative to tidal range. Calculate the mean relative wetland elevation value relative to tidal range (Zstar (Z*)) within each marsh unit (FID_CMU). Zstar, the relative tidal elevation value, is a metric that normalizes elevation to the tidal amplitude at mean high water. Z* = (orthometric elevation - mean sea level) / (mean high water - mean sea level).
    Run ZONAL STATISTICS AS TABLE (feature zone data: [GEWA_SDM_Metrics.shp], zone field: FID_CMU, value raster: [relative_tidal_elevation.tif], statistics type= Mean) to calculate the average Z* value for each marsh unit. In [GEWA_SDM_Metrics.shp], add new attribute "Zstar" (Double) to attribute table and populate with results of zonal statistics (MEAN) by joining via the "FID_CMU" field. Assign a value of -9999 for marsh units that do not have Zstar data. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • relative_tidal_elevation.tif
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 4 of 20)
    Create attribute “AMIG_M2” to assess the marsh migration potential of each marsh unit, calculated in terms of available migration area, under 2 feet of local sea-level rise, for each marsh unit.
    JOIN "AMIG_M2" from [mu_migration_CB.shp] to [GEWA_SDM_Metrics.shp]. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • mu_migration_CB.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 5 of 20)
    Create attribute “NWIclass” to calculate the number of different coastal wetland (NWI subclasses) types found within a marsh unit.
    (1) Create a shapefile of the NWI classes that are used for the marsh unit analysis. From [NWI.shp] SELECT (ATTRIBUTE LIKE 'E2%EM%' OR ATTRIBUTE LIKE 'E2AB3%' OR ATTRIBUTE LIKE 'E2EM%' OR ATTRIBUTE LIKE 'E2SS%' OR ATTRIBUTE LIKE 'E2US4%'), EXPORT features to create [NWI_exclusive_select.shp]. Add an additional field that captures the first 5 digits of the NWI attribute field (no modifiers are retained).
    (2) PAIRWISE INTERSECT the NWI [NWI_exclusive_select.shp] and the marsh units [GEWA_SDM_Metrics.shp] to assign NWI classes to each marsh unit. DISSOLVE the resulting shapefile (Dissolve field: FID_CMU, Concatenate) to obtain a list of all NWI classes found in each marsh unit. Calculate the number of different NWI subclasses found in each marsh unit. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • NWI.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 6 of 20)
    Create attribute "Ditchkmkm2" to calculate the density of ditches for each marsh unit. It is calculated by summing the linear length of ditches (km) divided by the area of each marsh unit (square kilometers). The final value for each marsh unit is ditching intensity (linear kilometers of ditch per square kilometer of marsh unit area).
    PAIRWISE INTERSECT the ditches [NortheastUSDitches_Polyline.shp] and marsh units [GEWA_SDM_Metrics.shp] then SUMMARIZE ATTRIBUTES by FID_CMU to get total length of ditches in each marsh unit. Calculate the ditch density (km/km2): total length of ditches (km) in a marsh, divided by the total marsh unit area (km2). Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • NortheastUSDitches_Polyline.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 7 of 20)
    Create attribute "Phrag" that indicates the presence or absence of Phragmites in the marsh unit.
    SELECT BY LOCATION (intersect) [ChemicalComponentPy] and [GEWA_SDM_Metrics.shp] to identify marsh units that have Phragmites. If a marsh unit has Phragmites, assign a value of 1 to the marsh unit for the “Phrag” attribute. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • ChemicalComponentPy
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 8 of 20)
    Create attribute "BioDiv" that provides information on the biodiversity of the marsh unit, which is the summation of the "SALS_P" (whether the marsh unit intersects a “priority marsh” for Saltmarsh Sparrow) and the "SAV" (whether the marsh unit is within 100m of seagrass beds) attributes.
    SALS_P: SELECT BY LOCATION (intersect) [ACJV_SALS_Priority_Marshes] and [GEWA_SDM_Metrics.shp] to identify marsh units that intersect priority habitat for Saltmarsh Sparrow. If they intersect, the marsh unit is assigned a value of 1 for the “SALS_P” attribute.
    SAV: SELECT BY LOCATION (intersect, 100 m) [SAV.shp] and [GEWA_SDM_Metrics.shp] to identify marsh units that have seagrass within 100 m of the marsh unit. If seagrass beds are within 100 m of the marsh unit, the marsh unit is assigned a value of 1 for the “SAV” attribute.
    BioDiv: The “BioDiv” attribute is the sum of the “SALS_P” and “SAV” attributes. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • ACJV_SALS_Priority_Marshes
    • SAV.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 9 of 20)
    Create attribute “Quantl” to compare the size of marsh units across the Park. Based on the total marsh unit area, the marsh units are binned into 5 equal area bins. Each marsh unit is placed into a bin based on its size (bin 1 contains the smallest marsh units; bin 5 contains the largest marsh units).
    Calculate the total area of all marsh units, sort marsh units by size, divide the dataset into five approximately equal parts based on area. The smallest marsh units will have a Quantl value of 1, the largest marsh units will have a Quantl value of 5. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 10 of 20)
    Create attribute "AssetScore" to estimate the protection a marsh unit provides to an asset (building). The Asset Score is calculated by dividing the maximum Coastal Change Likelihood (USGS_CCL_MaximumCCL_2022.tif) score within 100 m of an asset by the distance in meters (binned) from the asset to the marsh unit. The Asset Score ranges from 0 (minimal protection provided by marsh unit) to 10 (maximal protection).
    1)PROJECT source shapefiles from WGS 1984 Web Mercator coordinate system to NAD 83 (2011) UTM 18N and output as feature classes within a geodatabase to ensure distance calculations are accurate. Source files: marsh units: [GEWA_SDM_Metrics]; buildings: select relevant buildings from [GEWA_Base_Data]; output: [GEWA_BuildingFeatures_UTM18].
    2)Calculate the maximum CCL value within 100 m of each of the assets (buildings) within GEWA boundary. BUFFER [GEWA_BuildingFeatures_UTM18] by 100 m, output= [GEWA_BID100mBuff]. ZONAL STATISTICS AS TABLE (Input: [GEWA_BID100mBuff]; zone field=BID; Input Value Raster: [USGS_CCL_2022.tif]; Output table: [GEWA_BuildingMaxCCL_100m]; Statistics Type=Maximum).
    3)Calculate the distance in meters from the buildings [GEWABuildingFeatures_UTM18] to the closest point along the boundary of all marsh units [GEWA_SDM_Metrics] that are within 1 km of each feature in [GEWABuildingFeatures_UTM18]. GENERATE NEAR TABLE (Output table: [GEWA_BuildingsNearMU_1km]). Only need to retain the fields "IN_FID", "NEAR_FID", and "NEAR_DIST" from the output table.
    4)Join (JOIN FIELD) the MAX CCL value from table [GEWA_BuildingMaxCCL_100m] (join field=BID) to the output table [GEWA_BuildingsNearMU_1km] (join field=IN_FID; Transfer Fields=MAX).
    5)ADD FIELDS (multiple) (Input Table: [GEWA_SDM_Metrics]; Field Names: "Dist" (Short) and "AssetScore" (Double)).
    6)ADD JOIN (Join one to many) (Input Table: [GEWA_SDM_Metrics]; input field=OBJECTID; Join Table: [GEWA_BuildingsNearMU_1km]; Join Field: NEAR_FID; transfer all fields). EXPORT joined feature class to [GEWA_SDM_Metrics_AS].
    7) Calculate the "AssetScore" field in 2 steps. In [GEWA_SDM_Metrics_AS], first CALCULATE FIELD "Dist" by rounding up the "NEAR_DIST" value (Data type=double from step 3 and 6) in meters to the nearest 100, then dividing the rounded number by 100. For example, a "NEAR_DIST" value of 23.55 m rounds to 100, then divided by 100 gives a “Dist” value of 1; a "NEAR_DIST" of 176.16 m gives "Dist" value of 2. Second, CALCULATE FIELD "AssetScore" by dividing "MAX" (max CCL) by "DIST."
    8)Run PAIRWISE DISSOLVE (input file: [GEWA_SDM_Metrics_AS]; Dissolve field: FID_CMU; Statistics field: AssetScore; Statistics Type: Maximum; Output: [GEWA_SDM_Metrics_AS_Dissolve]) to dissolve duplicate "FID CMU" records from the one-to-many join in step 6. This final step retains the maximum "AssetScore" for any one-to-many relationships between each marsh unit and building pair(s). The output dissolved feature class does not retain all the fields from the source [GEWA_SDM_Metrics_AS] and only retains "FID_CMU" and "MAX_AssetScore."
    9)JOIN FIELD "MAX_AssetScore" from [GEWA_SDM_Metrics_AS] back into original source [GEWA_SDM_Metrics.shp] using the "FID_CMU" field. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • GEWA_Base_Data
    • USGS_CCL_MaximumCCL_2022.tif
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 11 of 20)
    Create attribute “VegMU_MgC” to summarize the amount of biomass carbon in the vegetated part of the marsh unit.
    Extract the vegetated portion of the marsh unit polygons. SELECT BY ATTRIBUTES from [CMU_CB] that are within and adjacent to the park boundary [NPS_boundary.shp] where "TYP"= 'vegetated'; output: [CMU_GEWA_VEG.shp]. PROJECT [CMU_GEWA_VEG.shp] to Albers_Conical_Equal_Area to match the projection of the biomass carbon file.
    Run ZONAL STATISTICS AS TABLE (feature zone data: [CMU_GEWA_VEG.shp], zone field: FID_CMU, value raster: [BiomassC_CONUSTidalMarshes_gCm2.tif], Statistics type=Mean) to get the average biomass carbon for the vegetated portion of the marsh unit. JOIN the MEAN value to [CMU_GEWA_VEG.shp]. Multiply MEAN by the vegetated area of the marsh unit to get total grams of carbon in the vegetated portion of the marsh unit. Report the value in megagrams of carbon (MgC). Assign a value of -9999 for marsh units that do not have carbon data. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • CMU_CB
    • NPS_boundary.shp
    • BiomassC_CONUSTidalMarshes_gCm2.tif
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 12 of 20)
    Create new attribute “Pop” to calculate the total population within 50 miles of the marsh units. The population value is the same for all marsh units.
    SELECT BY LOCATION (intersect, 50 miles) [Census_Blocks.shp] and [GEWA_SDM_Metrics.shp]. Calculate total population in the selected census blocks. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • Census_Blocks.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 13 of 20)
    Create attribute “Edu_Val” that identifies marsh units that are of natural and cultural history educational value to the park. For GEWA, marsh units within 200 m of interpretive points, walking trails, footbridges, and picnic areas are identified.
    From [GEWA_Base_Data] select Visitor's Center, Memorial House, pedestrian roads (walking trails), footbridges and picnic parking area. SELECT BY LOCATION (intersect, 200m) [GEWA_Base_Data] and [GEWA_SDM_Metrics.shp] to identify marsh units that are within 200 m of interpretive points, walking trails, footbridges, and picnic areas. If the features are within 200 m of the marsh unit, the marsh unit is assigned a value of 1. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • GEWA_Base_Data
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 14 of 20)
    Create attribute “Rec_Val” that identifies marsh units that are of recreational value to the park. For GEWA, marsh units within 200 m of walking trails, picnic area, kayak launch, and fishing areas are identified.
    From [GEWA_Base_Data] select pedestrian roads (walking trails) and picnic parking area. SELECT BY LOCATION (intersect, 200m) [GEWA_Base_Data], [KayakLaunch.shp], [FishingArea.shp] and [GEWA_SDM_Metrics.shp] to identify marsh units that are within 200 m of these features. If the features are within 200 m of the marsh unit, the marsh unit is assigned a value of 1. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • GEWA_Base_Data
    • KayakLaunch.shp
    • FishingArea.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 15 of 20)
    Create new attribute “Visit” that is the total number of visitors to the park in 2023. This value is the same for all marsh units.
    The number of visitors to GEWA in 2023 was obtained from [Annual_Visitation]. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • Annual_Visitation
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 16 of 20)
    Create attribute "Insp_Val" that identifies marsh units that are of aesthetic or inspirational value to the park. For GEWA, marsh units within 100 m of the Visitor Center, Memorial House, walking trails, roads, footbridges, Longwood area, and Bridges Creek marsh are identified.
    From [GEWA_Base_Data] select Visitor Center, Memorial House, pedestrian roads (walking trails), roads and picnic parking area. SELECT BY LOCATION (intersect, 100m) [GEWA_Base_Data], [AestheticAreas.shp], and [GEWA_SDM_Metrics.shp] to identify marsh units that are within 100 m of these features.
    If the features are within the specified distance of the marsh unit, the marsh unit is assigned a value of 1. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • GEWA_Base_Data
    • AestheticAreas
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2024 (process 17 of 20)
    Create 3 attributes “NHS,” “CL,” and “NHS_CL” to identify marshes that are close to cultural and historical resources. "NHS" identifies marsh units that are within 1 km of a historic site (National Historic Site (NHS), National Register of Historic Places (NRHP)), "CL" identifies marsh units that are within 1 km of a Cultural Landscape (CL). The attribute "NHS_CL" indicates marsh unit that are within 1 km of either an NHS or CL site or both (value of 1 or 2, respectively).
    Dennis Skidds (NPS) aggregated the park-restricted data to determine whether a marsh unit is within 1 km of the cultural and historical resources. Person who carried out this activity:
    Dennis Skidds
    National Park Service
    Regional GIS Program Manager
    1 Greenhouse Rd
    Kingston, RI
    US

    401-374-4994 (voice)
    dennis_skidds@nps.gov
    Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • Cultural_1.shp
    • Cultural_2.shp
    • Cultural_3.shp
    • Cultural_4.shp
    • Cultural_5.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 18 of 20)
    Create an attribute "Arch" to denote whether a marsh unit is within 100 m of an area of archeological concern.
    SELECT BY LOCATION (intersect) [GEWA_Arch_Concern.shp] and [GEWA_SDM_Metrics.shp] to identify marsh units that are within 100 m of an area of archeological concern. If the features are within 100 m of the marsh unit, the marsh unit is assigned a value of 1. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • GEWA_Arch_Concern.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 19 of 20)
    Create an attribute "InOutPark" to denote whether a marsh unit is inside or outside of the park boundary. SELECT BY LOCATION (intersect) [NPS_boundary.shp] and [GEWA_SDM_Metrics.shp] to identify whether the marsh unit is inside or outside of the park boundary. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    • NPS_boundary.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
    Date: 2025 (process 20 of 20)
    PROJECT (Output coordinate system=WGS 1984 Web Mercator Auxiliary Sphere) [GEWA_SDM_Metrics.shp] to Web Mercator. Data sources used in this process:
    • GEWA_SDM_Metrics.shp
    Data sources produced in this process:
    • GEWA_SDM_Metrics.shp
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Marsh units, and water and land boundaries, inherit their accuracy from the vertical and horizontal accuracy of the elevation data (source of elevation data is found in Defne and others, 2023), as well as the accuracy of the wetland demarcation provided by the U.S. Fish and Wildlife Service National Wetland Inventory (USFWS NWI).
  2. How accurate are the geographic locations?
    Horizontal accuracy is inherited from the source dataset (Defne and others, 2023) that delineates the marsh units and is considered to be +/- 6 meters (m).
  3. How accurate are the heights or depths?
    Because the elevation values are averaged over delineated polygons, vertical accuracy of marsh unit elevation depends on both the horizontal accuracy of NWI dataset and the vertical accuracy of source elevation data (CoNED). CoNED vertical elevation accuracy was 0.2 m.
  4. Where are the gaps in the data? What is missing?
    The results are specific to the marsh polygons defined within the boundaries of the George Washington Birthplace National Monument (GEWA) salt marsh complex. A detailed on-the-ground analysis of a single site may result in a different interpretation of the wetland and marsh unit boundaries.
  5. How consistent are the relationships among the observations, including topology?
    Marsh units were evaluated for geoprocessing topology errors and, if found, errors were fixed and validated. The polygons were checked for correct geometry and do not overlap. A visual comparison between NAIP imagery was performed at randomly selected sites to verify the land and water boundaries. For UVVR, marsh polygons without any vegetation were assigned a value of -1. For lifespan, negative values indicate the estimated lifespan is depleted and loss is imminent and some flagged units (see description for the FLG variable) are assigned a lifespan estimate of -9999.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints. Please see 'Distribution Information' for details.
Use_Constraints Each marsh unit is defined for scientific research purposes and should not be used as a sole source of reference for any regulations and policy making. These data are marked with a Creative Commons CC0 1.0 Universal License. These data are in the public domain and do not have any use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? GEWA_SDM_Metrics.zip (ZIP file contains the shapefile GEWA_SDM_Metrics.shp and the additional shapefile components and FGDC CSDGM metadata in xml format), and a browse graphic (GEWA_SaltMarsh_Browse.png).
  3. What legal disclaimers am I supposed to read?
    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 for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 11-Dec-2025
Metadata author:
U.S. Geological Survey
Attn: Kate Ackerman
Geologist
384 Woods Hole Road
Woods Hole, MA

508-548-8700 x2331 (voice)
508-457-2310 (FAX)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with USGS.
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P13E2NM2/GEWA_SDM_Metrics.faq.html>
Generated by mp version 2.9.51 on Mon Dec 15 11:24:11 2025