Geospatial data in support of structured decision making for Boston Harbor Islands National Recreation Area, Massachusetts

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Frequently anticipated questions:

What does this data set describe?

Title:
Geospatial data in support of structured decision making for Boston Harbor Islands National Recreation Area, Massachusetts
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 Boston Harbor Islands National Recreation Area (BOHA).
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 Boston Harbor Islands National Recreation Area, Massachusetts: 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: -71.016965
    East_Bounding_Coordinate: -70.867619
    North_Bounding_Coordinate: 42.367290
    South_Bounding_Coordinate: 42.256924
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/68ac9e7fd4be0263d2491218/?name=BOHA_SaltMarsh_Browse.png&allowOpen=true (PNG)
    Graphic showing the BOHA 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 (27)
    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?
    BOHA_SDM_Metrics.shp
    Attribute information associated with marsh units of BOHA 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_MA.shp. (Source: USGS)
    Range of values
    Minimum:1838
    Maximum:3635
    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_MA.shp. (Source: USGS)
    Range of values
    Minimum:998.002
    Maximum:33699.691
    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_MA.shp. (Source: USGS)
    Range of values
    Minimum:771.639
    Maximum:27209.826
    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_MA.shp. (Source: USGS)
    Range of values
    Minimum:10
    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_MA.shp. (Source: USGS)
    Range of values
    Minimum:7
    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_MA.shp. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:9.361
    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:-0.092
    Maximum:1.44
    Units:unitless
    AMIG_M2
    Potential marsh migration area in square meters. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:49459.837
    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:3.301
    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.
    Bird
    Marsh units that intersect breeding bird nesting habitat have a value of 1, otherwise they have a value of 0. (Source: USGS)
    ValueDefinition
    1Marsh unit intersects breeding bird nesting habitat.
    0Marsh unit does not intersect breeding bird nesting habitat.
    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 Bird and SAV to indicate whether a marsh unit has breeding bird nesting habitat within the marsh unit, or SAV adjacent to the marsh unit. If both breeding bird nesting 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 breeding bird nesting habitat within the marsh unit, and SAV adjacent to the marsh unit.
    1Presence of breeding bird nesting habitat within the marsh unit, or SAV adjacent to the marsh unit.
    0Absence of breeding bird nesting 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). For BOHA, there are no buildings within 1.5 km of marsh units, therefore all marsh units have an asset score of 0. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:0
    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:0.773
    Maximum:24.210
    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
    7,598,039Total population within 50 miles of the park boundary.
    Visit
    The total number of visitors to BOHA in 2023. This value is the same for all marsh units. (Source: USGS)
    ValueDefinition
    27,986Total number of visitors to BOHA in 2023.
    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.
    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_MA.shp. (Source: USGS)
    Range of values
    Minimum:-10000
    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 Boston Harbor Islands National Recreation Area (BOHA) 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 Boston Harbor Islands National Recreation Area (BOHA) 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_MA.shp (source 1 of 21)
    Defne, Z., Ganju, N.K., and Ackerman, K.V., 2023, Lifespan of Massachusetts 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 (BOHA_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_MA.shp) into the BOHA_SDM_Metrics.shp shapefile. Downloaded in April 2024.
    relative_tidal_elevation.tif (source 2 of 21)
    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.
    marsh_migration.tif (source 3 of 21)
    National Oceanic and Atmospheric Administration (NOAA) Office for Coastal Management (OCM), 2019, NOAA Office for Coastal Management Marsh Migration: NOAA's Ocean Service, Office for Coastal Management (OCM), Charleston, SC.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Marsh migration inland boundary under sea-level rise. Downloaded the Massachusetts data in January 2024.
    NHDPlus Catchment (source 4 of 21)
    U.S. Geological Survey, 2022, National Hydrography Dataset Plus (NHD Plus): U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    NHD Plus catchment polygons for HUC 0109. Downloaded in January 2025.
    NWI.shp (source 5 of 21)
    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 Massachusetts in January 2020.
    NortheastUSDitches_Polyline.shp (source 6 of 21)
    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.
    BOHA_Veg_Poly (source 7 of 21)
    Largay, E.F., and Sneddon, L.A., 2017, Vegetation Inventory Project: Boston Harbor Islands National Recreation Area, Massachusetts. Natural Resource Report NPS/NETN/NRR—2017/1529.: National Park Service, Fort Collins, CO.

    Online Links:

    Type_of_Source_Media: digital
    Source_Contribution: Location of Phragmites in BOHA. Downloaded April 2024.
    SAV.shp (source 8 of 21)
    Boston Harbor Islands National Recreation Area, 2024, BOHA Ruppia 2024.

    Type_of_Source_Media: online
    Source_Contribution:
    At the time of publication, seagrass (ruppia) data were not publicly available from NPS. Received the data from BOHA, November 2024.
    Birds.shp (source 9 of 21)
    Boston Harbor Islands National Recreation Area, 2024, BOHA Breeding Bird Nesting Habitat.

    Type_of_Source_Media: online
    Source_Contribution:
    At the time of publication, the location of breeding bird nesting habitats were not publicly available from NPS. Received the data from BOHA, November 2024.
    BOHA_Buildings (source 10 of 21)
    Service, National Park, 2024, BOHA Built Facilities.

    Type_of_Source_Media: online
    Source_Contribution:
    At the time of publication, building locations data were not publicly available from NPS. Received the data from BOHA, November 2024.
    USGS_CCL_MaximumCCL_2022.tif (source 11 of 21)
    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_MA.shp (source 12 of 21)
    Ackerman, K.V., Defne, Z., and Ganju, N.K., 2021, Conceptual marsh units of Massachusetts salt marshes: data release DOI:10.5066/P97E086F, 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 13 of 21)
    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 14 of 21)
    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.
    Annual_Visitation (source 15 of 21)
    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 BOHA in 2023. Downloaded in August 2024.
    Cultural_1.shp (source 16 of 21)
    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 17 of 21)
    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 18 of 21)
    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 19 of 21)
    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 20 of 21)
    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.
    NPS_boundary.shp (source 21 of 21)
    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 16)
    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 16)
    Export [mu_lifespan_MA.shp] to create a new shapefile [BOHA_SDM_Metrics.shp], keeping the marsh units that are within 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 19N. 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_MA.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 3 of 16)
    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: [BOHA_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 [BOHA_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:
    • BOHA_SDM_Metrics.shp
    • relative_tidal_elevation.tif
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 4 of 16)
    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.
    This process step followed the methodology detailed in "Chesapeake Bay marsh migration potential under sea-level rise" (Defne and others, 2025), and used these input datasets for BOHA: (1) Marsh migration datasets for Massachusetts [marsh_migration.tif] (2) NHD datasets for HUC 0109 [NHDPlus Catchment].
    The migration space is based on the NOAA marsh migration predictions under 2 feet of local sea-level rise and divided into smaller parcels by using the National Hydrography Dataset Plus (NHD Plus) catchments. The marsh migration space is then distributed to the marsh units. Data sources used in this process:
    • BOHA_SDM_Metrics.shp
    • marsh_migration.tif
    • NHDPlus Catchment
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 5 of 16)
    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 [BOHA_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:
    • BOHA_SDM_Metrics.shp
    • NWI.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 6 of 16)
    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 [BOHA_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:
    • BOHA_SDM_Metrics.shp
    • NortheastUSDitches_Polyline.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2024 (process 7 of 16)
    Create attribute "Phrag" that indicates the presence or absence of Phragmites in the marsh unit.
    SELECT BY LOCATION (intersect) [BOHA_Veg_Poly] and [BOHA_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:
    • BOHA_SDM_Metrics.shp
    • BOHA_Veg_Poly
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 8 of 16)
    Create attribute "BioDiv" that provides information on the biodiversity of the marsh unit, which is the summation of the "Bird" (whether the marsh unit intersects a breeding bird nesting habitat) and the "SAV" (whether the marsh unit is within 100m of seagrass beds) attributes.
    Bird: SELECT BY LOCATION (intersect) [Birds.shp] and [BOHA_SDM_Metrics.shp] to identify marsh units that intersect breeding bird nesting habitat. If they do, the marsh unit is assigned a value of 1 for the “Bird” attribute.
    SAV: SELECT BY LOCATION (intersect, 100 m) [SAV.shp] and [BOHA_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 “Bird” and “SAV” attributes. Data sources used in this process:
    • BOHA_SDM_Metrics.shp
    • Birds.shp
    • SAV.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 9 of 16)
    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:
    • BOHA_SDM_Metrics.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 10 of 16)
    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). Note that for BOHA, there are no buildings within 1.5 km of marsh units, therefore all marsh units have an asset score of 0. The process steps are included here for completeness.
    1)PROJECT source shapefiles from WGS 1984 Web Mercator coordinate system to NAD 83 (2011) UTM 19N and output as feature classes within a geodatabase to ensure distance calculations are accurate. Source files: marsh units: [BOHA_SDM_Metrics]; buildings: [BOHA_Buildings]; output: [BOHA_BuildingFeatures_UTM19].
    2)Calculate the maximum CCL value within 100 m of each of the assets (buildings) within BOHA boundary. BUFFER [BOHA_BuildingFeatures_UTM19] by 100 m, output= [BOHA_BID100mBuff]. ZONAL STATISTICS AS TABLE (Input: [BOHA_BID100mBuff]; zone field=BID; Input Value Raster: [USGS_CCL_2022.tif]; Output table: [BOHA_BuildingMaxCCL_100m]; Statistics Type=Maximum).
    3)Calculate the distance in meters from the buildings [BOHABuildingFeatures_UTM19] to the closest point along the boundary of all marsh units [BOHA_SDM_Metrics] that are within 1 km of each feature in [BOHABuildingFeatures_UTM19]. GENERATE NEAR TABLE (Output table: [BOHA_BuildingsNearMU_1km]). Only need to retain the fields "IN_FID", "NEAR_FID", and "NEAR_DIST" from the output table. Note that for BOHA, there are no buildings within 1 km of marsh units.
    4)Join (JOIN FIELD) the MAX CCL value from table [BOHA_BuildingMaxCCL_100m] (join field=BID) to the output table [BOHA_BuildingsNearMU_1km] (join field=IN_FID; Transfer Fields=MAX).
    5)ADD FIELDS (multiple) (Input Table: [BOHA_SDM_Metrics]; Field Names: "Dist" (Short) and "AssetScore" (Double)).
    6)ADD JOIN (Join one to many) (Input Table: [BOHA_SDM_Metrics]; input field=OBJECTID; Join Table: [BOHA_BuildingsNearMU_1km]; Join Field: NEAR_FID; transfer all fields). EXPORT joined feature class to [BOHA_SDM_Metrics_AS].
    7) Calculate the "AssetScore" field in 2 steps. In [BOHA_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: [BOHA_SDM_Metrics_AS]; Dissolve field: FID_CMU; Statistics field: AssetScore; Statistics Type: Maximum; Output: [BOHA_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 [BOHA_SDM_Metrics_AS] and only retains "FID_CMU" and "MAX_AssetScore."
    9)JOIN FIELD "MAX_AssetScore" from [BOHA_SDM_Metrics_AS] back into original source [BOHA_SDM_Metrics.shp] using the "FID_CMU" field. Data sources used in this process:
    • BOHA_SDM_Metrics.shp
    • BOHA_Buildings
    • USGS_CCL_MaximumCCL_2022.tif
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 11 of 16)
    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_MA.shp] that are within and adjacent to the park boundary [NPS_boundary.shp] where "TYP"= 'vegetated'; output: [CMU_BOHA_VEG.shp]. PROJECT [CMU_BOHA_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_BOHA_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_BOHA_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:
    • BOHA_SDM_Metrics.shp
    • CMU_MA.shp
    • NPS_boundary.shp
    • BiomassC_CONUSTidalMarshes_gCm2.tif
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 12 of 16)
    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 [BOHA_SDM_Metrics.shp]. Calculate total population in the selected census blocks. Data sources used in this process:
    • BOHA_SDM_Metrics.shp
    • Census_Blocks.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 13 of 16)
    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 BOHA in 2023 was obtained from [Annual_Visitation]. Data sources used in this process:
    • BOHA_SDM_Metrics.shp
    • Annual_Visitation
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2024 (process 14 of 16)
    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:
    • BOHA_SDM_Metrics.shp
    • Cultural_1.shp
    • Cultural_2.shp
    • Cultural_3.shp
    • Cultural_4.shp
    • Cultural_5.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 15 of 16)
    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 [BOHA_SDM_Metrics.shp] to identify whether the marsh unit is inside or outside of the park boundary. Data sources used in this process:
    • BOHA_SDM_Metrics.shp
    • NPS_boundary.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
    Date: 2025 (process 16 of 16)
    PROJECT (Output coordinate system=WGS 1984 Web Mercator Auxiliary Sphere) [BOHA_SDM_Metrics.shp] to Web Mercator. Data sources used in this process:
    • BOHA_SDM_Metrics.shp
    Data sources produced in this process:
    • BOHA_SDM_Metrics.shp
  3. What similar or related data should the user be aware of?
    Defne, Z., Ackerman, K.V., Andrews, B.D., and Ganju, N.K., 2025, Chesapeake Bay marsh migration potential under sea-level rise: 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:

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 Boston Harbor Islands National Recreation Area (BOHA) 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? BOHA_SDM_Metrics.zip (ZIP file contains the shapefile BOHA_SDM_Metrics.shp and the additional shapefile components and FGDC CSDGM metadata in xml format), and browse graphic (BOHA_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/BOHA_SDM_Metrics.faq.html>
Generated by mp version 2.9.51 on Mon Dec 15 11:24:11 2025