Metadata:
  Identification_Information:
    Citation:
      Citation_Information:
        Originator: Zafer Defne
        Originator: Kate V. Ackerman
        Originator: Brian D. Andrews
        Originator: Neil K. Ganju
        Publication_Date: 20250218
        Title: Metrics for marsh migration under sea-level rise in Chesapeake Bay
        Edition: 1.0
        Geospatial_Data_Presentation_Form: Vector Digital Data Set (Polygon)
        Series_Information:
          Series_Name: data release
          Issue_Identification: DOI:10.5066/P18BWN2U
        Publication_Information:
          Publication_Place: Reston, Virginia
          Publisher: U.S. Geological Survey
        Other_Citation_Details: Suggested citation: Defne, Z., Ackerman, K.V., Andrews, B.D., and Ganju, N.K., 2025, Chesapeake Bay marsh migration potential under sea-level rise: U.S. Geological Survey data release, https://doi.org/10.5066/P18BWN2U.
        Online_Linkage: https://doi.org/10.5066/P18BWN2U
        Online_Linkage: https://www.sciencebase.gov/catalog/item/677d4d5dd34e480c9507fa29
        Larger_Work_Citation:
          Citation_Information:
            Originator: Zafer Defne
            Originator: Kate V. Ackerman
            Originator: Brian D. Andrews
            Originator: Neil K. Ganju
            Publication_Date: 2025
            Title: Chesapeake Bay marsh migration potential under sea-level rise
            Edition: 1
            Geospatial_Data_Presentation_Form: dataset
            Series_Information:
              Series_Name: data release
              Issue_Identification: DOI:10.5066/P18BWN2U
            Publication_Information:
              Publication_Place: Reston, VA
              Publisher: U.S. Geological Survey
            Other_Citation_Details: Suggested citation: Defne, Z., Ackerman, K.V., Andrews, B.D., and Ganju, N.K., 2025, Chesapeake Bay marsh migration potential under sea-level rise: U.S. Geological Survey data release, https://doi.org/10.5066/P18BWN2U.
    Description:
      Abstract:
        Marsh migration potential in the Chesapeake Bay (CB) salt marshes is calculated in terms of available migration area for each marsh unit defined by Ackerman and others (2022). The space available for landward migration is based on the NOAA marsh migration predictions under 2.0 feet of local sea-level rise (SLR). The migration space is further divided by National Hydrography Dataset (NHD) Plus catchments before assigning related catchment polygons to each marsh unit. The migration rates are then calculated using present day estimates at the prescribed rate of SLR, which correspond to the 0.3, 0.5, and 1.0 meter increase in Global Mean Sea Level (GMSL) scenarios by 2100 from Sweet and others (2022). Through scientific efforts, the U.S. Geological Survey has been expanding national assessment of coastal change hazards and forecast products to coastal wetlands, including the Chesapeake Bay salt marshes, with the intent of providing Federal, State, and local managers with tools to estimate the vulnerability and ecosystem service potential of these wetlands. For this purpose, the response and resilience of coastal wetlands to physical factors need to be assessed in terms of the ensuing change to their vulnerability and ecosystem services. Marsh migration is one of the natural responses to SLR. 

        References:
        Ackerman, K.V., Defne, Z., and Ganju, N.K., 2022, Geospatial characterization of salt marshes in Chesapeake Bay: U.S. Geological Survey data release, https://doi.org/10.5066/P997EJYB.

        Sweet, W.V., Hamlington, B.D., Kopp, R.E., Weaver, C.P., Barnard, P.L., Bekaert, D., Brooks, W., Craghan, M., Dusek, G., Frederikse, T., Garner, G., Genz, A.S., Krasting, J.P., Larour, E., Marcy, D., Marra, J.J., Obeysekera, J., Osler, M., Pendleton, M., Roman, D., Schmied, L., Veatch, W., White, K.D., and Zuzak, C., 2022, Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines. NOAA Technical Report NOS 01. National Oceanic and Atmospheric Administration, National Ocean Service, Silver Spring, MD, 111 pp.
      Purpose: The purpose of this shapefile is to present the landward migration metrics for each marsh unit in Chesapeake Bay.
    Time_Period_of_Content:
      Time_Period_Information:
        Single_Date/Time:
          Calendar_Date: 2025
      Currentness_Reference: publication date
    Status:
      Progress: Complete
      Maintenance_and_Update_Frequency: None
    Spatial_Domain:
      Bounding_Coordinates:
        West_Bounding_Coordinate: -77.3747
        East_Bounding_Coordinate: -75.5934
        North_Bounding_Coordinate: 39.5898
        South_Bounding_Coordinate: 36.3744
    Keywords:
      Theme:
        Theme_Keyword_Thesaurus: ISO 19115 Topic Category
        Theme_Keyword: oceans
        Theme_Keyword: inlandWaters
        Theme_Keyword: environment
        Theme_Keyword: elevation
      Theme:
        Theme_Keyword_Thesaurus: USGS Thesaurus
        Theme_Keyword: geospatial datasets
        Theme_Keyword: wetland ecosystems
        Theme_Keyword: wetland functions
        Theme_Keyword: coastal ecosystems
        Theme_Keyword: coastal processes
        Theme_Keyword: sea-level change
        Theme_Keyword: sediment transport
        Theme_Keyword: estuarine processes
        Theme_Keyword: vegetation
      Theme:
        Theme_Keyword_Thesaurus: None
        Theme_Keyword: salt marsh
        Theme_Keyword: marsh health
        Theme_Keyword: lifespan
        Theme_Keyword: estuary
        Theme_Keyword: Long-Term Ecological Research
        Theme_Keyword: LTER
      Theme:
        Theme_Keyword_Thesaurus: USGS Metadata Identifier
        Theme_Keyword: USGS:677d4d5dd34e480c9507fa29
      Place:
        Place_Keyword_Thesaurus: CommonGeographicAreas
        Place_Keyword: Atlantic
        Place_Keyword: United States
        Place_Keyword: Maryland
        Place_Keyword: Virginia
        Place_Keyword: Chesapeake
    Access_Constraints: None
    Use_Constraints: The migration potential for 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. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the source of this information.
    Point_of_Contact:
      Contact_Information:
        Contact_Organization_Primary:
          Contact_Organization: U.S. Geological Survey
          Contact_Person: Zafer Defne
        Contact_Position: Oceanographer
        Contact_Address:
          Address_Type: mailing and physical address
          Address: 384 Woods Hole Road
          City: Woods Hole
          State_or_Province: MA
          Postal_Code: 02543
        Contact_Voice_Telephone: 508-548-8700 x2254
        Contact_Facsimile_Telephone: 508-457-2310
        Contact_Electronic_Mail_Address: zdefne@usgs.gov
    Browse_Graphic:
      Browse_Graphic_File_Name: https://www.sciencebase.gov/catalog/file/get/677d4d5dd34e480c9507fa29?name=mu_migration_CB.png&allowOpen=true
      Browse_Graphic_File_Description: Total marsh migration area for each marsh unit under 2-feet of SLR in Chesapeake Bay overlaying Esri basemap.
      Browse_Graphic_File_Type: PNG
    Native_Data_Set_Environment: Environment as of Metadata Creation: Microsoft Windows 10 Version 0.1 (Build 19042); Esri ArcGIS Pro 3.3.2
    Cross_Reference:
      Citation_Information:
        Originator: Kate V. Ackerman
        Originator: Zafer Defne
        Originator: Neil K. Ganju
        Publication_Date: 2022
        Title: Geospatial characterization of salt marshes in Chesapeake Bay
        Edition: 1.0
        Geospatial_Data_Presentation_Form: dataset
        Series_Information:
          Series_Name: data release
          Issue_Identification: DOI:10.5066/P997EJYB
        Publication_Information:
          Publication_Place: Reston, VA
          Publisher: U.S. Geological Survey
        Online_Linkage: https://doi.org/10.5066/p997ejyb
    Cross_Reference:
      Citation_Information:
        Originator: National Oceanic and Atmospheric Administration, National Ocean Service
        Publication_Date: 2022
        Title: Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines. NOAA Technical Report NOS 01, 111 pp.
        Geospatial_Data_Presentation_Form: publication
        Publication_Information:
          Publication_Place: Silver Spring, MD
          Publisher: National Oceanic and Atmospheric Administration
        Online_Linkage: https://oceanservice.noaa.gov/hazards/sealevelrise/Sea_Level_Rise_Datasets_2022.zip
        Online_Linkage: https://sealevel.globalchange.gov/internal_resources/756/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf
  Data_Quality_Information:
    Attribute_Accuracy:
      Attribute_Accuracy_Report: Marsh units, water and land boundaries inherit their accuracy from accuracy of the source data, Chesapeake Bay marsh units. Landward migration boundaries inherit accuracy from the source data; USGS National Hydrography Dataset (NHD) Plus Catchment and NOAA Office for Coastal Management Marsh Migration raster datasets. These boundaries are used in calculation of area available for migration. Migration rates are calculated based on the local estimated sea-level rise by 2100 given by the NOAA technical report (Sweet and others, 2022).
    Logical_Consistency_Report: Migration potential is zero for a marsh unit that is not connected to any migration area.
    Completeness_Report: The results are specific to the marsh polygons definition within the boundaries of the Chesapeake Bay 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.
    Positional_Accuracy:
      Horizontal_Positional_Accuracy:
        Horizontal_Positional_Accuracy_Report: Horizontal accuracy is inherited from the source datasets; the marsh units, and the boundaries of marsh migration inherit from the NOAA migration raster datasets.
      Vertical_Positional_Accuracy:
        Vertical_Positional_Accuracy_Report: Dataset has no vertical values.
    Lineage:
      Source_Information:
        Source_Citation:
          Citation_Information:
            Originator: Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Office for Coastal Management (OCM)
            Publication_Date: 201907
            Title: NOAA Office for Coastal Management Marsh Migration
            Geospatial_Data_Presentation_Form: raster digital data
            Publication_Information:
              Publication_Place: Charleston, SC
              Publisher: NOAA's Ocean Service, Office for Coastal Management (OCM)
            Online_Linkage: https://coast.noaa.gov/slr
            Online_Linkage: https://coast.noaa.gov/digitalcoast/data/slr-wetland.html
        Type_of_Source_Media: Digital
        Source_Time_Period_of_Content:
          Time_Period_Information:
            Single_Date/Time:
              Calendar_Date: 2016
          Source_Currentness_Reference: ground condition
        Source_Citation_Abbreviation: md_marshmigration_2016.zip
        Source_Contribution: Marsh migration inland boundary under sea-level rise
      Source_Information:
        Source_Citation:
          Citation_Information:
            Originator: Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Office for Coastal Management (OCM)
            Publication_Date: 201907
            Title: NOAA Office for Coastal Management Marsh Migration
            Geospatial_Data_Presentation_Form: raster digital data
            Publication_Information:
              Publication_Place: Charleston, SC
              Publisher: NOAA's Ocean Service, Office for Coastal Management (OCM)
            Online_Linkage: https://coast.noaa.gov/slr
            Online_Linkage: https://coast.noaa.gov/digitalcoast/data/slr-wetland.html
        Type_of_Source_Media: Digital
        Source_Time_Period_of_Content:
          Time_Period_Information:
            Single_Date/Time:
              Calendar_Date: 2016
          Source_Currentness_Reference: ground condition
        Source_Citation_Abbreviation: va_marshmigration_2016.zip
        Source_Contribution: Marsh migration inland boundary under sea-level rise
      Source_Information:
        Source_Citation:
          Citation_Information:
            Originator: Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Office for Coastal Management (OCM)
            Publication_Date: 201907
            Title: NOAA Office for Coastal Management Marsh Migration
            Geospatial_Data_Presentation_Form: raster digital data
            Publication_Information:
              Publication_Place: Charleston, SC
              Publisher: NOAA's Ocean Service, Office for Coastal Management (OCM)
            Online_Linkage: https://coast.noaa.gov/slr
            Online_Linkage: https://coast.noaa.gov/digitalcoast/data/slr-wetland.html
        Type_of_Source_Media: Digital
        Source_Time_Period_of_Content:
          Time_Period_Information:
            Single_Date/Time:
              Calendar_Date: 2016
          Source_Currentness_Reference: ground condition
        Source_Citation_Abbreviation: nc_marshmigration_2016.zip
        Source_Contribution: Marsh migration inland boundary under sea-level rise
      Source_Information:
        Source_Citation:
          Citation_Information:
            Originator: National Oceanic and Atmospheric Administration, National Ocean Service
            Publication_Date: 2022
            Title: Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines. NOAA Technical Report NOS 01, 111 pp.
            Geospatial_Data_Presentation_Form: dataset
            Publication_Information:
              Publication_Place: Silver Spring, MD
              Publisher: National Oceanic and Atmospheric Administration
            Online_Linkage: https://oceanservice.noaa.gov/hazards/sealevelrise/Sea_Level_Rise_Datasets_2022.zip
            Online_Linkage: https://sealevel.globalchange.gov/internal_resources/756/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf
        Type_of_Source_Media: Digital
        Source_Time_Period_of_Content:
          Time_Period_Information:
            Single_Date/Time:
              Calendar_Date: 2022
          Source_Currentness_Reference: ground condition
        Source_Citation_Abbreviation: SLR data
        Source_Contribution: Sea-level rise projections for 2100 for selected scenarios
      Source_Information:
        Source_Citation:
          Citation_Information:
            Originator: Kate Ackerman
            Originator: Zafer Defne
            Originator: Neil Kamal Ganju
            Publication_Date: 2022
            Title: Geospatial characterization of salt marshes in Chesapeake Bay
            Geospatial_Data_Presentation_Form: dataset
            Series_Information:
              Series_Name: data release
              Issue_Identification: DOI:10.5066/P997EJYB
            Publication_Information:
              Publication_Place: https://www.sciencebase.gov
              Publisher: U.S. Geological Survey
            Online_Linkage: https://doi.org/10.5066/p997ejyb
            Online_Linkage: https://www.sciencebase.gov/catalog/item/630f9ba4d34e36012efa0924
        Type_of_Source_Media: Digital and/or Hardcopy
        Source_Time_Period_of_Content:
          Time_Period_Information:
            Single_Date/Time:
              Calendar_Date: 2022
          Source_Currentness_Reference: publication date
        Source_Citation_Abbreviation: mu_UVVR_CB.shp
        Source_Contribution: Marsh units outlines
      Source_Information:
        Source_Citation:
          Citation_Information:
            Originator: U.S. Geological Survey
            Publication_Date: 20220324
            Title: National Hydrography Dataset (NHD)
            Geospatial_Data_Presentation_Form: vector digital data
            Publication_Information:
              Publication_Place: Reston, Virginia
              Publisher: U.S. Geological Survey
            Online_Linkage: https://www.usgs.gov/core-science-systems/ngp/national-hydrography
        Type_of_Source_Media: Digital and/or Hardcopy
        Source_Time_Period_of_Content:
          Time_Period_Information:
            Single_Date/Time:
              Calendar_Date: 20220324
          Source_Currentness_Reference: publication date
        Source_Citation_Abbreviation: NHDPlusCatchment
        Source_Contribution: NHD Plus Catchment polygons
      Process_Step:
        Process_Description:
          This process step and subsequent process steps were performed by the same person, Zafer Defne, in ArcGIS Pro (ver.3.3.2) unless otherwise stated. For complex operations, names of specific tools used are given in CAPITAL letters (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.

          This processing step defines the extent of migration area.

          a) Download the NOAA Sea level rise wetland impacts and migration datasets for the Chesapeake Bay domain [md_marshmigration_2016.zip, va_marshmigration_2016.zip, nc_marshmigration_2016.zip]. These datasets present the potential distribution of each wetland type based on their elevation and frequency of inundation under different SLR rates. Use four scenarios: 0.5, 1.0, 1.5, 2.0 feet of SLR as input. 

          b) From each scenario select classes of Palustrine Emergent Wetland (15), Brackish/Transition Wetland (17), Estuarine Wetland (18) by EXTRACT_BY_ATTRIBUTES(VALUE = 15 Or VALUE = 17 Or VALUE = 18).

          c) Mosaic all four rasters from previous step into to a new raster for Maryland (MD) while setting the coordinate system to NAD1983 (2011) UTM Zone 18N. MOSAIC_TO_NEW_RASTER(Pixel Type="1bit"; Spatial Reference=NAD_1983_2011_UTM_Zone_18N; Mosaic Operator="Maximum"). Export only the values greater than 1 as a new raster and convert to polygon. RASTER_TO_POLYGON(Field = "VALUE").

          Repeat the same steps for Virginia (VA) and North Carolina (NC) domains. And merge the results in to a single feature dataset [mm_MD_VA_NC_merge_UTM18_2011.shp].
        Source_Used_Citation_Abbreviation: md_marshmigration_2016.zip
        Source_Used_Citation_Abbreviation: va_marshmigration_2016.zip
        Source_Used_Citation_Abbreviation: nc_marshmigration_2016.zip
        Process_Date: 2024
        Source_Produced_Citation_Abbreviation: mm_MD_VA_NC_merge_UTM18_2011.shp
        Process_Contact:
          Contact_Information:
            Contact_Organization_Primary:
              Contact_Organization: U.S. Geological Survey
              Contact_Person: Zafer Defne
            Contact_Position: Oceanographer
            Contact_Address:
              Address_Type: mailing and physical address
              Address: 384 Woods Hole Road
              City: Woods Hole
              State_or_Province: MA
              Postal_Code: 02543
            Contact_Voice_Telephone: 508-548-8700 x2254
            Contact_Facsimile_Telephone: 508-457-2310
            Contact_Electronic_Mail_Address: zdefne@usgs.gov
      Process_Step:
        Process_Description:
          This processing step delineates the migration area based on the USGS National Hydrography Dataset Plus High Resolution (NHD Plus HR) catchments map. First, the catchments intersecting the marsh units are selected as immediate catchments. Then, if the inland boundary of the migration layer spans across multiple catchments, those catchments are merged to the immediate catchments by proximity. Catchments areas beyond the inland boundary of migration layer are clipped to the boundary. The resulting product is the marsh migration polygons which is the migration zone delineated with catchments. 

          a) Download Chesapeake Bay marsh units dataset [mu_UVVR_CB.shp] and NHD Plus HR catchments datasets for the domain. [mu_UVVR_CB.shp];  NHDPlusCatchment feature datasets [NHDPlusCatchment_0206.shp], [NHDPlusCatchment_0207.shp], [NHDPlusCatchment_0208.shp] and [NHDPlusCatchment_0301.shp].

          b) Project all source feature datasets to the same coordinate system with the previous processing step, NAD1983 (2011) UTM Zone 18N. Resulting projected data sets are: Marsh units [mu_UVVR_CB_UTM18_2011.shp];  NHDPlusCatchment feature datasets [NHDPlusCatchment_0206_UTM18_2011.shp], [NHDPlusCatchment_0207_UTM18_2011.shp], [NHDPlusCatchment_0208_UTM18_2011.shp] and [NHDPlusCatchment_0301_UTM18_2011.shp]

          c) Merge all catchment feature datasets to create the total catchment area [HDPlusCatchment_merge_0206_0207_0208_0301.shp].

          d) Select parts of migration area that intersect with marsh units. SELECT_LAYER_BY_LOCATION(Input features=mm_MD_VA_NC_merge_UTM18_2011.shp; Selecting features=mu_UVVR_CB_UTM18_2011.shp; Relationship=Intersect; Search distance =1 meter). Export features as [mmp_by_mu.shp].

          e) SELECT_LAYER_BY_LOCATION(Input features=HDPlusCatchment_merge_0206_0207_0208_0301.shp; Selecting features= mmp_by_mu.shp, Relationship=Intersect). Export features as [cathments_selected.shp].

          f) Intersect the two feature datasets to identify the immediate catchment polygons. PAIRWISE_INTERSECT(Input features=catchments_selected.shp, mmp_by_mu.shp ). Export features as [mmp_iniside_cat.shp].

          g) Remove the immediate catchments from the overall marsh migration area so that the catchments in the migration area but beyond the immediate ones can be processed. PAIRWISE_ERASE(Input features=mm_MD_VA_NC_merge_UTM18_2011.shp; Erase features=mmp_inside_cat.shp; Output=mm_outside_cat.shp). MULTIPART_TO_SINGLEPART(Input features=mm_outside_cat.shp; Output features=mm_outside_cat_single.shp) and SELECT_LAYER_BY_LOCATION(Input features=mm_outside_cat_single.shp; Selecting features=mu_UVVR_CB_UTM18_2011.shp; Relationship=Intersect; Search distance =1 meter). Export features as [mmp_outside_cat.shp].

          h) Union the immediate catchments with the remote catchments to create a union set of catchments. UNION(Input features=mmp_iniside_cat.shp, mmp_outside_cat.shp; Gaps allowed=Yes, Output features=mmp_all.shp). 

          i) Prepare and split the union of catchments to immediate catchments and remote catchments so that the remote catchments can be merged by proximity. Specifically, ERASE marsh units from the union of catchments and MULTIPART_TO_SINGLEPART to obtain [mmp_all_single.shp]. Create two feature datasets from this dataset: For immediate catchments SELECT_LAYER_BY_LOCATION(Input features=mmp_all_single.shp; Selecting features=mu_UVVR_CB_UTM18_2011.shp; Relationship=Intersect; Search distance=0.001 meter) and export as [input_mmu.shp]. For remote catchments SELECT_LAYER_BY_LOCATION(Input features=mmp_all_single.shp; Selecting features=mu_UVVR_CB_UTM18_2011.shp; Relationship=Intersect; Search distance=0.001 meter, Invert Spatial Relationship=Yes) and export as [near_mmu.shp].

          j) Run the HYDUNITLOOP tool to merge catchments. At each iteration step, the script uses NEAR tool to find remote catchments from the [input_mmu.shp] within 1 meter of an immediate catchment [near_mmu.shp] and merges them to it using UNION and DISSOLVE tools. The catchments merged with an immediate catchment are removed from the remote catchments dataset. The script iterates until there is no change in the number of remote and immediate units. The remaining catchments are those that are more than 1 meter away from any immediate ones and they are discarded. The resulting final dataset is [final_mmu.shp]. HYDUNITLOOP(Input features=input_mmu.shp; Near features=near_mmu.shp; Output features=final_mmu.shp].

          k) Because of the resolution difference between the datasets, processing sometimes creates sliver polygons around the edges. To clean up the final output, remove detached marsh migration polygons with area smaller than a threshold value. Specifically, first PAIRWISE_DISSOLVE(Input features=final_mmu.shp; Output feature class=final_mmu_diss.shp) and CALCULATE_GEOMETRY_ATTRIBUTES(Input features=final_mmu_diss.shp; Geometry attributes field=ASQM; Property=Area (geodesic); Area unit=Square meters; Coordinate system=NAD_1983_2011_Contiguous_USA_Albers). Then, select polygons with areas greater than 300 square meter to export [fmmu_gt_300.shp] and use them to select from [final_mmu.shp] dataset by SELECT_BY_LOCATION(Input feature=final_mmu.shp; Relationship=Within; Selecting features=fmmu_gt_300.shp; Search distance=0 meters). Finally, export the selected features as [marsh_migration_polygons.shp].
        Source_Used_Citation_Abbreviation: mm_MD_VA_NC_merge_UTM18_2011.shp
        Source_Used_Citation_Abbreviation: mu_UVVR_CB.shp
        Source_Used_Citation_Abbreviation: NHDPlusCatchment
        Process_Date: 2024
        Source_Produced_Citation_Abbreviation: marsh_migration_polygons.shp
      Process_Step:
        Process_Description:
          Calculate total marsh migration area, ratio of total migration area to marsh unit area and migration rate.

          Total migration area for a marsh unit is calculated as the sum of all catchment areas within in the migration zone that the marsh unit borders, where catchments are clipped to the SLR extent landward. If same migration area is bounded by multiple marsh units then the marsh area proportioned by the length of the shared boundary between the migration area and each unit. 

          Marsh migration rate for each unit is defined as the migration area covered per year by that marsh unit under a SLR scenario. Similar to total area calculation, if same migration area is shared by multiple marsh units a migration rate is calculated per each migration area proportional to the shared boundary. However, if multiple catchments are within the total marsh migration area, the maximum of the migration rates is assigned as the final migration rate. 

          a) First, calculate the migration rate in in terms of area per time by dividing the migration area for each unit by the time it takes for a SLR of 2 feet. This step is done in MATLAB (version 2021b). For sea-level rise projections Sweet and others (2022) SLR data within the region were used. A total of 40 points including 20 stations and 20 grid points were within the bounding box with lower left corner of (-78.0000N, 35.7950W) and upper right corner of (-74.9600N, 40.0000W). SLR rate is calculated as SLR_RATE=(RSL2100+RSL_OFFSET)/100-RSL_VLM, where RSL2100 is the relative sea level  by 2100 under a global mean sea level rise scenario, RSL_OFFSET is the offset to initiate the projection at year 2000, and RSL_VLM is the relative sea level contribution from vertical land motion. Interpolate the SLR_RATE from 40 points over a regular grid using GRIDDATA function with natural neighbor interpolation (grid size of 30 longitudinal by 42 latitudinal points). Assign to each marsh migration polygon the interpolated SLR_RATE value from the nearest grid point. For each polygon, calculate the time it takes for a SLR of 2 feet by dividing the migration area by the SLR_RATE. Do this for the three scenarios considered: GMSL rise of 0.3 meters, 0.5 meters and 1.0 meters by year 2100. Join these values to the marsh migration polygons table as YRS03, YRS05, YRS10, respectively. 

          Sweet, W.V., Hamlington, B.D., Kopp, R.E., Weaver, C.P., Barnard, P.L., Bekaert, D., Brooks, W., Craghan, M., Dusek, G., Frederikse, T., Garner, G., Genz, A.S., Krasting, J.P., Larour, E., Marcy, D., Marra, J.J., Obeysekera, J., Osler, M., Pendleton, M., Roman, D., Schmied, L., Veatch, W., White, K.D., and Zuzak, C., 2022, Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines. NOAA Technical Report NOS 01. National Oceanic and Atmospheric Administration, National Ocean Service, Silver Spring, MD, 111 pp.

          b) Next, add a new field to marsh migration polygons dataset to transfer their FID info to the shared boundary segments. CALCULATE_FIELD(Input table=marsh_migration_polgons.shp; Field name=FID_MM; Field Type=Long; Expression="FID_MM=!FID!"). Then intersect the marsh units and the marsh polygons to calculate the length of each shared boundary.  INTERSECT(Input features=mu_UVVR_CB.shp, marsh_migration_polygons.shp; Output feature=MM_MU_boundary.shp; Output type=Line). Calculate the length of each boundary segment with CALCULATE_GEOMETRY_ATTRIBUTES(Input features=MM_MU_boundary.shp; Geometry attributes field=M_L; Property=Length(geodesic); Length units=Meters; Coordinate system=NAD_1983_2011_UTM_Zone_18N).

          c) Delete field FID_MM from marsh migration polygons and spatial join with the shared boundary dataset to create marsh polygons with boundary segment lengths. SPATIAL_JOIN(Target features=marsh_migration_polygons.shp; Join features=MM_MU_boundary.shp; Output feature class=MM_MU_boundary_len.shp; Join operation=One to many; Match option=Intersect; Fields=FID_MM,FID_CMU,M_L,YRS03,YRS05,YRS10). SELECT(Input features=MM_MU_boundary_len.shp; Output feature class=MM_MU_boundary_len_Select.shp; Where=TARGET_FID is equal to FID_MM).

          d) Calculate marsh migration area associated with each boundary segment by CALCULATE_GEOMETRY_ATTRIBUTES(Input features=MM_MU_boundary_len_Select.shp; Geometry attributes field=MM_A; Property=Area (geodesic); Area unit=Square meters; Coordinate system=NAD_1983_2011_Contiguous_USA_Albers) and SUMMARY_STATISTICS(Input table=MM_MU_boundary_len_Select.shp; Output table=M_L_sum_by_MM.dbf; Statistics field property=M_L; Statistics type=Sum; Case field=TARGET_FID) and JOIN_FIELD(Input table=MM_MU_boundary_len_Select.shp; Input field=TARGET_FID; Join table=M_L_sum_by_MM.dbf; Join field=TARGET_FID; Transfer method=Use field mapping; Field map=TARGET_FID, SUM_M_L; Index join fields=Do not add indexes).

          e) Calculate potential marsh migration area associated with each marsh unit by CALCULATE_FIELD(Input table=MM_MU_boundary_len_Select.shp; Field name=PMA; Expression="!M_L! / !SUM_M_L! * !MM_A!") and then PAIRWISE_DISSOLVE(Input features=MM_MU_boundary_len_Select.shp; Output feature class=MM_MU_boundary_area_summary.shp; Dissolve fields=FID_CMU; Statistics fields=PMA; Statistics type=Sum; Create multipart features=Yes).

          f) Finally, create the marsh migration dataset by joining the migration summary dataset to the UVVR dataset. Also calculate a ratio of migration area to marsh unit are at this step. JOIN_FIELD(Input table=mu_UVVR_CB.shp; Input field=FID_CMU; Join table=MM_MU_boundary_area_summary.shp; Join field=FID_CMU; Transfer method=Use field mapping; FieldMap:AMIG_M2,MIGR03,MIGR05,MIGR10). CALCULATE_FIELD(Input table=mu_UVVR_CB.shp; Field name=AMIGRAT; Expression="!AMIG_M2!/!ATOT_M2!"). Keep only FID_CMU, ATOT_M2, AVEG_M2, AMIG_M2, FLG fields and the transferred fields, and export features as mu_migration_CB.shp.
        Source_Used_Citation_Abbreviation: marsh_migration_polygons.shp
        Source_Used_Citation_Abbreviation: mu_UVVR_CB.shp
        Process_Date: 2024
        Source_Produced_Citation_Abbreviation: mu_migration_CB.shp
  Spatial_Data_Organization_Information:
    Direct_Spatial_Reference_Method: Vector
    Point_and_Vector_Object_Information:
      SDTS_Terms_Description:
        SDTS_Point_and_Vector_Object_Type: G-polygon
        Point_and_Vector_Object_Count: 46457
  Spatial_Reference_Information:
    Horizontal_Coordinate_System_Definition:
      Planar:
        Map_Projection:
          Map_Projection_Name: WGS 1984 Web Mercator Auxiliary Sphere (ESRI Full Name: WGS_1984_Web_Mercator_Auxiliary_Sphere)
          Mercator:
            Standard_Parallel: 0.0
            Longitude_of_Central_Meridian: 0.0
            False_Easting: 0.0
            False_Northing: 0.0
        Planar_Coordinate_Information:
          Planar_Coordinate_Encoding_Method: coordinate pair
          Coordinate_Representation:
            Abscissa_Resolution: 0.6096
            Ordinate_Resolution: 0.6096
          Planar_Distance_Units: meters
      Geodetic_Model:
        Horizontal_Datum_Name: D_WGS_1984
        Ellipsoid_Name: WGS_1984
        Semi-major_Axis: 6378137.0
        Denominator_of_Flattening_Ratio: 298.257223563
  Entity_and_Attribute_Information:
    Detailed_Description:
      Entity_Type:
        Entity_Type_Label: mu_migration_CB.shp Attribute Table
        Entity_Type_Definition: Table containing attribute information associated with the data set.
        Entity_Type_Definition_Source: USGS
      Attribute:
        Attribute_Label: FID
        Attribute_Definition: Internal feature number.
        Attribute_Definition_Source: ESRI
        Attribute_Domain_Values:
          Unrepresentable_Domain: Sequential unique whole numbers that are automatically generated.
      Attribute:
        Attribute_Label: Shape
        Attribute_Definition: Feature geometry.
        Attribute_Definition_Source: ESRI
        Attribute_Domain_Values:
          Unrepresentable_Domain: Coordinates defining the features.
      Attribute:
        Attribute_Label: FID_CMU
        Attribute_Definition: Sequential unique whole number that represents the identification number for each conceptual marsh unit.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: 1
            Range_Domain_Maximum: 46457
      Attribute:
        Attribute_Label: ATOT_M2
        Attribute_Definition: Total surface area of a marsh unit in square meters.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: 12.9601064167
            Range_Domain_Maximum: 3202425.38166
            Attribute_Units_of_Measure: square meter
      Attribute:
        Attribute_Label: AVEG_M2
        Attribute_Definition: Surface area of vegetated part of a marsh unit in square meters.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: 0.0
            Range_Domain_Maximum: 2877935.91808
            Attribute_Units_of_Measure: square meter
      Attribute:
        Attribute_Label: AMIG_M2
        Attribute_Definition: Total migration area for a marsh unit in square meters.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: 0.0
            Range_Domain_Maximum: 22123102.5416
            Attribute_Units_of_Measure: square meter
      Attribute:
        Attribute_Label: AMIGRAT
        Attribute_Definition: Ratio of the total migration area to the marsh unit area for a marsh unit.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: 0.0
            Range_Domain_Maximum: 841.04
            Attribute_Units_of_Measure: None
      Attribute:
        Attribute_Label: MIGR03
        Attribute_Definition: Migration rate for a marsh unit (in square meters per year) for a global mean sea level rise of 0.3 meters by 2100.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: 0.0
            Range_Domain_Maximum: 144273.0
            Attribute_Units_of_Measure: square meter per year
      Attribute:
        Attribute_Label: MIGR05
        Attribute_Definition: Migration rate for a marsh unit (in square meters per year) for a global mean sea level rise of 0.5 meters by 2100.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: 0.0
            Range_Domain_Maximum: 208442.0
            Attribute_Units_of_Measure: square meter per year
      Attribute:
        Attribute_Label: MIGR10
        Attribute_Definition: Migration rate for a marsh unit (in square meters per year) for a global mean sea level rise of 1.0 meters by 2100.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: 0.0
            Range_Domain_Maximum: 369281.0
            Attribute_Units_of_Measure: square meter per year
      Attribute:
        Attribute_Label: FLG
        Attribute_Definition: 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 m^2; (-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 m^2.
        Attribute_Definition_Source: USGS
        Attribute_Domain_Values:
          Range_Domain:
            Range_Domain_Minimum: -11201
            Range_Domain_Maximum: 0
            Attribute_Units_of_Measure: None
    Overview_Description:
      Entity_and_Attribute_Overview: In this dataset, marsh migration area under 2 feet of SLR are computed for each conceptual salt marsh unit in Chesapeake Bay. Additionally, the ratio of migration area to marsh unit area is calculated. Finally, migration rates (area per year) under different SLR scenarios (GMSL 0.3, 0.5 and 1.0) by 2100 are calculated. Decimal values in the attribute table are a result of double precision and they should not be taken as significant digits. Significant digits for are and migration rate are assumed to be 1 square meter and 1 square meter per year, respectively.
      Entity_and_Attribute_Detail_Citation: USGS
  Distribution_Information:
    Distributor:
      Contact_Information:
        Contact_Organization_Primary:
          Contact_Organization: U.S. Geological Survey - ScienceBase
        Contact_Address:
          Address_Type: mailing and physical address
          Address: Denver Federal Center, Building 810, Mail Stop 302
          City: Denver
          State_or_Province: CO
          Postal_Code: 80225
        Contact_Voice_Telephone: 1-888-275-8747
        Contact_Electronic_Mail_Address: sciencebase@usgs.gov
    Resource_Description: The dataset contains polygon marsh units with migration data (mu_migration_CB.shp and other shapefile components) browse graphic, and the FGDC CSDGM metadata in .xml format.
    Distribution_Liability: 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.
    Standard_Order_Process:
      Digital_Form:
        Digital_Transfer_Information:
          Format_Name: Shapefile
          Format_Version_Number: ArcGIS Pro 3.3.2
          Format_Information_Content: This zipped file contains a polygon shapefile and its components, a style layer descriptor file, metadata in xml format and a browse image.
          Transfer_Size: 220
        Digital_Transfer_Option:
          Online_Option:
            Computer_Contact_Information:
              Network_Address:
                Network_Resource_Name: https://www.sciencebase.gov/catalog/file/get/677d4d5dd34e480c9507fa29
                Network_Resource_Name: https://www.sciencebase.gov/catalog/item/677d4d5dd34e480c9507fa29
                Network_Resource_Name: https://doi.org/10.5066/P18BWN2U
            Access_Instructions: The first link in network resources is to download data directly. The second link points to a landing page with metadata and data where files can be downloaded individually. The third link is to the main landing page of the data release.
      Digital_Form:
        Digital_Transfer_Information:
          Format_Name: WMS
        Digital_Transfer_Option:
          Online_Option:
            Computer_Contact_Information:
              Network_Address:
                Network_Resource_Name: https://www.sciencebase.gov/catalogMaps/mapping/ows/677d4d5dd34e480c9507fa29?service=wms&request=getcapabilities&version=1.3.0
            Access_Instructions: The link in network resources points to the Web Mapping Services (WMS) end point.
      Digital_Form:
        Digital_Transfer_Information:
          Format_Name: WFS
        Digital_Transfer_Option:
          Online_Option:
            Computer_Contact_Information:
              Network_Address:
                Network_Resource_Name: https://www.sciencebase.gov/catalogMaps/mapping/ows/677d4d5dd34e480c9507fa29?service=wfs&request=getcapabilities&version=1.0.0
            Access_Instructions: The link in network resources points to the Web Feature Service (WFS) end point.
      Fees: None. No fees are applicable for obtaining the data set.
  Metadata_Reference_Information:
    Metadata_Date: 20250218
    Metadata_Contact:
      Contact_Information:
        Contact_Organization_Primary:
          Contact_Organization: U.S. Geological Survey
          Contact_Person: Zafer Defne
        Contact_Position: Oceanographer
        Contact_Address:
          Address_Type: mailing and physical address
          Address: 384 Woods Hole Road
          City: Woods Hole
          State_or_Province: MA
          Postal_Code: 02543
        Contact_Voice_Telephone: 508-548-8700 x2254
        Contact_Facsimile_Telephone: 508-457-2310
        Contact_Electronic_Mail_Address: 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_Name: FGDC Content Standard for Digital Geospatial Metadata
    Metadata_Standard_Version: FGDC-STD-001-1998