Zafer Defne Kate V. Ackerman Brian D. Andrews Neil K. Ganju 20260526 2.0 Vector Digital Data Set (Polygon) data release DOI:10.5066/P18BWN2U Reston, Virginia U.S. Geological Survey Suggested citation: Defne, Z., Ackerman, K.V., Andrews, B.D., and Ganju, N.K., 2025, Chesapeake Bay marsh migration potential under sea-level rise (ver. 2.0, May 2026): U.S. Geological Survey data release, https://doi.org/10.5066/P18BWN2U. https://doi.org/10.5066/P18BWN2U https://www.sciencebase.gov/catalog/item/677d4d5dd34e480c9507fa29 Zafer Defne Kate V. Ackerman Brian D. Andrews Neil K. Ganju 2025 2.0 vector digital data data release DOI:10.5066/P18BWN2U Reston, VA U.S. Geological Survey Suggested citation: Defne, Z., Ackerman, K.V., Andrews, B.D., and Ganju, N.K., 2025, Chesapeake Bay marsh migration potential under sea-level rise (ver. 2.0, May 2026): U.S. Geological Survey data release, https://doi.org/10.5066/P18BWN2U. https://doi.org/10.5066/P18BWN2U https://www.sciencebase.gov/catalog/item/671a7d8ed34efed5620f910c 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 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 0.5 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: National Oceanic and Atmospheric Administration, NOAA Technical Report NOS 01, 111 pp., https://oceanservice.noaa.gov/hazards/sealevelrise/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf The purpose of this shapefile is to present the landward migration metrics for each marsh unit in Chesapeake Bay. 2025 publication date Complete None -77.3747 -75.5934 39.5898 36.3744 ISO 19115 Topic Category oceans inlandWaters environment elevation USGS Thesaurus geospatial datasets wetland ecosystems wetland functions coastal ecosystems coastal processes sea-level change sediment transport estuarine processes vegetation None salt marsh marsh health lifespan estuary Long-Term Ecological Research LTER USGS Metadata Identifier USGS:677d4d5dd34e480c9507fa29 CommonGeographicAreas Atlantic United States Maryland Virginia Chesapeake No access constraints. Please see Distribution Information for details. 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. 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. U.S. Geological Survey Zafer Defne Oceanographer mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543 508-548-8700 x2254 508-457-2310 zdefne@usgs.gov https://www.sciencebase.gov/catalog/file/get/677d4d5dd34e480c9507fa29?name=mu_migration_CB_2ft.png&allowOpen=true Total marsh migration area for each marsh unit under 2-feet of SLR in Chesapeake Bay overlaying Esri basemap. PNG Environment as of Metadata Creation: Microsoft Windows 10 Version 0.1 (Build 19042); Esri ArcGIS Pro 3.3.2 Kate V. Ackerman Zafer Defne Neil K. Ganju 2022 1.0 vector digital data data release DOI:10.5066/P997EJYB Reston, VA U.S. Geological Survey 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. Zuzak, C. 2022 NOAA Technical Report NOS 01 Silver Spring, MD National Oceanic and Atmospheric Administration https://oceanservice.noaa.gov/hazards/sealevelrise/Sea_Level_Rise_Datasets_2022.zip https://oceanservice.noaa.gov/hazards/sealevelrise/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf 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). Migration potential is zero for a marsh unit that is not connected to any migration area. 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. Horizontal accuracy is inherited from the source datasets; the marsh units, and the boundaries of marsh migration inherit from the NOAA migration raster datasets. Dataset has no vertical values. Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Office for Coastal Management (OCM) 201907 raster digital data Charleston, SC NOAA's Ocean Service, Office for Coastal Management (OCM) Download date was 10/22/2024. https://coast.noaa.gov/slr https://coast.noaa.gov/digitalcoast/data/slr-wetland.html Digital 2016 ground condition md_marshmigration_2016.zip Marsh migration inland boundary under sea-level rise Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Office for Coastal Management (OCM) 201907 raster digital data Charleston, SC NOAA's Ocean Service, Office for Coastal Management (OCM) Download date was 04/29/2024. https://coast.noaa.gov/slr https://coast.noaa.gov/digitalcoast/data/slr-wetland.html Digital 2016 ground condition va_marshmigration_2016.zip Marsh migration inland boundary under sea-level rise Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Office for Coastal Management (OCM) 201907 raster digital data Charleston, SC NOAA's Ocean Service, Office for Coastal Management (OCM) Download date was 06/04/2024. https://coast.noaa.gov/slr https://coast.noaa.gov/digitalcoast/data/slr-wetland.html Digital 2016 ground condition nc_marshmigration_2016.zip Marsh migration inland boundary under sea-level rise 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. Zuzak, C. 2022 NOAA Technical Report NOS 01 Silver Spring, MD National Oceanic and Atmospheric Administration https://oceanservice.noaa.gov/hazards/sealevelrise/Sea_Level_Rise_Datasets_2022.zip https://oceanservice.noaa.gov/hazards/sealevelrise/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf Digital 2022 ground condition SLR data Sea-level rise projections for 2100 for selected scenarios Kate Ackerman Zafer Defne Neil Kamal Ganju 2022 vector digital data data release DOI:10.5066/P997EJYB Reston, VA U.S. Geological Survey https://doi.org/10.5066/p997ejyb https://www.sciencebase.gov/catalog/item/630f9ba4d34e36012efa0924 Digital 2022 publication date mu_UVVR_CB.shp Marsh unit outlines U.S. Geological Survey 20220324 vector digital data Reston, Virginia U.S. Geological Survey Download date was 09/26/2025. https://www.usgs.gov/core-science-systems/ngp/national-hydrography Digital 20220324 publication date NHDPlusCatchment NHD Plus Catchment polygons U.S. Fish and Wildlife Service 20191001 vector digital dataset (polygon) Madison, WI U.S. Fish and Wildlife Service Downloaded wetlands data for Virginia, Maryland and North Carolina in shapefile format from the NWI download page. Projection was NAD 1983 Albers. Download date was 01/02/2020. https://www.fws.gov/wetlands/data/Data-Download.html Digital 2019 publication date NWI Wetland classification 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 into a single feature dataset [mm_MD_VA_NC_merge_UTM18_2011.shp]. md_marshmigration_2016.zip va_marshmigration_2016.zip nc_marshmigration_2016.zip 2024 mm_MD_VA_NC_merge_UTM18_2011.shp U.S. Geological Survey Zafer Defne Oceanographer mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543 508-548-8700 x2254 508-457-2310 zdefne@usgs.gov 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 the open water mask. Download NWI layers for VA, MD and NC, then project to the same coordinate system with the rest of the input data and merge. SELECT("ATTRIBUTE" LIKE 'E1%') and export as [E1_CB.shp]. j) Prepare and split the union of catchments to immediate catchments and remote catchments so that the remote catchments can be merged by proximity. Specifically, to prepare, ERASE the open water mask and 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]. k) 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]. l) 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]. mm_MD_VA_NC_merge_UTM18_2011.shp mu_UVVR_CB.shp NHDPlusCatchment 2024 marsh_migration_polygons.shp 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 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. 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: National Oceanic and Atmospheric Administration, NOAA Technical Report NOS 01, 111 pp., https://oceanservice.noaa.gov/hazards/sealevelrise/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf 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). 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, project to Web Mercator projection, and export features as mu_migration_CB.shp. marsh_migration_polygons.shp mu_UVVR_CB.shp 2024 mu_migration_CB.shp This is the revision step for Version 2.0. Only keep the GMSL rise scenario closest to 2 feet (0.5 meters rise by year 2100). Download the original dataset [mu_migration_CB.shp], remove fields MIGR03, MIGR10 and keep MIGR05. Add the previously missing documentation of processing step of erasing open water using National Wetlands Inventory's E1 attribute. Although performed, this step was omitted from the metadata in version 1 of this dataset. Update the Abstract, Lineage and Entity and Attribute Information components to reflect this change. Export data and metadata after appending "_2ft" to all names to differentiate between different cases. mu_migration_CB.shp 2026 mu_migration_CB_2ft.shp Vector G-polygon 46457 WGS 1984 Web Mercator Auxiliary Sphere (ESRI Full Name: WGS_1984_Web_Mercator_Auxiliary_Sphere) 0.0 0.0 0.0 0.0 coordinate pair 0.6096 0.6096 meters D_WGS_1984 WGS_1984 6378137.0 298.257223563 mu_migration_CB_2ft.shp Attribute Table Table containing attribute information associated with the data set. USGS FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. FID_CMU Sequential unique whole number that represents the identification number for each conceptual marsh unit. USGS 1 46457 ATOT_M2 Total surface area of a marsh unit in square meters. USGS 12.9601064167 3202425.38166 square meter AVEG_M2 Surface area of vegetated part of a marsh unit in square meters. USGS 0.0 2877935.91808 square meter AMIG_M2 Total migration area for a marsh unit in square meters. USGS 0.0 22123102.5416 square meter AMIGRAT Ratio of the total migration area to the marsh unit area for a marsh unit. USGS 0.0 841.04 None MIGR05 Migration rate for a marsh unit (in square meters per year) for a global mean sea level rise of 0.5 meters by 2100. USGS 0.0 208442.0 square meter per year 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 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. USGS -11201 0 None 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 the SLR scenario closest to 2 feet (GMSL 0.5 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. USGS U.S. Geological Survey - ScienceBase mailing and physical address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 1-888-275-8747 sciencebase@usgs.gov The dataset contains polygon marsh units with migration data (mu_migration_CB_2ft.shp and other shapefile components) browse graphic, and the FGDC CSDGM metadata in .xml format. 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. Shapefile ArcGIS Pro 3.3.2 This zipped file contains a polygon shapefile and its components, metadata in xml format and a browse image. 220 https://www.sciencebase.gov/catalog/file/get/677d4d5dd34e480c9507fa29 https://www.sciencebase.gov/catalog/item/677d4d5dd34e480c9507fa29 https://doi.org/10.5066/P18BWN2U 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. None. No fees are applicable for obtaining the data set. 20260526 U.S. Geological Survey Zafer Defne Oceanographer mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543 508-548-8700 x2254 508-457-2310 whsc_data_contact@usgs.gov The metadata contact email address is a generic address in the event the person is no longer with USGS. FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998