Metadata: Identification_Information: Citation: Citation_Information: Originator: Kate V. Ackerman Originator: Zafer Defne Originator: Neil K. Ganju Publication_Date: 20221103 Title: Elevation of marsh units in Chesapeake Bay salt marshes Edition: 1.0 Geospatial_Data_Presentation_Form: vector digital dataset (polygon) Series_Information: Series_Name: data release Issue_Identification: DOI:10.5066/P997EJYB Publication_Information: Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA Publisher: U.S. Geological Survey, Coastal and Marine Hazards and Resources Program Online_Linkage: https://doi.org/10.5066/P997EJYB Online_Linkage: https://www.sciencebase.gov/catalog/item/630f9b8bd34e36012efa0922 Larger_Work_Citation: 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: vector digital data Series_Information: Series_Name: data release Issue_Identification: DOI:10.5066/P997EJYB Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Other_Citation_Details: Suggested citation: 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. Online_Linkage: https://doi.org/10.5066/P997EJYB Online_Linkage: https://www.sciencebase.gov/catalog/item/630f73acd34e36012efa0842 Description: Abstract: This data release contains coastal wetland synthesis products for Chesapeake Bay. Metrics for resiliency, including unvegetated to vegetated ratio (UVVR), marsh elevation, and tidal range are calculated for smaller units delineated from a digital elevation model, providing the spatial variability of physical factors that influence wetland health. The U.S. Geological Survey has been expanding national assessment of coastal change hazards and forecast products to coastal wetlands 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. Purpose: The purpose of this shapefile is to calculate the mean elevation for each marsh unit and its vegetated component. Analysis of marsh elevation is part of a comprehensive assessment to identify the factors and their weights in determining the vulnerability and resiliency of salt marshes. Elevation distribution in Chesapeake Bay salt marshes is given in terms of mean elevation of conceptual marsh units. The elevation data is based primarily on the 1-meter resolution Coastal National Elevation Database (CoNED), as well as a 1.5-meter resolution NOAA DEM for North Carolina. Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2022 Currentness_Reference: publication date Status: Progress: Complete Maintenance_and_Update_Frequency: None Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -77.374707 East_Bounding_Coordinate: -75.593417 North_Bounding_Coordinate: 39.589813 South_Bounding_Coordinate: 36.374384 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: Theme_Keyword_Thesaurus: None Theme_Keyword: salt marsh Theme_Keyword: vegetation Theme_Keyword: marsh health Theme_Keyword: estuary Theme_Keyword: elevation Theme: Theme_Keyword_Thesaurus: USGS Metadata Identifier Theme_Keyword: USGS:630f9b8bd34e36012efa0922 Place: Place_Keyword_Thesaurus: None Place_Keyword: United States Place_Keyword: Chesapeake Bay Place_Keyword: Virginia Place_Keyword: Maryland Place_Keyword: North Carolina Access_Constraints: None Use_Constraints: The mean elevation 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_Person_Primary: Contact_Person: Kate Ackerman Contact_Organization: U.S. Geological Survey Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543 Country: US Contact_Voice_Telephone: 508-548-8700 x2331 Contact_Facsimile_Telephone: 508-457-2310 Contact_Electronic_Mail_Address: kackerman@usgs.gov Browse_Graphic: Browse_Graphic_File_Name: https://www.sciencebase.gov/catalog/file/get/630f9b8bd34e36012efa0922/?name=Elev_CB_Browse.png Browse_Graphic_File_Description: Graphic that shows elevation of conceptual marsh units of Chesapeake Bay salt marshes. Browse_Graphic_File_Type: PNG Native_Data_Set_Environment: Environment as of Metadata Creation: Microsoft Windows 10; Esri ArcGIS Pro (version 2.8.2) Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Marsh units and water and land boundaries inherit their horizontal accuracy from the accuracy of the source data, the conceptual marsh units, and their vertical accuracy from the elevation datasets (USGS CoNED, NOAA NC DEM). Logical_Consistency_Report: Positive elevation indicates above sea level. Marsh units with extremely low elevation (smaller than the 0.2 percentile value), extremely high elevation (larger than the 99.8 percentile value) or areas less than 900 square meters were flagged. In two areas (around marsh units 4028 and 5358), there are marsh units that have straight lines for boundaries; this is due to larger areas of hydro-flattened bathymetry/elevation values that do not allow the basin analysis to identify ridge lines between basins. Most of these marsh units have a flag that shows that the hydro-flattened area of the marsh unit is greater than 25 percent of the marsh unit area. Completeness_Report: The marsh polygons are bound to the borders of the Chesapeake Bay estuarine intertidal areas that include: 1) emergent wetlands, 2) scrub-shrub areas, 3) rooted vascular aquatic beds, 4) organic unconsolidated shores, and 5) channels of open water that are narrower than 10 meters. Sliver polygons of open salt water along the marsh edges may also be included in some instances as a result of geoprocessing (e.g., marsh unit 36608). In a few cases, linear marsh unit features that are artifacts of the NWI dataset are retained (e.g., marsh units 17309, 17310, 20453). Occasionally, marsh units are retained in this dataset even though the imagery displayed extreme change (e.g., partially or completely converted to water) from the NWI wetland delineation (e.g., marsh units 18150, 36504). In some marsh units there are small sliver gaps due to coupling of artifacts of the NWI (e.g., NWI polygons for ditches that are classified as riverine) and geoprocessing when the marsh polygons were closer than 10 meters at a specific section that is followed by a wider distance (e.g., access roads, fringing forests, etc.). The effect of these sliver gaps on the calculations is negligible (e.g., south of marsh unit 19742). In a few marsh units there are small gaps that inadvertently did not get incorporated into the marsh unit; the effect of these gaps on the calculations is negligible (e.g., marsh unit 33957). A detailed on-the-ground analysis of a single site may result in a different interpretation of the wetland and marsh unit boundaries than those established through this analysis. At Colonial National Historic Park, Virginia, palustrine emergent persistent wetlands (with freshwater tidal modifiers) were included to ensure complete coverage of the estuarine and palustrine emergent wetlands within the Park boundaries. In region CB16 (at the VA-NC border), the methodology was changed slightly to include estuarine and marine wetland polygons that are completely surrounded by salt marsh (see process step e.3). In region CB08A (Aberdeen Proving Ground, in northern Chesapeake Bay), Worldview-2 imagery was used due to the unavailability of NAIP imagery. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Horizontal accuracy for the polygon boundaries is inherited from the source layer, the conceptual marsh units, and is considered to be +/- 6 meters. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: Because the elevation values are averaged over delineated polygons, vertical accuracy depends on both the horizontal accuracy of the NWI dataset and the vertical accuracy of the source elevation datasets (primarily: USGS 1m CoNED, for NC: NOAA NC 1.5m DEM). The vertical accuracy is inherited from the source elevation datasets; it is reported to be 0.2 meters for the 1 meter CoNED dataset, and is reported as 0.06 meters for the 1.5-meter NOAA North Carolina DEM dataset. No additional accuracy assessment of the vertical accuracy has been conducted. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: Danielson, J. Originator: Tyler, D. Publication_Date: 20160501 Title: Topobathymetric Model for Chesapeake Bay Region - District of Columbia, States of Delaware, Maryland, Pennsylvania, and Virginia, 1859 to 2015 Edition: First Geospatial_Data_Presentation_Form: raster digital dataset Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Other_Citation_Details: Downloaded CoNED Digital Elevation Model geodatabase. Projection was NAD 1983 UTM Zone 18N with the North American Vertical Datum of 1988 (NAVD 88). Download date was 01/29/2020. Online_Linkage: https://topotools.cr.usgs.gov/topobathy_viewer/ Type_of_Source_Media: Digital Source_Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 18590101 Ending_Date: 20150131 Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: USGS CoNED Source_Contribution: Elevation dataset Source_Information: Source_Citation: Citation_Information: Originator: NOAA Office for Coastal Management Publication_Date: 20211130 Title: North Carolina Statewide Lidar DEM 2014 Phase 1 Geospatial_Data_Presentation_Form: raster digital data Publication_Information: Publication_Place: Charleston, SC Publisher: NOAA Other_Citation_Details: Downloaded Digital Elevation Model to be used for North Carolina. Projection was NAD 1983 UTM Zone 18N with the North American Vertical Datum of 1988 (NAVD 88). Download date was 04/04/2022. Online_Linkage: https://www.fisheries.noaa.gov/inport/item/49411 Type_of_Source_Media: Digital Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 20140406 Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: NC DEM Source_Contribution: Elevation dataset for NC Source_Information: Source_Citation: Citation_Information: Originator: NOAA National Centers for Environmental Information Publication_Date: 2019 Title: Continuously Updated Digital Elevation Model (CUDEM)-Ninth Arc-Second Resolution Bathymetric-Topographic Tiles Geospatial_Data_Presentation_Form: raster digital data Publication_Information: Publication_Place: Boulder, CO Publisher: NOAA Other_Citation_Details: Downloaded Digital Elevation Model to be used for a small part of region CB08A (Aberdeen Proving Ground) that is not covered by CoNED. Tiles downloaded: chesapeake_bay/ncei19_n39x50_w076x25_2019v1.tif, chesapeake_bay/ncei19_n39x50_w076x50_2019v1.tif. Projection was NAD 1983 UTM Zone 18N with the North American Vertical Datum of 1988 (NAVD 88). Download date was 08/20/2021. Online_Linkage: https://coast.noaa.gov/htdata/raster2/elevation/NCEI_ninth_Topobathy_2014_8483/ Type_of_Source_Media: Digital Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2019 Source_Currentness_Reference: publication date Source_Citation_Abbreviation: APG DEM Source_Contribution: Elevation dataset for Aberdeen Proving Ground Source_Information: Source_Citation: Citation_Information: Originator: Ackerman, K.V., Defne, Z., and Ganju, N.K. Publication_Date: 2022 Title: Conceptual marsh units of Chesapeake Bay salt marshes Geospatial_Data_Presentation_Form: vector digital dataset (polygon) Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Online_Linkage: https://www.sciencebase.gov/catalog/item/630f9b40d34e36012efa091d Type_of_Source_Media: Digital Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2022 Source_Currentness_Reference: publication date Source_Citation_Abbreviation: CMU_CB Source_Contribution: Used conceptual marsh units to delineate marsh unit boundaries and areas of vegetation. Process_Step: Process_Description: This process step and all subsequent process steps were performed by the same person, Kate Ackerman, in ArcGIS Pro (ver. 2.8.2), unless otherwise stated. For simple operations the name of the geoprocessing tool used is given in capital letters; for complex operations, the name of 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 (m^2) unless otherwise stated. The Chesapeake Bay was split into 16 regions to complete this analysis, refer to the accompanying image (CB_regions.png) to see the location of the regions. The methodology from region to region was consistent, however small changes were made across Chesapeake Bay; the changes are noted in the process steps below. a) Set the data frame coordinate system and projection to NAD 1983 UTM Zone 18N. b) Establish marsh unit boundaries. Dissolve the vegetated and unvegetated classes in each marsh unit to have only one class for each marsh unit. DISSOLVE(Input features=[CMU_CB.shp]; Dissolve field=FID_CMU; Statistics field=ATOT_M2 and FLG with Statistics type= First). PROJECT(Input coordinate system=WGS 1984 Web Mercator Auxiliary Sphere; Output coordinate system=NAD 1983 UTM Zone 18N) the feature dataset to obtain dissolved marsh units [mu_diss.shp]. c) Prepare elevation dataset. For the NC DEM: RESAMPLE the raster to 1m. MOSAIC TO NEW RASTER the USGS CoNED raster and the NC DEM, with the USGS CoNED taking precedence over the NC DEM. For the small areas in region CB08A (Aberdeen Proving Ground, APG) that are not covered by USGS CoNED data, the APG DEM (resampled to 1m) was used to fill in these areas. d) Create a polygon that covers the area of interest [extent.shp]. CLIP the mosaicked elevation dataset created in step (c) by [extent.shp] to create [elev_mosaic.tif]. Source_Used_Citation_Abbreviation: USGS CoNED Source_Used_Citation_Abbreviation: NC DEM Source_Used_Citation_Abbreviation: CMU_CB Process_Date: 2022 Source_Produced_Citation_Abbreviation: elev_mosaic.tif Source_Produced_Citation_Abbreviation: mu_diss.shp Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Kate Ackerman Contact_Organization: U.S. Geological Survey Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543 Country: US Contact_Voice_Telephone: 508-548-8700 x2331 Contact_Facsimile_Telephone: 508-457-2310 Contact_Electronic_Mail_Address: kackerman@usgs.gov Process_Step: Process_Description: a) Remove pixels from elevation raster that are hydro-flattened. Use FOCAL STATISTICS(Input raster=[elev_mosaic.tif], Output raster=[FocalStats_3x3_range.tif], Neighborhood settings=3x3 cell, Statistics type=range) and RASTER CALCULATOR to identify (Map algebra expression: Con("%FocalStats_3x3_range.tif%" == 0,-1,1); Output raster=[elev_mosaic_One_NegOne.tif]) and remove (Map algebra expression: SetNull("%elev_mosaic_One_NegOne.tif%", "%elev_mosaic.tif%", "value = -1"); Output raster=[elev_mosaic_noHF.tif]) all hydro-flattened areas from [elev_mosaic.tif] to create [elev_mosaic_noHF.tif]. b) Calculate the mean elevation for each marsh unit with ZONAL STATISTICS AS TABLE(Feature zone data=[mu_diss.shp], Zone field=FID_CMU; Input value raster=[elev_mosaic_noHF.tif]; Statistics type=Mean; Output table=[mu]; Ignore Nodata=True). JOIN mean elevation from [mu] table to marsh units layer [mu_diss.shp] based on the "FID_CMU" field. Export dataset as a shapefile [mu_elev.shp]. Rename "mu_MEAN" to "MU_ELEV." c) Calculate the percent of the marsh unit that has hydro-flattened area. ZONAL STATISTICS AS TABLE (Feature zone data=[mu_elev.shp], Zone field=FID_CMU; Input value raster=[elev_mosaic_One_NegOne.tif]; Statistics type=Mean; Output table=[zs_muelev_HF]; Ignore Nodata=True). ADD FIELD to the output table to calculate hydro-flattened area of each marsh unit (MU_HFAR), CALCULATE FIELD (MU_HFAR= (1-MEAN)/2). JOIN MU_HFAR field to [mu_elev.shp]. If the percent hydro-flattened area is greater than 25 percent, set the marsh unit elevation to -9999. d) Calculate the elevation of the vegetated area of the marsh unit. SELECT BY ATTRIBUTES from [CMU_CB.shp] where "TYP"= 'vegetated', output: [CMU_CB_VEG.shp]. ZONAL STATISTICS AS TABLE(Feature zone data=[CMU_CB_VEG.shp], Zone field=FID_CMU; Input value raster=[elev_mosaic_noHF.tif]; Statistics type=Mean; Output table=[vg]; Ignore Nodata=True). Join the mean elevation of the vegetated portion to [mu_elev.shp] and rename the field to "VG_ELEV." e) Calculate the percent of the vegetated portion of the marsh unit that has hydro-flattened area. ZONAL STATISTICS AS TABLE (Feature zone data=[CMU_CB_VEG.shp], Zone field=FID_CMU; Input value raster=[elev_mosaic_One_NegOne.tif]; Statistics type=Mean; Output table=[zs_muelev_HF]; Ignore Nodata=True). ADD FIELD (VG_HFAR) to output table, CALCULATE FIELD (VG_HFAR= (1-MEAN)/2). Join VG_HFAR field to [mu_elev.shp]. If the percent hydro-flattened area is greater than 25 percent, set the vegetated elevation to -9999. f) JOIN the vegetated area (AVEG_M2) from [CMU_CB_VEG.shp] to [mu_elev.shp]. Source_Used_Citation_Abbreviation: elev_mosaic.tif Process_Date: 2022 Source_Produced_Citation_Abbreviation: mu_elev.shp Process_Step: Process_Description: a) Run Python script (marsv5.py) in ArcPro (v.2.8.2) to calculate metrics that quantify the distribution of marsh unit elevation values. Skewness ("SKWNSS") is the measure of asymmetry of the elevation distribution in the vegetated part of a marsh unit. Positive skewness values, i.e. right-skewed distributions, indicate clustering of elevation distributions towards lower elevations. Negative skewness values indicate a left-skewed distribution and clustering towards higher elevations. Lower third ("LOW3RD") is the percent of elevation values that fall within the lowest third of the elevation range within the vegetated part of a marsh unit. SKWNSS and LOW3RD parameters are calculated by applying the formulation of Raposa et al. (2016) to the elevation raster within the vegetated part of each marsh unit. JOIN these values to [mu_elev.shp]. If VG_ELEV= -9999, set SKWNESS and LOW3RD values to -9999. Export to a new shapefile [mu_elev_CB.shp]. Reference: Raposa, K. B., Wasson, K., Smith, E., Crooks, J. A., Delgado, P., Fernald, S. H., et al. (2016). Assessing tidal marsh resilience to sea-level rise at broad geographic scales with multi-metric indices. Biological Conservation, 204, 263–275. https://doi.org/10.1016/J.BIOCON.2016.10.015. Source_Used_Citation_Abbreviation: mu_elev.shp Process_Date: 2022 Source_Produced_Citation_Abbreviation: mu_elev_CB.shp Process_Step: Process_Description: a) Add field "FLG" to flag anomalous marsh units based on absence of vegetation, elevation, surface area, and tidal range extrapolation. The flags are calculated in their respective shapefile (i.e., elevation flags are calculated in the elevation shapefile). Set FLG to: (-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. b) Rearrange field names and change the projection for better performance of web services with online base maps. PROJECT(Output coordinate system=WGS 1984 Web Mercator Auxiliary Sphere) the feature dataset to obtain the final elevation dataset [mu_elev_CB.shp]. Process_Date: 2022 Source_Produced_Citation_Abbreviation: mu_elev_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) Map_Projection_Parameters: False_Easting: 0.0 False_Northing: 0.0 Longitude_of_Central_Meridian: 0.0 Standard_Parallel: 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 84 Semi-major_Axis: 6378137.0 Denominator_of_Flattening_Ratio: 298.257223563 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: mu_elev_CB.shp attribute table Entity_Type_Definition: Table containing attribute information associated with the dataset. 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: Unique whole numbers used to identify each conceptual marsh unit. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 1 Range_Domain_Maximum: 46457 Attribute_Units_of_Measure: none Attribute: Attribute_Label: ATOT_M2 Attribute_Definition: Total surface area of a marsh unit. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 12.9601064176 Range_Domain_Maximum: 3202425.38056 Attribute_Units_of_Measure: m^2 Attribute: Attribute_Label: AVEG_M2 Attribute_Definition: Surface area of the vegetated part of a marsh unit. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 0.0 Range_Domain_Maximum: 2877935.91808 Attribute_Units_of_Measure: m^2 Attribute: Attribute_Label: MU_ELEV Attribute_Definition: Mean elevation of a marsh unit. If the percent hydro-flattened area is greater than 25 percent (MU_HFAR is greater than 0.25), the marsh unit elevation is set to -9999 indicating insufficient elevation data. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -3.1480701 Range_Domain_Maximum: 10.86909962 Attribute_Units_of_Measure: meters Attribute: Attribute_Label: VG_ELEV Attribute_Definition: Mean elevation of the vegetated area in a marsh unit. If there is no vegetated area in the marsh unit, the value is set to -9999. Also, if the percent hydro-flattened area in the vegetated portion is greater than 25 percent (VG_HFAR is greater than 0.25), the value is set to -9999 indicating insufficient elevation data. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -4.78264066151 Range_Domain_Maximum: 11.965080821 Attribute_Units_of_Measure: meters Attribute: Attribute_Label: MU_HFAR Attribute_Definition: Percent (in decimal form) of the marsh unit that contains hydro-flattened bathymetric/elevation values. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 0 Range_Domain_Maximum: 1 Attribute_Units_of_Measure: none Attribute: Attribute_Label: VG_HFAR Attribute_Definition: Percent (in decimal form) of the vegetated portion of the marsh unit that contains hydro-flattened bathymetric/elevation values. If there is no vegetated area in the marsh unit, the value is set to -9999. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 0 Range_Domain_Maximum: 1 Attribute_Units_of_Measure: none Attribute: Attribute_Label: SKWNSS Attribute_Definition: The measure of skewness of the elevation distribution in the vegetated part of a marsh unit. Positive skewness values (i.e., right-skewed distribution) indicate clustering of elevation distribution towards lower elevations. Negative values (left-skewed distribution) indicate clustering towards higher elevations. A value of -9999 indicates no vegetated area within the marsh unit or no elevation value for the vegetated portion. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -38.16749954 Range_Domain_Maximum: 23.9008007 Attribute_Units_of_Measure: none Attribute: Attribute_Label: LOW3RD Attribute_Definition: LOW3RD is the percent of elevation values that fall within the lowest third of the elevation range within the vegetated part of a marsh unit. Value of -9999 indicates no vegetated area within the marsh unit or no elevation value for the vegetated portion. Attribute_Definition_Source: USGS Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 0.00050712 Range_Domain_Maximum: 99.96469879 Attribute_Units_of_Measure: none 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, mean elevation for each conceptual salt marsh unit in Chesapeake Bay salt marshes has been calculated based primarily on the 1-meter resolution CoNED, and, for North Carolina, the 1.5-meter NOAA NC DEM horizontal resolution source datasets. Decimal values in the attribute table are a result of double precision calculations while significant digits are considered in defining the attribute measurement resolutions. Therefore, the smallest unit increment for area and elevation values is assumed to be 1 meter and 0.01 meter, 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: mu_elev_CB.zip (ZIP file contains the shapefile mu_elev_CB.shp and the additional shapefile components), an image of the regions used to complete the analyses (CB_regions.png), browse graphic (Elev_CB_Browse.png), and FGDC CSDGM metadata in xml format. Distribution_Liability: Although these data have been processed successfully on a computer system at 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. 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. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Not for navigational use. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: shapefile Format_Version_Number: ArcGIS Pro 2.8.2 Format_Information_Content: This dataset contains a polygon shapefile and its components and metadata in xml format. Transfer_Size: 176 Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: https://www.sciencebase.gov/catalog/file/get/630f9b8bd34e36012efa0922 Network_Resource_Name: https://www.sciencebase.gov/catalog/item/630f9b8bd34e36012efa0922 Network_Resource_Name: https://doi.org/10.5066/P997EJYB 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. The third link is to the main 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/630f9b8bd34e36012efa0922?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/630f9b8bd34e36012efa0922?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 dataset. Metadata_Reference_Information: Metadata_Date: 20221103 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Kate V. Ackerman Contact_Organization: U.S. Geological Survey Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: 384 Woods Hole Rd City: Woods Hole State_or_Province: MA Postal_Code: 02543 Country: US Contact_Voice_Telephone: 508-548-8700 x2331 Contact_Facsimile_Telephone: 508-457-2310 Contact_Electronic_Mail_Address: kackerman@usgs.gov Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998