Conceptual marsh units of salt marshes on the Eastern Shore of Virginia

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Metadata:

Identification_Information:
Citation:
Citation_Information:
Originator: Kate V. Ackerman
Originator: Zafer Defne
Originator: Neil K. Ganju
Publication_Date: 20230328
Title:
Conceptual marsh units of salt marshes on the Eastern Shore of Virginia
Edition: 1.0
Geospatial_Data_Presentation_Form: vector digital dataset (polygon)
Series_Information:
Series_Name: data release
Issue_Identification: DOI:10.5066/P9E6V0QK
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/P9E6V0QK
Online_Linkage: Larger_Work_Citation:
Citation_Information:
Originator: Kate V. Ackerman
Originator: Zafer Defne
Originator: Neil K. Ganju
Publication_Date: 2023
Title:
Geospatial characterization of salt marshes on the Eastern Shore of Virginia
Edition: 1.0
Geospatial_Data_Presentation_Form: vector digital data
Series_Information:
Series_Name: data release
Issue_Identification: DOI:10.5066/P9E6V0QK
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., 2023, Geospatial characterization of salt marshes on the Eastern Shore of Virginia: U.S. Geological Survey data release, https://doi.org/10.5066/P9E6V0QK.
Online_Linkage: https://doi.org/10.5066/P9E6V0QK
Online_Linkage:
Description:
Abstract:
This data release contains coastal wetland synthesis products for the Atlantic-facing Eastern Shore of Virginia (the data release for the Chesapeake Bay-facing portion of the Eastern Shore of Virginia is found here: https://doi.org/10.5066/P997EJYB). 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:
These polygons were created to be used in evaluating the spatial variation of the response and resiliency of salt marsh complexes based on consistently defined marsh units while facilitating a better understanding of the relative importance of the processes involved. The salt marshes of the Eastern Shore of Virginia were delineated to smaller, conceptual marsh units by the geoprocessing of surface elevation data. Flow accumulation based on the relative elevation of each location is used to determine the ridge lines that separate each marsh unit while the surface slope is used to automatically assign each unit a drainage point where water is expected to drain through.
Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2023
Currentness_Reference: Publication date
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -75.977747
East_Bounding_Coordinate: -75.474028
North_Bounding_Coordinate: 37.881830
South_Bounding_Coordinate: 37.085411
Keywords:
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: oceans
Theme_Keyword: inlandWaters
Theme_Keyword: environment
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: vegetation
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: salt marsh
Theme_Keyword: marsh health
Theme_Keyword: estuary
Theme:
Theme_Keyword_Thesaurus: USGS Metadata Identifier
Theme_Keyword: USGS:63e53a36d34efa0476ade047
Place:
Place_Keyword_Thesaurus: None
Place_Keyword: United States
Place_Keyword: Atlantic Ocean
Place_Keyword: Virginia
Place_Keyword: Wallops Island
Place_Keyword: Chincoteague National Wildlife Refuge
Place_Keyword: Metompkin Island
Place_Keyword: Cedar Island
Place_Keyword: Parramore Island
Place_Keyword: Hog Island
Place_Keyword: Mockhorn Island
Place_Keyword: Smith Island
Place_Keyword: Fisherman Island National Wildlife Refuge
Place_Keyword: Eastern Shore National Wildlife Refuge
Place_Keyword: Virginia Coast Reserve
Access_Constraints: None
Use_Constraints:
These polygons are 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 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
Browse_Graphic:
Browse_Graphic_File_Name: Browse_Graphic_File_Description:
Graphic that shows the conceptual marsh units of salt marshes on the Eastern Shore of Virginia.
Browse_Graphic_File_Type: PNG
Native_Data_Set_Environment:
Environment as of Metadata Creation: Microsoft Windows 10; Esri ArcGIS Pro (version 2.8.8)
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
Marsh units and water and land boundaries inherit their accuracy from the U.S. Fish and Wildlife Service National Wetland Inventory (USFWS NWI). However, the lineage of the source data indicates that the underlying data span multiple years and the mapped features may have changed since the date of imagery. Accuracy of marsh unit delineation depends on the vertical and horizontal accuracy of the elevation data (2015 USGS Lidar DEM). Accuracy of the vegetated and unvegetated polygons is based on the National Agriculture Imagery Program (NAIP) products from 2018 (0.6-meter resolution). Any vegetated or unvegetated polygons less than 9 square meters (m^2) were merged with the surrounding majority class unless they are at the edge of a marsh unit. When creating marsh units, conterminous polygons smaller than 900 m^2 were merged with the larger polygon of the same type.
Logical_Consistency_Report:
Topological errors that occurred during geoprocessing were automatically removed by the topological rules used for the analysis. The polygons were checked for correct geometry and do not overlap. Small polygons (less than 9 m^2) were assumed to be marginal and were assigned the classification from the surrounding majority value.
Completeness_Report:
The marsh polygons are bound to the borders of the Eastern Shore of Virginia's 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. 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 638, 796, 1366). In a few areas, there are no marsh units where there is visible marsh plain (e.g., west of marsh units 4583 and 4566; west of 5878; south of 5910; west of 5855), because the areas are classified in the NWI as estuarine intertidal unconsolidated shore, which is not included in our salt marsh boundaries. In a few locations, there may be areas that that are classified as unvegetated but are in fact very sparsely vegetated. 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.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Horizontal accuracy is inherited from the digital elevation model (2015 USGS Lidar DEM). Vegetated and unvegetated polygons were based on the 0.6-meter resolution NAIP imagery. Although the analyses were performed at 1-meter resolution, the horizontal accuracy is superseded by NAIP imagery accuracy which is +/-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 dataset (1-meter 2015 USGS Lidar DEM). The vertical accuracy is inherited from the source elevation dataset; it is reported to be 0.06 meters. No additional accuracy assessment of the vertical accuracy has been conducted.
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: 2018
Title: 2015 USGS Lidar DEM: Eastern Shore VA
Edition: First
Geospatial_Data_Presentation_Form: raster digital dataset
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Other_Citation_Details:
Downloaded 1-meter 2015 USGS Lidar DEM. Projection was NAD 1983 UTM Zone 18N with the North American Vertical Datum of 1988 (NAVD 88). Download date was 04/13/2021.
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/51444
Type_of_Source_Media: Digital
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20150411
Ending_Date: 20150424
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: USGS DEM
Source_Contribution: Elevation dataset
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Department of Agriculture
Publication_Date: 2018
Title: NAIP Digital Ortho Photo Image
Geospatial_Data_Presentation_Form: remote-sensing image
Publication_Information:
Publication_Place: Salt Lake City, Utah
Publisher: USDA-FSA-APFO Aerial Photography Field Office
Other_Citation_Details:
Downloaded NAIP 4-band, 0.6-meter resolution imagery from the USGS Earth Explorer. Projection was NAD 1983 UTM Zone 18N. Download date was 01/17/2020.
Online_Linkage: https://earthexplorer.usgs.gov
Type_of_Source_Media: Digital
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2018
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: NAIP
Source_Contribution: Aerial imagery dataset
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Fish and Wildlife Service
Publication_Date: 20191001
Title: National Wetland Inventory
Geospatial_Data_Presentation_Form: vector digital dataset (polygon)
Publication_Information:
Publication_Place: Madison, WI
Publisher: U.S. Fish and Wildlife Service
Other_Citation_Details:
Downloaded wetlands data for Virginia in shapefile format from the NWI download page. Projection was NAD 1983 Albers. Download date was 01/02/2020.
Online_Linkage: https://www.fws.gov/wetlands/data/Data-Download.html
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: NWI
Source_Contribution: Wetlands dataset
Process_Step:
Process_Description:
This process step and all subsequent process steps were performed by the same person, Kate Ackerman, in ArcGIS Pro (ver. 2.8.8), 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.
a) Set the data frame coordinate system and projection to NAD 1983 UTM Zone 18N.
b) Prepare elevation dataset. Combine all downloaded tiles into one raster, using MOSAIC TO NEW RASTER, and PROJECT RASTER to NAD 1983 UTM Zone 18N.
c) Create a polygon that covers the area of interest [extent.shp]. CLIP the mosaicked elevation dataset created in step (b) by [extent.shp] to create [elev_mosaic.tif].
Source_Used_Citation_Abbreviation: USGS DEM
Process_Date: 2022
Source_Produced_Citation_Abbreviation: elev_mosaic.tif
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:
This process step creates two mask polygons to define analysis boundaries over the area of interest. In order to account for the possible influence of the surrounding terrain on the analysis, a mask area larger than the salt marsh extent is created [UVVR_mask.shp]. This larger mask area is clipped to the boundaries of the salt marsh area to create [MU_mask.shp]. This process step explains how [UVVR_mask.shp] and [MU_mask.shp] are created and edited to determine which interior polygons are removed.
a) Create a shapefile of the salt marshes as defined by NWI. EXPORT features (use the same coordinate system as the data frame) from NWI dataset of all wetlands for the area (referred to here as [NWI_entire.shp]) after SELECT (ATTRIBUTE LIKE 'E2%EM%' OR ATTRIBUTE LIKE 'E2AB3%' OR ATTRIBUTE LIKE 'E2EM%' OR ATTRIBUTE LIKE 'E2SS%' OR ATTRIBUTE LIKE 'E2US4%') to select from estuarine intertidal areas of 1) emergent wetland, 2) scrub-shrub area, 3) rooted vascular aquatic bed, 4) organic unconsolidated shore classes to create [NWI_exclusive_select.shp].
b) Create the preliminary masks that will be edited in the subsequent steps to make the final masks. BUFFER salt marsh classes (Input features=[NWI_exclusive_select.shp]; Linear unit=5 meters; Dissolve type=All) to obtain the mask polygon [buff5m.shp] and ELIMINATE POLYGON PART (Input features= [buff5m.shp]; Condition=Percentage; Percentage=99; Eliminate contained part only) to remove small interior polygons to obtain [UVVR_mask01.shp]. Apply BUFFER (Input features=[UVVR_mask01.shp]; Linear unit= -5 meters; Dissolve type= All) to obtain [MU_mask01.shp].
c) EXPORT features from NWI dataset after SELECT (ATTRIBUTE NOT LIKE 'E%' OR ATTRIBUTE LIKE '%FO') to obtain features that are not estuarine or are forested estuarine [NWI_inclusive_select.shp]. MULTIPART TO SINGLEPART to separate individual polygons [NWI_inclusive_single.shp].
d) To exclude the voids in the NWI map during the analysis, these interior polygons need to be removed from the mask. ERASE [NWI_exclusive_select.shp] from [extent.shp] and MULTIPART TO SINGLEPART to get [NWI_exc_voids_single.shp].
To create the final mask shapefiles ([MU_mask.shp] and [UVVR_mask.shp]), areas that should not be included are removed (e.g., forest areas), and areas that should be included are incorporated (estuarine and marine wetland systems that are completely surrounded by salt marsh (e.g., interior ponds)):
e)SELECT BY LOCATION from [NWI_inclusive_single.shp] that are completely within the [MU_mask01.shp] and SELECT BY LOCATION from [NWI_exc_voids_single.shp] that are completely within the [MU_mask01.shp]. UNION all feature sets to get polygons to be excluded [erase_inside.shp] from the final masks.
f) Spatially join the [NWI_entire.shp] to [erase_inside.shp] in order to assign wetland attributes to the [erase_inside.shp] polygons. SPATIAL JOIN (target features= [erase_inside.shp]; join features= [NWI_entire.shp]; output feature class= [erase_inside_NWI_info.shp]; join operation= one to one; keep all target features; match option= intersect; search radius= -1 m).
g) Select the polygons that are marine or non-forested estuarine wetlands from [erase_inside_NWI_info.shp]: SELECT (ATTRIBUTE LIKE 'E1%' OR ATTRIBUTE LIKE 'E2AB%' OR ATTRIBUTE LIKE 'E2RF%' OR ATTRIBUTE LIKE 'E2SB%' OR ATTRIBUTE LIKE 'E2RS%' OR ATTRIBUTE LIKE 'E2US%' OR ATTRIBUTE LIKE 'E2EM%' OR ATTRIBUTE LIKE ‘E2SS%’ OR ATTRIBUTE LIKE ‘M1%’ OR ATTRIBUTE LIKE ‘M2%) to select all marine systems, estuarine subtidal systems, estuarine intertidal areas of aquatic bed, reef, streambed, rocky shore, unconsolidated shore, emergent or scrub-shrub [erase_inside_keepIntPonds.shp].
h) Remove the polygons from [erase_inside_NWI_info.shp] that should be retained (these are the interior ponds): ERASE (input feature= [erase_inside_NWI_info.shp]; erase feature= [erase_inside_keepIntPonds.shp]; output feature= [erase_inside_final.shp]).
i) If any additional polygons need to be removed from the mask, include them in a new feature layer [erase_mask_manual.shp] and MERGE with [erase_inside_final.shp].
j) Remove any unwanted polygons from the original [MU_mask01.shp] to make the final [MU_Mask.shp]: ERASE (input feature= [MU_mask01.shp]; erase feature= [erase_inside_final.shp]; output feature= [MU_mask.shp]).
k) BUFFER [MU_mask.shp] by 5m (side type= full; end type= round; method: geodesic; dissolve type: single feature) to obtain [UVVR_mask.shp].
Source_Used_Citation_Abbreviation: NWI
Process_Date: 2022
Source_Produced_Citation_Abbreviation: MU_mask.shp
Source_Produced_Citation_Abbreviation: UVVR_mask.shp
Process_Step:
Process_Description:
Define preliminary boundaries for marsh units by basin analysis:
a) EXTRACT BY MASK from elevation dataset [elev_mosaic.tif] using [UVVR_mask.shp] polygon.
b) FILL (no Z limit) sinks in extracted elevation raster.
c) Calculate FLOW DIRECTION (do not force edge cells to flow outward) raster.
d) Calculate BASIN based on flow direction raster [basin_buff5m.tif].
e) Apply MAJORITY FILTER (Number of neighbors=8) to clean the raster [basin_buff5m.tif] and convert RASTER TO POLYGON [basin_b5m_poly.shp]. Create a 1-meter buffered marsh units mask [MU_mask_buff1m.shp] and use this to CLIP the polygon to create [basin_b5m_polyclip.shp]. This additional buffer is necessary to prevent any polygon smoothing algorithm from changing the exterior boundaries and will be removed by clipping to the [MU_mask.shp] later. Using [basin_b5m_polyclip.shp] as the input, MULTIPART TO SINGLEPART and ADD GEOMETRY ATTRIBUTES(Geometry properties=Area_geodesic; Area unit=Square_meters) to get [basin_single.shp].
Source_Used_Citation_Abbreviation: elev_mosaic.tif
Process_Date: 2022
Source_Produced_Citation_Abbreviation: basin_single.shp
Process_Step:
Process_Description:
This step merges the "orphan marsh units," units that are smaller than 5000 m^2, to the nearest to "parent marsh units," units that are larger than 5000 m^2, to obtain the preliminary marsh units. A Python script that iteratively calls a list of ArcGIS tools to aggregate orphan units on parent units is used.
a) Create orphan marsh unit features by exporting marsh units from [basin_single.shp] with an area less than 5000 m^2 [inputfeatures.shp].
b) Create parent marsh unit features by exporting marsh units with an area greater than or equal to 5000 m^2 [nearfeatures.shp].
c) Run Python script (hydUnitloop.py). At each iteration step, the script uses NEAR tool to find orphan marsh units within 1 meter of a parent marsh unit and merges them to the parent using UNION and DISSOLVE tools. The orphan units merged with a parent unit are removed from the orphan units dataset. The script will iterate until there is no change in the number of parent or orphan marsh units. The remaining orphan marsh units are those that are more than 1 meter away from any parent. DISSOLVE them to create larger orphan units by grouping the orphans attached together into larger units. MULTIPART TO SINGLEPART to have single part polygons with unique identifiers. UNION(with gaps) single part features with parent units to obtain preliminary marsh units [pMUopt1.shp]. SMOOTH POLYGON(Smoothing algorithm=PAEK; Smoothing tolerance=15 meters) to get the smoothed marsh units polygon [pMUopt1_smooth.shp].
d) CLIP the extra buffer around the smoothed marsh units using the marsh units mask [MU_mask.shp]. If this results in any additional marsh units with an area less than 5000 m^2, dissolve into the nearest parent units repeating the same steps above to obtain [pMUopt1_clip_final.shp].
e) Compute the final marsh units by removing any artifacts from [pMuOpt1_clip_final.shp] using ELIMINATE and REPAIR GEOMETRY tools. ELIMINATE(Expression="Area_geo" less than 900; Eliminating by border) polygon slivers smaller than 900 m^2 by merging them to the main polygon. MULTIPART TO SINGLEPART to get conceptual marsh units [CMU.shp]. This only applies to polygons that are bordering other polygons. Polygons that are not bordering other polygons are not affected as those are more likely to be real features as opposed to geoprocessing artifacts. To [CMU.shp], ADD FIELD “FID_CMU” and CALCULATE FIELD as FID_CMU= FID x 1. Delete fields from [CMU.shp] so that only area_geo and FID_CMU remain. REPAIR GEOMETRY of [CMU.shp].
f) DISSOLVE the conceptual marsh units to get the final outlines for the marsh complex [CMU_mask_final.shp].
Source_Used_Citation_Abbreviation: basin_single.shp
Process_Date: 2022
Source_Produced_Citation_Abbreviation: CMU_mask_final.shp
Process_Step:
Process_Description:
Determine the vegetated and unvegetated areas by image processing.
a) MOSAIC TO NEW RASTER the NAIP tiles.
b) EXTRACT BY MASK from the elevation raster [elev_mosaic.tif] and the NAIP imagery raster using [UVVR_mask.shp] polygon and append “UVVR_mask” to the file name. Rescale the elevation raster values to the same range with 8-bit NAIP imagery (0 to 255) using min-max scaling in RASTER CALCULATOR (map algebra expression: (("elev_mosaic_UVVR_mask.tif"-(min value of the input raster))*(255-0)/(max value of the input raster)-( min value of the input raster)))+0). Perform ISO CLUSTER UNSUPERVISED CLASSIFICATION with 5 input bands: the Near Infrared, Blue, Green, and Red from the NAIP imagery and the rescaled elevation raster; with 32 classes and a minimum class size of 5000 cells. RECLASSIFY the classified raster by visually comparing the NAIP imagery to obtain the unvegetated-vegetated raster [UVVc.tif]. In some regions, a couple of the 32 classes are classified as vegetated in one area but unvegetated in another area. For these classes, the area can be split into separate sections to allow one section to be classified as vegetated and the other as unvegetated.
c) Dissolve unvegetated regions smaller than a threshold value to the surrounding vegetated regions and vice versa to clean the UVV raster. For this purpose, use the REGION GROUP(Number of neighbors=4; Zone grouping method=Within; Add Link field to output) to get the [UVV_region.tif], and TEST("Count" < 9) to set a threshold value of 9 raster cells [lt9.tif]. Use RASTER CALCULATOR to toggle the value of the Link field in the region raster [Map algebra expression=Con("%lt9.tif%", ~Lookup("%UVVc_region.tif%","LINK"),Lookup("%UVVc_region.tif%","LINK"))], where the test raster indicates regions with areas smaller than the threshold.
d) RASTER TO POLYGON(Simplify polygons=False) and CLIP with the final marsh complex outline [CMU_mask_final.shp] to obtain [UVVc_filt_clip.shp].
e) REPAIR GEOMETRY, ADD GEOMETRY ATTRIBUTES(Geometry properties=Area_geodesic; Area unit=Square_meters), CALCULATE FIELD(Python_9.3 expression; Field name=gridcode, Expression=filt(!gridcode!, !AREA_GEO!), Code Block= def filt(gridcode, AREA_GEO):/if gridcode== 0 and AREA_GEO < 9:/return 1/else:/return gridcode) and DISSOLVE(Create multipart features=False) to get filtered, clipped and dissolved unvegetated-vegetated polygons [UVVc_filt_clip_diss.shp].
f) INTERSECT the final conceptual marsh units [CMU.shp] with unvegetated-vegetated polygons [UVVc_filt_clip_diss.shp], REPAIR GEOMETRY, and calculate the area of unvegetated and vegetated polygons in each marsh unit. To do this ADD GEOMETRY ATTRIBUTES (Geometry properties=Area_geodesic; Area unit=Square_meters) to get [UVV_poly.shp], and DISSOLVE(Input features=[UVV_poly.shp]; Dissolve fields=FID_CMU, gridcode; Statistics field=gridcode.MEAN) and REPAIR GEOMETRY to get [UVV_poly_diss.shp]. Add fields "TYP", "APGN_M2", and "ATOT_M2" for type of polygon indicating vegetated or unvegetated, surface area of the polygon, and total surface area of the marsh unit, respectively, and calculate "APGN_M2" and "ATOT_M2" areas.
g) Visually inspect and manually remove marsh units that are fully forested due to polygon artifacts that are a result of buffering. Remove marsh units that are completely unvegetated, unattached to other marsh units (i.e., islands) and less than 25,000 m2, as these are artifacts of the NWI dataset. Remove marsh units that are linear features (edges parallel to each other) and unattached to other marsh units (i.e., islands), as these are artifacts of the NWI dataset.
Source_Used_Citation_Abbreviation: NAIP
Source_Used_Citation_Abbreviation: elev_mosaic.tif
Process_Date: 2022
Source_Produced_Citation_Abbreviation: UVV_poly_diss.shp
Process_Step:
Process_Description:
Finalize the conceptual marsh units.
a) Add field "COLORID" to cycle through integers from 0 to 9 to be used for coloring the marsh units. This field is used for display purposes only to distinguish between marsh units.
b) 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.
c) 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 conceptual marsh units [CMU_ESV].
Source_Used_Citation_Abbreviation: UVV_poly_diss.shp
Process_Date: 2022
Source_Produced_Citation_Abbreviation: CMU_ESV.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: 12586
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: CMU_ESV attribute table
Entity_Type_Definition:
Table containing attribute information associated with the dataset.
Entity_Type_Definition_Source: Producer Defined
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. These numbers are duplicated when a marsh unit has both vegetated and unvegetated sub-polygons.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0
Range_Domain_Maximum: 6357
Attribute_Units_of_Measure: none
Attribute:
Attribute_Label: APGN_M2
Attribute_Definition:
Surface area of the selected polygon type (vegetated or unvegetated).
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.0105473279244
Range_Domain_Maximum: 1628088.8009
Attribute_Units_of_Measure: m^2
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: 123.826608084
Range_Domain_Maximum: 1906442.13071
Attribute_Units_of_Measure: m^2
Attribute:
Attribute_Label: TYP
Attribute_Definition:
Classification of the polygon features in a marsh unit as vegetated or unvegetated.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: unvegetated
Enumerated_Domain_Value_Definition: Unvegetated part of the marsh unit.
Enumerated_Domain_Value_Definition_Source: USGS
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: vegetated
Enumerated_Domain_Value_Definition: Vegetated part of the marsh unit.
Enumerated_Domain_Value_Definition_Source: USGS
Attribute:
Attribute_Label: COLORID
Attribute_Definition:
Recycling sequential whole numbers (0-9) that are used for display purposes when plotting conceptual marsh units. These numbers are duplicated when a marsh unit has both vegetated and unvegetated sub-polygons.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0
Range_Domain_Maximum: 9
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: -11100
Range_Domain_Maximum: 0
Overview_Description:
Entity_and_Attribute_Overview:
In this dataset, the salt marsh complexes across the Atlantic-facing Eastern Shore of Virginia have been delineated to conceptual salt marsh units to facilitate unit by unit evaluation of the response and resiliency of the marsh system to physical and biogeochemical drivers. Each unit is also analyzed based on the vegetated and unvegetated surface area coverage, the ratio of which can be an independent measure of the marsh health of salt marshes on the Atlantic and Pacific coasts of the United States. 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 values is assumed to be 1 meter.
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_ESV.zip (ZIP file contains the shapefile mu_elev_ESV.shp and the additional shapefile components), browse graphic (Elev_ESV_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 2.8.8
Format_Information_Content:
This dataset contains a polygon shapefile and its components and metadata in xml format.
Transfer_Size: 412
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information: 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: 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: 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: 20230329
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: 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: Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998

This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P9E6V0QK/CMU_ESV.html>
Generated by mp version 2.9.51 on Wed Mar 29 13:42:27 2023