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:
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:
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.
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
