Attribute_Accuracy_Report:
Marsh units and water and land boundaries inherit their accuracy from the 2017 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 1-meter resolution U.S. Geological Survey Coastal National Elevation Database (USGS CoNED) data from 2016. Accuracy of the vegetated and unvegetated polygons is based on the 1-meter resolution National Agriculture Imagery Program (NAIP) products from 2017. Any vegetated or unvegetated polygons less than 9 square meters (m^2) were merged with the surrounding majority class. When creating marsh units, conterminous polygons smaller than 900 m^2 were merged with the larger polygon of the same type. Since small marsh islands are common in Hudson Valley and New York City, many polygons in this dataset could not be merged with larger units.
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. This resulted in polygons that were removed from the dataset and FID CMU values that are not sequential. A visual comparison between NAIP imagery was performed at randomly selected sites to verify the land and water boundaries.
The marsh polygons are bound to the borders of the Hudson Valley and New York City 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. 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.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Horizontal accuracy is inherited from CoNED Digital Elevation Models. Vegetated and unvegetated polygons were based on the 1-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 data, CoNED. CoNED vertical elevation accuracy was 0.2 meters.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: 2016
Title: Coastal National Elevation Database
Geospatial_Data_Presentation_Form: Raster Digital dataset
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Online_Linkage: https://nationalmap.gov/viewer.html
Type_of_Source_Media: Digital
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2016
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: CoNED
Source_Contribution:
Downloaded CoNED Digital Elevation Model from the National Map. Projection was NAD 1983 UTM Zone 18N with the North American Vertical Datum of 1988 (NAVD 88). Download date was 2020/03/01.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: 2017
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
Online_Linkage: https://earthexplorer.usgs.gov
Online_Linkage:
Type_of_Source_Media: Digital
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2017
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: NAIP
Source_Contribution:
Downloaded NAIP 1-meter resolution imagery from the USGS Earth Explorer. Projection was WGS 1984 Web Mercator Auxiliary Sphere. Download date was 2019/08/01.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Fish and Wildlife Service
Publication_Date: 2017
Title: National Wetland Inventory New York Wetlands
Geospatial_Data_Presentation_Form: Vector Digital dataset (Polygon)
Publication_Information:
Publication_Place: Madison, WI
Publisher: U.S. Fish and Wildlife Service
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: 2017
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: NWI
Source_Contribution:
Downloaded wetlands data for the state of New York in shapefile format from the NWI download page. Projection was NAD 1983 Albers. Download date was 2019/08/01.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
New England Interstate Water Pollution Control Commission prepared by Cameron Engineering and Associates, LLP
Publication_Date: 2015
Title: Long Island Tidal Wetlands Trends Analysis
Geospatial_Data_Presentation_Form: Vector Digital Data Set (Polygon)
Online_Linkage: http://www.dec.ny.gov/lands/5113.html
Type_of_Source_Media: Digital
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2015
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: NYSDEC
Source_Contribution:
Wetland polygon shapefile prepared for Long Island Tidal Wetlands Trends Analysis. Data available by request. Data acquired 2019/05/01.
Process_Step:
Process_Description:
This process step and all subsequent process steps were performed by the same person, Robert Welk, in ArcMap (ver. 10.7.1) using tools from ArcToolbox, 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 (m^2) unless otherwise stated.
Set the data frame coordinate system and projection to NAD 1983 UTM Zone 18N. Prepare elevation dataset to be clipped to the boundaries polygon. MOSAIC TO NEW RASTER(Pixel type= 32 bit float; Mosaic operator=Mean; Cellsize=1 m) the entire CoNED raster to a new raster dataset with 1 meter resolution [elev_mosaic.tif].
Source_Used_Citation_Abbreviation: CoNED
Process_Date: 2020
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey, Northeast Region
Contact_Person: Robert J Welk
Contact_Position: Hydrologic Technician
Contact_Address:
Address_Type: mailing address
Address: 2045 Route 112
City: Coram
State_or_Province: NY
Postal_Code: 11727
Country: US
Contact_Voice_Telephone: 631-736-0783 x141
Contact_Electronic_Mail_Address: rwelk@usgs.gov
Process_Step:
Process_Description:
Prepare mask polygon to define analysis boundaries. 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 first created [UVVR_mask]. At the end of the analysis the results are clipped to the boundaries of the salt marsh area [MU_mask]. Both UVVR_mask and MU_mask are edited to determine which interior polygons are removed.
a) MERGE NWI wetland polygons with NYSDEC wetland polygons to obtain [NWI_DEC.shp].
b) EXPORT features from NWI_DEC.shp dataset 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 [NWI_exclusive_select.shp].
c) BUFFER(Input features=[NWI_exclusive_select.shp]; Linear unit=5 meters; Dissolve type=All) to obtain the mask polygon [buff5m.shp] and ELIMINATE POLYGON PART(Condition=Percentage; Percentage=99; Eliminate contained part only) to obtain [UVVR_mask01.shp]. Apply buffer with -5 meters to obtain [MU_mask01.shp].
d) 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. MULTIPART TO SINGLEPART to separate individual polygons [NWI_inclusive_single.shp].
e) To exclude the voids in the NWI map during the analysis, these interior polygons need to be removed from the mask. Create a rectangular polygon that covers the domain [extent.shp]. ERASE [NWI_excusive_select.shp] from [extent.shp] and MULTIPART TO SINGLEPART to get [NWI_voids_single.shp].
f) SELECT BY LOCATION from [NWI_inclusive_single.shp] that are completely within the [MU_mask01.shp] and SELECT BY LOCATION from [NWI_voids_single.shp] that are completely within the [MU_mask01.shp]. If any of additional polygons need to be removed from the mask include them in a new feature layer [erase_mask_manual.shp]. Merge all three feature sets to get polygons to be excluded [erase_inside.shp] from the final masks.
g) ERASE [erase_inside.shp] from [MU_mask01.shp] and [UVVR_mask01.shp] to obtain [MU_mask.shp] and [UVVR_mask.shp], respectively.
Source_Used_Citation_Abbreviation: NWI
Source_Used_Citation_Abbreviation: NYSDEC
Process_Date: 2020
Process_Step:
Process_Description:
Define preliminary boundaries for marsh units by basin analysis:
a) EXTRACT BY MASK from mosaicked elevation dataset 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 and convert RASTER TO POLYGON. CLIP the polygon with 1-meter buffered marsh units mask [MU_mask_buff1m.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. MULTIPART TO SINGLEPART and ADD GEOMETRY ATTRIBUTES(Geometry properties=Area_geodesic; Area unit=Square_meters) to get [basin_single.shp]
Process_Date: 2020
Process_Step:
Process_Description:
This step merges the "orphan marsh units", units that are less than 5000 m^2 in area 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 ArcMap tools to aggregate orphan units on parent units is used:
a) Create orphan marsh units features by exporting marsh units with an area less than 5000 m^2 [lt5000.shp].
b) Create parent marsh units features by exporting marsh units with an area greater than or equal to 5000 m^2 [ge5000.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. Script will iterate until there is no change in the number of parent or orphan marsh units.
d) 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.
e) MULTIPART TO SINGLEPART to have single part polygons with unique identifiers.
f) UNION(with gaps) single part features with parent units to obtain preliminary marsh units [pMUopt1.shp].
g) SMOOTH POLYGON(Smoothing algorithm=PAEK; Smoothing tolerance=15 meters) to get the smoothed marsh units polygon [pMUopt1_smooth.shp].
h) 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]
i) Compute the final marsh units by removing any artefacts 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 artefacts.
j) DISSOLVE the conceptual marsh units to get the final outlines for the marsh complex [CMU_mask_final.shp].
Process_Date: 2020
Process_Step:
Process_Description:
Determine the vegetated and unvegetated areas by image processing.
a) EXTRACT BY MASK from elevation raster [elev_mosaic.tif] using [UVVR_mask.shp] polygon. Rescale the elevation raster values to the same range with 8-bit NAIP imagery (0 to 255) using min-max scaling. Perform ISO CLUSTER UNSUPERVISED CLASSIFICATION with 4-bands (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]. For marsh units with invalid elevation data, the classification was processed with imagery bands only and later merged with the rest of the dataset.
b) 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(Number of neighbors=4; Zone grouping method=Within; Add Link field to output) to get the [UVV_region.tif], and TEST("Count" less than 9) to set a threshold value of 9 raster cells [UVV_test.tif]. Use RASTER CALCULATOR to toggle the value of the Link field in the region raster, where the test raster indicates regions with areas smaller than the threshold.
c) RASTER TO POLYGON(Simplify polygons=False) and CLIP with the final marsh complex outline [CMU_mask_final.shp] to obtain [UVVc_filt_clip.shp].
d) REPAIR GEOMETRY and DISSOLVE(Create multipart features=False) to get filtered, clipped and dissolved unvegetated-vegetated polygons [UVVc_filt_clip_diss.shp].
e) INTERSECT the final conceptual marsh units [CMU.shp] with unvegetated-vegetated polygons [UVVc_filt_clip.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, Area_geo.SUM) and REPAIR GEOMETRY to get [UVV_poly_diss.shp]. Edit the fields to have "TYP", "APGN_M2", and "ATOT_M2" fields for type of polygon indicating vegetated or unvegetated, surface area of the polygon, and total surface area of the marsh unit, respectively.
f) Add field "UVVR" and calculate unvegetated to vegetated ratio based on "TYP", "APGN_M2" and "ATOT_M2" fields. If the vegetated area is zero for a marsh unit set the value of UVVR to -1.
g) Calculate the mean elevation for each marsh unit with ZONAL STATISTICS AS TABLE(Raster layer=[elev_mosaic.tif]; Zone features=[CMU.shp], Zone field=FID_CMU; Statistics type=Mean; Ignore Nodata=True) and JOIN with [CMU.shp] to get [mu_elev.shp].
Source_Used_Citation_Abbreviation: NAIP
Process_Date: 2020
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 each marsh unit.
b) Add field "FLG" to flag anomalous marsh units based on elevation, surface area, and absence of vegetation. 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 0.2 percentile; (-1000) marsh unit surface area less than 900 m2; (-10000) mean tidal range of marsh unit is extrapolated; and (0) no flag. Combination of negative values indicate combination of flags. For example, -1001 indicates no vegetated area and area less than 900 m^2.
c) Remove field "UVVR" and rearrange field names and change the projection for better performance of web services with online base maps. PROJECT(Input coordinate system=NAD 1983 UTM Zone 18N; Output coordinate system=WGS 1984 Web Mercator Auxiliary Sphere; Geographic transformation=WGS 1984 (ITRF00) to NAD 1983) the feature dataset to obtain the final conceptual marsh units [CMU_HvNYC.shp].
Process_Date: 2020
