Mean tidal range of marsh units in Atlantic-facing New Jersey salt marshes

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 the 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 unless otherwise stated.
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_NJ_Atl.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=GCS NAD 1983) the feature dataset to obtain dissolved marsh units [mu_diss.shp].

Generate a point cloud of coordinates indicating calculation locations for the mean range of tides (MN).
a) CREATE CONSTANT RASTER with 50 m spacing (Constant value= 0; Output cell size: 50) that surpasses the marsh unit boundaries by 300m.
b) RASTER TO POINT to generate an array of points [pts.shp]. PROJECT [pts.shp] to GCSNAD 1983. Calculate latitude and longitude of each point [pts.shp]. Export the shapefile to a text file (TABLE TO TABLE (output table= [Tidal_Points.txt])). This text file includes latitude, longitude and height (set to zero).

Calculate Mean Range of Tides (MN) using the VDatum (v.4.5.1) database covering this region. Mean range of tides (MN) = mean high water level (MHW)- mean low water level (MLW) in the VDatum database. Interpolate MN to the point dataset.
a) Input point cloud file [Tidal_Points.txt] to VDatum. Set the REGION (contiguous US; CB/DE Bay), HORIZONTAL INFORMATION (Reference Frame (NAD83-2011; IGS14), Coordinate System (Geographic)) to be the same for the source and target. Set the VERTICAL INFORMATION (Source Reference Frame: MHW (meters); Target Reference Frame: MLW (meters)). Choose ASCII FILE CONVERSION (exclude NODATA points) and save output [MN.txt]. The resulting text file includes latitude, longitude and MN.

Create a raster surface dataset from the feature points.
a) Convert points from [MN.txt] to a shapefile using MAKE XY EVENT LAYER (Z field= Value; Spatial Reference: GCS_NAD_1983; Layer Name: MN_lyr) and COPY FEATURES [MN.shp].
b) Create a raster surface with inverse distance weighting. IDW (Input point features: [MN.shp]; Output Cell Size=0.0001 degree; Power=2; Search Radius=Variable; Number of Points=12; Input barrier polyline features – if necessary) to obtain [MN_raster_idw.tif]. After running this tool, it may be apparent that input barrier polyline feature(s) need to be created to separate areas of unrelated tidal range data (e.g., where values from one body of water cross land to another body of water); in those cases, this tool was re-run with the input barrier polyline features specified.

Clip the raster to marsh boundaries. A buffer zone is created around the marsh boundaries to facilitate alternative interpolation and clipping options in future studies.
a) Create 300 m buffer around the marsh units polygons [mu_diss.shp] to create a clipping mask [mu_buff300m.shp]. BUFFER (Side type= Full; Method =Geodesic; Dissolve type= All).
b) CLIP the raster [MN_raster_idw.tif] with the clipping mask. EXTRACT BY MASK (Mask=[mu_diss.shp]) to obtain [MN_IDW_MU.tif].

Calculate mean tidal range value for each marsh unit and flag the marsh units that have tidal range values that are extrapolated.
a) ZONAL STATISTICS AS TABLE (Feature Zone Data=[mu_diss.shp]; zone field=FID_CMU; Value Raster=[MN_IDW_MU.tif]; Output Table=[mn]; Statistics type=MEAN).
b) JOIN FIELD (Input table=[mu_diss.shp]; Input join field=FID_CMU; Join Table=[mn]; Output join field=FID_CMU; Join Field= MEAN). Export dataset as a shapefile [mu_MN_NJ_Atl.shp] and change “MEAN” to “MN.”
c) Identify marsh units that are greater than 25 m from the VDatum data. SELECT BY LOCATION (Input feature= [mu_diss.shp]; Relationship=within_a_distance; Selecting Features: [MN.shp]; Search distance= 25m; Selection type= New_Selection; Invert Spatial Relationship). Assign the marsh units with a distance greater than 25 m from VDatum data a tidal range value of -9999 and a “flag” of -10000.
d) 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 square meters; (-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 square meters.
e) Rearrange fields 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 mean tidal range dataset [mu_MN_NJ_Atl.shp].