As we finish creating digital representations, or features, of historical water bodies for our project to create a dataset of historical water bodies in New Jersey, we begin exploring how these water bodies have changed over time. In GIS, the process of quantifying land cover change over time is known as Change Detection. Esri’s ArcGIS Pro software offers several tools to facilitate this process (Esri, 2025). The following steps were all completed using these tools.
Previously, a feature class was created for each water body type in the historical maps we traced them from: Bay, Lake/Pond, River, Stream, and Wetland. A “Type” field was created in each of these feature classes with a value corresponding to its water body type. These feature classes were then merged using the Merge tool to create a single historical water body feature class which included the “Type” field. All the input feature classes were of the polygon type except for Stream, which is a line feature class. Because all feature classes must be of the same geometry type for the Merge tool to work, the Pairwise Buffer tool (Esri, 2025) was used to create a polygon feature with a five-foot buffer around each line feature before running the Merge tool (Esri, 2025). The Feature to Raster tool (Esri, 2025) was then used to create a ten-foot resolution raster dataset from the merged historical water body feature class. The output raster has a value to each water body type: Stream = 1, River = 2, Lake/Pond = 3, Bay = 4, and Wetland = 5.
NJDEP’s Land Use/Land Cover of New Jersey 2020 (LULC2020) dataset (NJDEP, 2025) was used to examine how the water bodies in our historical maps have changed over time, by comparing it to our historical water body raster. First, all non-water 2020 land covers were selected from LULC2020 and dissolved into a single land feature using the Pairwise Dissolve tool (Esri, 2025). Then the Feature to Raster tool was used again, this time to create a ten-foot resolution raster from this dissolved land feature with a value of one. The Raster Calculator tool (Esri, 2025) was then used to first add five to the land raster, giving it a value of 6, and then subtract the historical water body raster was subtracted from it. If a historical water body was present in the historical water body raster where land was in the land raster, then its value was subtracted from the land value. Finally, the Calculate Field tool (Esri, 2025) was used to create a new field in the final output, indicating which historical water body type existed where today there is land based on the raster calculations.
References:
Esri. (2025). Change Detection in ArcGIS Pro. https://pro.arcgis.com/en/pro-app/latest/help/analysis/image-analyst/change-detection-in-arcgis-pro.htm.
Esri. (2025). Pairwise Buffer (Analysis). https://pro.arcgis.com/en/pro-app/latest/tool-reference/analysis/pairwise-buffer.htm
Esri. (2025). Merge (Data Management). https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/merge.htm.
Esri. (2025). Feature to Raster (Conversion). https://pro.arcgis.com/en/pro-app/latest/tool-reference/conversion/feature-to-raster.htm.
NJ Department of Environmental Protection, Bureau of GIS. (2025). Land Use/Land Cover of New Jersey 2020. https://njogis-newjersey.opendata.arcgis.com/search?q=Land%20Use%2FLand%20Cover
Esri. (2025). Pairwise Dissolve (Analysis). https://pro.arcgis.com/en/pro-app/latest/tool-reference/analysis/pairwise-dissolve.htm.
Esri. (2025). Raster Calculator (Spatial Analyst). https://pro.arcgis.com/en/pro-app/latest/tool-reference/spatial-analyst/raster-calculator.htm.
Esri. (2025). Calculate Field (Data Management). https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/calculate-field.htm.