A synthetic flow network decision-making tool to identify potential downstream contamination risk in permafrost-bound Alaskan hazard sites

In Alaska, the presence of permafrost was historically considered a functionally impermeable barrier to environmental contamination. However, climate change in Arctic landscapes has drastically increased the emergence of ecological contaminants from permafrost-bound hazard sites. Here, we showcase the development of ArcGIS Pro 3.x custom geoprocessing tool leveraging synthetic flow modeling and downstream trace analysis for community health decision-making. This toolbox returns highlighted at-risk downstream contamination pathways from synthetic flow models of 5-m IfSAR DTM of local watersheds. We investigated four common Alaskan environmental hazard sites (mines, landfills, active/passive clean-up sites, historic cemeteries) in a case study of tool performance (n = 6 test sites). Double-blind model ground truthing using nearest Euclidean distance GIS validation alongside qualitative validation using satellite imagery shows that tool results strongly agree with real-world hydrology (RMSE 5.8–9.4 m, 13 of 15 ground-truth points successfully routed). This provides support for the utility of this toolbox in real-world water contamination research, mitigation decision-making, and climate adaptation planning. Our Contamination Site Tracing Geoprocessing Tool solves two common problems with native tools, providing the ability to 1) integrate area of interest (AOI) polygons as trace network starting points and 2) run multiple trace networks simultaneously. Customizable features highlight the flexibility of AOI and buffer size to delineate questions of whether contaminant inflow versus terminal outflow tracts are of higher interest to users. Despite work to isolate hazardous infrastructure during development, results show that thawing permafrost-bound contaminants can put thousands of meters of watershed at risk in our use cases. In Alaska, environments function as key subsistence hunting and gathering lands for local rural and indigenous communities. Thus, identifying contamination risk for mitigation planning with limited resources is both a matter of land sovereignty and cultural food security. While our ArcGIS Pro 3.x toolbox and associated workflow documentation were developed for the Arctic, this tool is functionally area-agnostic. Using the tool requires an ArcGIS Pro 3.x series license and access to common data such as area hydrology, digital terrain models (DTM), and researcher-generated AOI polygons. We provide recommendations for tool use with the support of our tested case studies and pathways for tool improvement for users interested in contaminant transport beyond surface flow.