The Appalachian Mountain Club (AMC) has completed 132 fish passage restoration projects and reconnected 128 stream miles in Maine's 100-Mile Wilderness. However, inaccuracies in publicly accessible data resources, such as the USGS National Hydrology Dataset (NHD), prompted the need for a more precise stream delineation model.
In 2020, AMC launched a pilot project using GPS stream field data as a benchmark, referred to as the “GPS Streams,” to develop a model using ArcMap's Spatial Analysis package. This initial model was later refined in ArcGIS Pro using the ArcHydro package, which is specialized for hydrologic analysis within the ESRI suite. The model adheres to ESRI’s ArcHydro: Overview of Terrain Preprocessing Workflows. The model was tested with one-, three-, and five-meter DEMs. The five-meter DEM provided the most accurate results compared to the GPS streams, as one- and three-meter DEMs overestimated stream lengths and density. Various Stream Definition thresholds were tested, and a threshold of 5000 cells was found to be most similar to the GPS streams.
To assess the model, the lengths of modeled streams were compared to GPS stream lengths using ESRI’s base tools. Errors between the modeled and GPS streams were calculated to determine under- or over-estimation. The model tended to over- or under-estimate stream lengths by at least 10%, likely due to the lack of topographic variability and interference from wetlands and forest types in the MWI area.
The integration of ArcGIS Hydro tools significantly enhanced the accuracy of stream and wetland delineation, supporting the AMC’s mission to protect aquatic ecosystems and aiding resource management agencies in making informed decisions. This initiative underscores the critical role of precise geospatial data in environmental conservation and habitat restoration.
