Abstract
National Wetland Inventory (NWI) maps are widely used in the United States but have not been independently evaluated in the Great Lakes region nor in forested areas with level topography. Field data from 148 plots in the Hiawatha National Forest ecological classification and inventory program were combined with an additional review to evaluate NWI mapping accuracy. NWI maps were over 90% accurate in identifying uplands and jurisdictional wetlands. All nonforested wetlands were identified correctly. Uplands were correctly identified 96.9% of the time. The lowest level of accuracy, 90.7%, was achieved in identifying forested wetlands. The most common error was the NWI classification of wetlands on the AuGres soil series, a somewhat poorly drained upland soil that often occurs in complexes with wetland soils in the region. Forested wetlands with a cover type similar to adjacent uplands were also a source of error on NWI maps. The already high accuracy of NWI maps could be improved by the mapping of wetland-upland complexes, a development corresponding to the increased mapping of hydric-nonhydric soil complexes in area soil surveys. The continued refinement of regional lists of hydrophytic vegetation is supported by indicator status discrepancies between an extensive Hiawatha National Forest database and the current NWI list for the region.
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Kudray, G.M., Gale, M.R. Evaluation of National Wetland Inventory maps in a heavily forested region in the upper Great Lakes. Wetlands 20, 581–587 (2000). https://doi.org/10.1672/0277-5212(2000)020[0581:EONWIM]2.0.CO;2
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DOI: https://doi.org/10.1672/0277-5212(2000)020[0581:EONWIM]2.0.CO;2