Klemow, Kenneth M.*, Malika Mohseni, Jessica Azarewicz, Carrie Chipego, Jane Jesse, and Daniel Siani. 1999. CORRELATION OF NATIONAL WETLAND INVENTORY BOUNDARIES TO IN-FIELD DELINEATIONS: A FOLLOW-UP ASSESSMENT. Contributed paper: Pennsylvania Academy of Science meeting. Abstract: Journal of the Pennsylvania Academy of Science 72:167.
Previous work comparing National Wetland Inventory (NWI) maps to soils maps for an area in northeastern Pennsylvania suggested that NWI maps grossly underestimate Jurisdictional wetland acreage. In this study, we compared NWI maps against in-field delineations for a composite area representing 573 acres throughout Luzerne County, PA. Soil types classified into five drainage categories were added to the maps. The proportion of each drainage category depicted as being in or out of jurisdictional wetland was determined by a point-grid method. For each soil-drainage category, the proportion of area actually containing wetland was consistently higher than that shown by NWI maps. 62% of areas having hydric soils were found to be Jurisdictional wetland, while NWI maps show 34% of hydric soil area as wetland. Corresponding values for areas classified as having subhydric (somewhat poorly drained) soil were 47% (actual) vs 3% (predicted by NWI). This study provides further evidence that NWI maps significantly understate true wetland acreage, at least for for eastern Pennsylvania, and should therefore not be used for Jurisdictional purposes.