Two common methods are currently used to delineate wetlands.  The US Army Corps of Engineers' (ACOE) wetland delineation method utilizes field hydrology, soil, and vegetation indicators.  The US Fish and Wildlife Service (USFWS) relies on remote sensing technology to create wetland maps in the National Wetland Inventory program (NWI).   The New York State Freshwater Wetlands Map was created using the NWI method.  This study compared the interpretations of the two wetland delineation methods.  Twenty wetlands listed on the New York State Freshwater Wetlands Map within the Ausable River Watershed in Essex County, NY were selected for this study.  Sampling locations within and beyond each wetland boundary as listed on the wetland map were positioned as a grid across the landscape.  Of the 303 study sites, 236 (78%) were identified as wetlands on the wetlands map; 67 (22%)were bordering the wetlands on the wetland map.  Wetland hydrology, soil and vegetation indicators were observed and recorded following the methods described on the ACOE wetland delineation manual in summers 2008 and 2009.   

Results/Conclusions  

Of the 236 sites considered wetlands by the NWI criteria, 213 (98%) were also considered wetlands by the ACOE criteria. Of the 67 sites not considered wetlands by the NWI criteria, 23 (34%) were also not considered wetlands by the ACOE criteria. There was a discrepancy between the two methods in 67 (22%) of the total 303 sites. This discrepancy in the 23 sites considered wetlands by the NWI criteria but not by the ACOE criteria was due to a lack of hydrology indicators in 20 of the sites (87%). In our study area discrepancies between delineations of wetlands using the two methods were most often caused by the site not meeting the hydrology requirement of the ACOE method.