By using this data, you agree to the SEMCOG Copyright License Agreement. The full text can be read here: https://maps-semcog.opendata.arcgis.com/pages/copyright-license-agreementNone. Acknowledgement of the U.S. Fish and Wildlife Service and (or) the National Wetlands Inventory would be appreciated in products derived from these data. Historical wetland data produced from existing soils surveys, are obvious approximations of wetland extent and condition. NWI Coding for Pre-European Settlement wetland polygons was derived from soil characteristics, and checked against Pre-European Settlement vegetation maps produced by interpreting GLO Surveys from the early 1800s. This required an approximation of flooding and ponding frequency (water regime), as well as vegetative cover. Given that landform information in this analysis was derived from NWI water regime, certain types of landform (fringe, slope, etc) may be underrepresented in the Pre-European Settlement coverage. Pre-European Settlement hydrology was approximated using current surface water data, and checked with GLO Surveys. Streams that appeared to have a natural channel, were major courses, or were denoted as undisturbed in the attribution were included in the Pre-European Settlement analysis. The 2015 NWI data should be an accurate reflection of wetland extent and condition within the State of Michigan. However, given the inherent limitations of using a data source that is mainly derived from aerial photo interpretation, care should be exercised when using the results of this analysis. Issues with photo quality, scale, and variable environmental conditions should be taken into consideration when interpreting this information (Tiner, 2002). Also, errors of omission and commission are possible. Drier-end wetlands tend to be difficult to interpret on aerial photos, as are forested wetlands where canopy can obscure hydrology below. Because water regime information was interpreted from one snapshot in time, it may not always be reliable in determining seasonal saturation. Many times, the seasonal saturation of wetlands can vary widely over long time periods which can be difficult to account for in this type of mapping effort. This analysis produces a planning tool that can assist in identifying potential wetlands of significance for certain functions. However, no effort was made to compare the relative significance of two wetlands predicted to perform the same function. The W-PAWF also does not consider the condition of adjacent upland or the relative water quality of adjacent waterbodies, which may be considered important factors in determining the overall health and condition of a wetland (Tiner, 2005). No assessment technique on wetland function is likely to be robust enough to first evaluate the level of a particular function and then further distinguish whether the function is part of a human-based value system (Brinson, 1993). Also, it should be noted, that this type of analysis is not intended for a user to take it to the field for the purpose of matching indicators with functions. Rather, this type of analysis is intended to show how some fundamental knowledge about water flows and sources and geomorphic setting can be interpreted to illustrate ecological functioning (Brinson, 1993).
