Use of created Wetland delineation and weighted averages as a component of assessment

Abstract

Forested wetland creation for compliance with Section 404 of the Clean Water Act is increasing dramatically throughout the Mid-Atlantic region of the United States. However, no quantitative data are available regarding the effectiveness of past forested wetland creation efforts in this region, and no quantitative assessment techniques for evaluating success have been developed. Created wetlands may lack sufficient time for soil formation; however, colonizing vegetation and hydrology may be considered indicators of existing conditions. Hydrology monitoring is expensive, time-consuming, and highly variable over short time periods. This study was designed to test the hypothesis that one parameter (vegetation) could be used to evaluate early site conditions following wetland creation. We attempt to show the advantages and disadvantages of using vegetation to calculate percentage “wetland” and “upland” as an early monitoring tool. Calculations were made using the 1989Federal Manual for Identification and Delineation of Jurisdictional Wetlands, colonizing vegetation weighted average, site moisture estimates, and comparisons with an adjacent reference wetland. Percentage “wetland” and “upland” estimates were similar whether vegetation alone or vegetation in combination with hydrology was used in calculations. Vegetation colonizing the site may respond to both soil and hydrology and may provide an early indication of conditions within created wetlands. The findings of this study suggest that calculating plot-weighted averages and comparison with pre-impact wetland vegetation (or an adjacent reference wetland) may be a useful component of a monitoring scheme for certain created wetlands.