WETLAND DELINEATION OF THE NIOBRARA RIVER IN AGATE FOSSIL BEDS NATIONAL MONUMENT

A wetland delineation study was conducted at Agate Fossil Beds National Monument as part of the Geologist in the Park position sponsored by the Association for Women Geoscientists. Agate Fossil Beds National Monument, located 10 miles east of Wyoming and south of Pine Ridge and Black Hills, is a remote hill and valley, 3000-acre park that is located near Harrison, Nebraska. National Wetlands Inventory maps of the area show that wetlands in the park are adjacent to the upper Niobrara River, which flows west to east for the four-mile length of the park. These maps are 20 years old and because this area of the country has been experiencing drought for the past several years; the park delineation of wetlands are inaccurate and need to be updated. For this study, wetlands are defined by three characteristics: hydrophytic vegetation; hydric soils; and wetland hydrology (periodically inundated soils or soils which are saturated some time during the growing season). Additional maps and aerial photographs were used to assist in identifying wetland areas. Subject sites were visually studied to determine the percentage of vegetation within plant community types (herbs, shrubs, and trees) in relation to wetland and non-wetland vegetation. The dominant vegetation was used to determine if wetland was present. Soil pits were used to determine if the soil had the characteristics of hydric soils and if there was or has been sufficient water in the soil for wetland hydrology. GPS data were used to create a wetland delineation map using ArcGis 8.2. Tentative results show the wetland boundary has decreased slightly, approximately 10-15%. These areas which have converted from wetland to upland status are generally very flat low-lying areas adjacent to the river and appear to be sensitive to a slight drop in the water table.