COMPARATIVE GEOMORPHIC ANALYSIS OF THREE SUB-WATERSHEDS OF BEAVER RESERVOIR, NORTHWEST ARKANSAS

Understanding and deriving the geomorphometry of watersheds is an important task in understanding and modeling various watershed processes and also allows for a more valid comparison between watersheds. Increasingly, Geographic Information System software is utilized to derive and analyze watershed morphometrics. To evaluate the sensitivity and robustness of morphometric parameters derived from data of differing resolution, three sub-watersheds of Beaver Reservoir, northwest Arkansas were analyzed and compared. The study is part of a larger EPA study relating lake sedimentation to land-use in the same three watersheds. Beaver Reservoir is located in northwest Arkansas along the White River and was created in 1965 by the U.S. Army Corps of Engineers. The surrounding territory is a mixture of wooded valleys and pasture land all underlain by the same geologic formations. Two sub-watersheds (Prairie Creek, Monte Ne Cove) are experiencing extensive land use change associated with explosive urbanization whereas the third watershed (Blackburn Creek) is within a wildlife management area of the Ozark National Forest and is relatively undisturbed. Morphometric properties examined included watershed area, total relief, slope and slope distribution, slope aspect, stream density, and stream profiles. The morphometries of each sub-watershed were derived from newly processed 7.62-m LIDAR elevation data as well as from publicly-available 30-m and 10-m digital elevation data. Initial results of the study indicate that some morphometric parameters are more influenced by the spatial resolution of terrain data, suggesting differences in the robustness of morphometric parameters. Varying parameter inputs to watershed models can also have a large impact on model outputs, so understanding the impact of spatial resolution on parameters is of great importance in determining the meaning and value of model outputs. In this instance, varying derived slopes, stream densities, and resultant stream profiles would significantly impact modeled erosion and sediment flux within the three sub-watersheds.