| The Illinois River watershed, in northwest Arkansas, is of critical interest within the region because of land use changes in the headwaters due to rapid population growth. Little knowledge of the geomorphology of headwater streams in the Ozark Plateaus region of northwest Arkansas exists. Headwater streams respond quickly to disturbance and are the majority of stream length within a given watershed. The first two papers in this dissertation focus on the differences in channel geometry and sediment dynamics within urban, agricultural, and forested watersheds Analysis of longitudinal profile, cross-section and sediment distribution in streams from each land use type shows a strong trend of increasing slope and channel cross-sectional area with a greater degree of anthropogenic disturbance. Additionally, urban streams are characterized by the presences of exposed bedrock in the stream bed, while agricultural and forested streams have a continuous sediment mantle. Bed sediment is a mixture of gravel and cobbles and generally less than 15% of the sediment was finer than 2 mm. In urban streams the transition from first to second order streams with first order tributaries represents a threshold beyond which no bedrock is exposed. These data have important implications for current and future stream management policies and practices regionally.;The final paper places the Illinois River Watershed within the context of the regional landscape. The Ozark Plateaus Physiographic Province is noted for the unusual compound river valleys in which the streams are considered unusually small compared to the size of the valleys. Through an examination of the stream/valley architecture in relation to the theory of underfit streams as described by George H. Dury. He developed mathematical relationships between the valley meander wavelength and the stream meander wavelength to define the underfit condition. Spatial analysis of Digital Raster Graphics, Digital Elevation Models, and U.S. Geological Survey Hydrology data sets could not replicate Dury's results. Although this research could not validate Dury's theory, it did highlight significant similarities in basin morphometry throughout the region. Also the results suggest that modem valley architecture regionally is a result predominantly of structural controls and secondarily hydrologic controls. This is a significant observation that will inform future research into the evolution of these compound valleys regionally. |
