Stream-Channel Morphology in a Mixed-Bedrock Valley: The Harpeth River Watershed, Middle Tennessee

Abstract

Factors such as lithology, tectonics and climate have been identified as exerting control on the form of stream channels and on the evolution of watersheds. The degree to which these factors interact to influence landscape erosion and its evolution has been an area of extensive research. Here, we use Digital Elevation Models to extract metrics of basin morphology to determine the form and the controls on river long profiles in the Harpeth River Watershed, which drains the Paleozoic carbonate bedrock of the Nashville Basin and the Western Highland Rim. We use the integral approach, which transforms the horizontal coordinate by integrating drainage area over flow distance to produce the transformed horizontal coordinate, χ, along with river long profiles to determine the relative influence of lithology on the form of the river profiles. The results show that drainage area, a proxy for water discharge, exerts the greatest influence on channel geometry in the Harpeth River Watershed as is indicated by m/n values that center around 0.5. Deviations from the linear, χ-transformed elevation profiles that are produced at m/n = 0.50±0.05 were found to be as a result of local differences in bedrock lithology that affect erodibility and sediment production.