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Knickpoint form and migration produced by base level lowering at Great Falls, VA
Kee, Connor
Kee, Connor
Abstract
Knickpoints are steepened reaches along channel profiles. They are important in communicating climatic changes such as base level fall throughout river networks and represent a boundary between a downstream landscape which is adjusting to its passing and a relict upstream landscape still in its pre-perturbation form. Although numerous studies have begun to elucidate the nature of these important geomorphic features, direct measurement of their retreat rates upstream are still few and far between. In an effort to add to the growing study of knickpoint form and migration, this study examines knickpoints in the area around Great Falls, VA. Great Falls itself is thought to represent a propagating knickzone that has travelled up the Potomac River, thus spawning subsequent knickpoints along the Potomac’s tributaries. This study utilizes log based area-slope plots to identify the knickzones along 7 tributaries downstream of Great Falls. Age data provided by Bierman et al., (2005) allow for the calculation of a propagation rate for Great Falls, which in turn allows for a calculation of retreat rate for each channel’s knickzone. We plot these rates against drainage area in order to assess the assumption that drainage area controls knickpoint recession and plays a crucial role in bedrock channel evolution.
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2014-01-01
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Geology