HR: 0800h
AN: H41D-0759    [Abstracts]
TI: Numerical Study of Growth and Degradation of Fluvial Hanging Valleys due to Climate Variability
AU: * Goode, J K
EM: jgoode@crustal.ucsb.edu
AF: Department of Earth Science, University of California, Santa Barbara, CA 93106, United States
AU: Burbank, D W
EM: burbank@crustal,ucsb.edu
AF: Department of Earth Science, University of California, Santa Barbara, CA 93106, United States
AB: An increased rate of base level fall may cause a knickpoint to migrate up a trunk stream and tributaries within a drainage basin. Recent studies have focused attention on those tributaries that are unable to incise as quickly as the trunk stream. As a consequence, hanging fluvial valleys form at these tributary mouths. Such stationary knickpoints at tributary mouths are uncommon, and where found, their height and occurrence is limited. Given a theory for how such hanging valleys can form, this study addressed the question of why they are not more common. A numerical model of bedload-saltation erosion for a tributary junction experiencing base-level fall demonstrates how such hanging valleys may form and subsequently degrade through perturbations in climate- controlled parameters. Increased frequency of bedload mobilization and enhanced bedload supply can drive the degradation of hanging fluvial valleys. In particular, when channel aggradation overtops a knickpoint, the knickpoint tends to be removed during subsequent degradation of the alluvial surface. Channel narrowing, larger bedload clasts, and increased bedload supply are factors that could inhibit the formation or maintenance of hanging fluvial valleys. Although bedload-saltation models predict that hanging valleys should be quite common in regimes of rapid erosion, the frequency and magnitude of climatically induced change in sediment loads typically overwhelms those factors that, in the absence of such bedload variability, promote hanging valley formation.
DE: 1815 Erosion
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting