HR: 17:15h
AN: H54A-06    [Abstracts]
TI: The Interplay Among Vegetation, Bifurcations, Avulsions, and Channel Morphology in an Experimental Channel
AU: * Tal, M
EM: michaltal8@gmail.com
AF: National Center for Earth-surface Dynamics, St. Anthony Falls Laboratory 2 3rd Ave. SE, Minneapolis, MN 55414, United States
AU: Paola, C
EM: cpaola@umn.edu
AF: National Center for Earth-surface Dynamics, St. Anthony Falls Laboratory 2 3rd Ave. SE, Minneapolis, MN 55414, United States
AB: A series of laboratory experiments investigating the interactions between vegetation and braiding demonstrate the interplay between bifurcations, avulsions, channel morphology, and sediment storage and release as the system evolves from unvegetated braided to single-thread with a vegetated floodplain. Vegetation led to net storage of sediment and super-elevation of channels in the experiments. This unstable condition caused channels to avulse, steering the flow into nearby steeper floodplain channels. In contrast with the braided system, where channel switching is a nearly continuous process with persistent flow shifting among multiple channels following slight gradient differences, the vegetated state produced less frequent and more distinct avulsions. Because of the added difficulty of cutting a new path across vegetated surfaces, a channel avulsion required a larger super-elevation which led to abandonment of the old channel and relatively complete diversion of flow to the new one. Channel abandonment at bifurcations under low flow conditions played a key role in vegetation expansion and the incorporation of channels into the evolving floodplain. The steady state system produced quasi-stable states: a dynamic exchange of flow and sediment occurred between anabranches separated by a stable vegetated island. At different times one channel contained the majority of the flow. As the dominant channel filled in with sediment, flow was diverted to the secondary channel and the secondary channel deepened.
UR: http://www.geo.umn.edu/orgs/seds/
DE: 1820 Floodplain dynamics
DE: 1824 Geomorphology: general (1625)
DE: 1825 Geomorphology: fluvial (1625)
DE: 1861 Sedimentation (4863)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: 2007 Fall Meeting