HR: 10:35h
AN: H42B-02    [Abstracts]
TI: Coupling Sediment Transport and Changing Channel Morphology in Response to Vegetation Forcing in a Laboratory Channel
AU: * Tal, M
EM: talx0001@umn.edu
AF: University of Minnesota, National Center for Earth Surface Dynamics, St. Anthony Falls Lab, 2 3rd Ave SE, Minneapolis, MN 55404 United States
AU: Paola, C
EM: cpaola@umn.edu
AF: University of Minnesota, National Center for Earth Surface Dynamics, St. Anthony Falls Lab, 2 3rd Ave SE, Minneapolis, MN 55404 United States
AU: Block, D
EM: bloc0059@umn.edu
AF: University of Minnesota, National Center for Earth Surface Dynamics, St. Anthony Falls Lab, 2 3rd Ave SE, Minneapolis, MN 55404 United States
AB: We report results of an experiment lasting 22 weeks to study the long term evolution of a braided system continuously forced with vegetation and cycled high and low discharges. The duration and intensity of the high discharge, and the seeding density of the vegetation, were set so that channels typically migrated some 10% of their width during one high-discharge event. As a well-established vegetated floodplain develops, one of the braid channels emerges as the dominant channel and begins to widen and become more sinuous. This transition is associated with increases in mean channel depth, and decreases in total wetted width, velocity variability, and depth variability. A main characteristic of the single thread system is that once the channel becomes sufficiently sinuous the flow is no longer capable of removing clumps of vegetation that enter the channel. These debris jams lead to aggradation and flow separation upstream of the jam. This results in the channel eventually being abandoned and a new main channel establishing further upstream. The sediment output from the system was collected at 5-minute resolution throughout the run. The transition from unvegetated braided to vegetated meandering is characterized by sediment storage in the system, reflected in an imbalance between the amount of sediment being fed and the amount exiting the system. In addition it reflects finer scale processes such as the debris jams described above. Based on three tests, the level of recent bar-migration activity seems to have potential for predicting the eventual success of channel devegetation efforts.
UR: http://www.geo.umn.edu/orgs/seds/
DE: 1800 HYDROLOGY
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1851 Plant ecology
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting