HR: 10:50h
AN: H42B-03    [Abstracts]
TI: Modelling the Effects of Coarse Vegetation on Braided Stream Pattern and Dynamics
AU: * Coulthard, T J
EM: T.Coulthard@aber.ac.uk
AF: Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, SY23 3DB United Kingdom
AB: Investigations using a 16m by 2m recirculating experimental flume model of an ephemeral braided river indicate that the presence of large and erosion resistant plants within the channel (e.g. trees or shrubs) can have a significant impact on channel pattern and plan form dynamics. Simulations show that these plants have two effects. First, they act as obstructions, in some cases forcing the flow to divide. This flow separation can allow the deposition of a small island immediately in the lee of the plant splitting the channel. The net result is a substantial increase in the number of channels and correspondingly the braid index. This is in direct contrast to previous studies, where increased levels of vegetation in perennial streams have decreased the braid index. Second, the plants stabilize braid bars and can form relatively stable islands in their lee, significantly reducing the longitudinal and lateral migration of islands typically associated with braided rivers. These results may have imporant implications for our understanding and management of braided rivers, as well as how vegetation interacts with flow and sediment transport.
UR: http://www.coulthard.org.uk
DE: 4558 Sediment transport
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting