HR: 0800h
AN: H51A-0170    [Abstracts]
TI: Flow structures and controls at river bifurcations: a laboratory flume experiment
AU: * Parsons, D R
EM: d.parsons@see.leeds.ac.uk
AF: University of Leeds, Woodhouse Lane, Leeds, LS29JT, United Kingdom
AU: Best, J L
EM: jimbestjb@aol.com
AF: University of Illinois, Green Street, Urbana, IL 61801, United States
AU: Lane, S N
EM: s.n.lane@durham.ac.uk
AF: University of Durham, University Road, Durham, D217LE, United Kingdom
AU: Thomas, R E
EM: r.thomas@see.leeds.ac.uk
AF: University of Leeds, Woodhouse Lane, Leeds, LS29JT, United Kingdom
AU: Keevil, G
EM: g.keevil@see.leeds.ac.uk
AF: University of Leeds, Woodhouse Lane, Leeds, LS29JT, United Kingdom
AU: Hardy, R J
EM: r.j.hary@durham.ac.uk
AF: University of Durham, University Road, Durham, D217LE, United Kingdom
AB: River bifurcations are key nodes within fluvio-deltaic systems and in braided rivers, the mechanics controlling the flow and sediment partitioning at such sites being the key controls on dynamics of river braiding and distributary systems. Recent research has shown that certain geometrical configurations induce instabilities that lead to downstream mid-channel bar formation. However, to date, we have a poor process understanding of flow dynamics within and through channel bifurcations and their downstream distributary channels and we know very little on the flow division process and its overall controls. This paper presents results of a series of experiments from a flume laboratory study that were conducted in a dedicated facility in the Sorby Environmental Flow Dynamics Laboratory at the University of Leeds. A series of detailed three-dimensional velocity measurements were made at controlled cross sections through the bifurcation model. These measurements were made at equal input discharges but with different downstream weir conditions in the bifurcate channels, essentially controlling water surface slopes through the system. The results indicate that flow division occurs close to the point of bifurcation in all cases. Results also indicate that the influence of the downstream water elevations are very significant; dividing the flow farther upstream than in the equal weir height case and altering the flow structures through this zone. Results also indicate that secondary flows induced at ethe bifurcation and just upstream play an important role in the downstream bifurcate channels, which will have implications for overall system dynamics.
DE: 1825 Geomorphology: fluvial (1625)
SC: Hydrology [H]
MN: 2007 Fall Meeting