A case study of the processes displacing flow from the anabranching Ovens River, Victoria, Australia

Anabranching rivers have been well described and location-for-time models suggest that anabranches evolve through stages from channel development to eventual abandonment. Yet, there is much we do not know about the evolution of these systems. Our understanding of why anabranches evolve, how How is displaced onto the floodplain or what propagates the scouring of an avulsion channel is not complete. The objective for this study was to understand how flow is displaced from the channel of an anabranching river. We based our analysis on the location-for-time model developed by Schumm et al. (1996) for anabranching. They proposed that anabranching develops as an individual channel evolves to become less hydraulically efficient, displacing flow onto the floodplain and scouring a new channel. We used geomorphic interpretation and hydraulic models embedded in the location-for-time model to determine how flow is displaced on the Ovens River, Victoria, Australia. Meander extension and, to a lesser extent, vertical accretion were found to reduce the energy expended in channels and drive the changes that displace flow onto the floodplain. This displaced flow potentially initiates an avulsion, the scouring of a new channel. Copyright (c) 2007 John Wiley & Sons, Ltd.