Author(s): Dean Judd; Robert Keller; Ian Rutherfurd; John Tilleard
Linked Author(s): Robert Keller
Keywords: Vulsion; Anabranching; Floodplain evolution; Erosion initiation; Crevasse splay
Abstract: The scouring of a new river channel, an avulsion, is important to river and floodplain evolution. Despite their ubiquity in Australia, the initiation of avulsions and anabranching river patterns is poorly understood. This inhibits the research and management of many of Australia's river systems. Researchers have proposed a number of ways in which avulsions are initiated, but there have been no quantitative tests of the various explanations. In this study, we use quasi-two-dimensional numerical hydraulic modelling to explore the initiation mechanisms for avulsions. The modelling, applied to a case study on the Ovens River, suggests that the key mechanism for the development of avulsion channels is upstreamprogressing scour from the flow re-entry point at the downstream end. Initiation from a paleochannel or deferred junction tributary is also possible. Furthermore, it was found that, contrary to previously-published work, an avulsion was not initiated by major floods. Rather, it was initiated by small to moderate low recurrence interval flood events.
Year: 2007