River avulsion is a fundamental mechanism of channel adjustment across fluvial landscapes, occurring not only on low-gradient deltas but also across upper floodplains and alluvial fan systems where rapid sedimentation and gradient shifts promote channel instability. Under a changing climate, the frequency and magnitude of avulsion-triggering conditions may intensify, yet quantitative assessments of avulsion likelihood in Australia remain limited and is rarely assessed in flood studies and floodplain management plans. This paper evaluates avulsion potential in the Lower Burdekin River, north Queensland, integrating sediment budget analysis, hydraulic modelling and geomorphic threshold metrics to assess contemporary and future risk drivers.
The Lower Burdekin is a sand-bed river downstream of Burdekin Falls Dam with a documented Holocene history of delta-lobe switching. Sediment transport modelling indicates the lower river is presently supply-limited, with substantial excess transport capacity that constrains long-term channel aggradation under current conditions. Avulsion likelihood in the delta is therefore more strongly influenced by flood magnitude, duration, floodplain connectivity and backwater dynamics than by sedimentation alone.
Projected increases in extreme rainfall across eastern Australia, recent widespread landslide activation in headwater catchments, and accelerating sea-level rise collectively have the potential to alter sediment delivery, backwater extent and floodplain gradients. These interacting drivers may elevate avulsion probability across both deltaic and alluvial fan environments. Integrating sediment supply, transport capacity and geomorphic thresholds provides a framework for anticipating river adjustment under future climate scenarios.