Effects of sediment grain size and channel slope on the stability of river bifurcations

Channel bifurcations can be found in river network systems from high gradient gravel-bed rivers to fine-grained low deltas. In these systems, often evolve asymmetrically such that one downstream channel silts up and the other deepens and, most cases, they eventually avulse. Past analytical numerical studies showed symmetric are unstable Shields stress conditions resulting asymmetric avulsion, while stable mid-Shields range, but this range is smaller for larger width-to-depth ratio. Here, using a one-dimensional (1D) model, we show effects of sediment grain size slope much than expected low-gradient when transport relation used separates between bedload suspended load transport. We with expanded lower slopes finer sediment. mobility, increasingly dominates transport, which increases nonlinearity lowers relative influence stabilizing transverse bedslope-driven flux. Contrary previous works, another solution stress, only occurs small This indicates load-dominated lowland more likely develop into highly channels previously thought. explains tendency avulsion observed many systems.