![]() ![]() ![]() In terms of planform migration, the Ucayali is one of the most active rivers in the Amazon Basin, where oxbow lakes, neck and chute cutoffs are common. ![]() It carries one of the highest suspended sediment loads of any of the tributaries to the Amazon River. The Ucayali River is a large meandering river in the Peruvian Amazon Basin that drains an area of 360,000 km 2. However, at high amplitudes, these secondary channels reduce their capacity to capture flow and start a narrowing process, which in turn increases migration rates of the main channels (meandering reactivation process), suggesting that an imminent cutoff along the JH bend is underway by pure lateral migration or by the collapse into the existing paleochannels. Results indicate that the secondary channels have disrupted typical planform migration rates of the main meandering channel. Additionally, a two-dimensional depth average hydraulic model is utilized to correlate observed migrating patterns with the hydrodynamics. For the case of a bend with secondary channels (Jenaro Herrera, JH), detailed field measurements for bed morphology, hydrodynamics, bed and suspended load are performed for low-, transitional- and high-flow conditions (August, February and May, respectively). ![]() Based on remote sensing analysis, a comparison of planform dynamics of bends with and without secondary channels is presented. In the lower portion of the Ucayali River, before its confluence to the MaraƱon River where the Amazon River is born, the increase in water and sediment discharge triggers bends with secondary channels (transitional stage from purely meandering to anabranching), which influence the planform migration rates and patterns of the sinuous channels. The Ucayali River is one of the most dynamic large rivers in the world, with high rates of channel migration regularly producing cutoffs. ![]()
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