Bedload transport in a river confluence
2015; Elsevier BV; Volume: 250; Linguagem: Inglês
10.1016/j.geomorph.2015.07.050
ISSN1872-695X
AutoresJuan Pedro Martín Vide, A. Plana-Casado, A. Sambola, Sergio Capapé Miralles,
Tópico(s)Soil erosion and sediment transport
ResumoThe confluence of the regulated Toltén River and its tributary the unregulated Allipén (south of Chile) has proved dynamic in the last decade. Daily bedload measurements with a Helley–Smith sampler, bed surveys, and grain-size distributions of the two rivers are obtained from a field campaign that lasts 3 months in high-flow season. The goals are to quantify total bedload and to understand the balance between tributary and main river and the bedload distribution in space and texture. The bedload transport varies 200-fold, with a maximum of 5000 t/day. The discharge varies five-fold, with a maximum of 900 m3/s. Two-thirds of the total bedload volume are transported through the deeper area of the cross section and gravel is predominant (64%). Average bedload volumes in the confluence seem unbalanced in favour of the tributary. Main river bedload transport is predominantly at below-capacity conditions, while the tributary bedload transport is at-capacity conditions. This is deemed the main reason of inaccuracy of the bedload predictors. The roles of entrainment into suspension, helical flow, partial transport, and mobile armour are discussed.
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