Hydrodynamics and channel morphology at a braided-meandering river confluence

Guerrero L.; Konsoer K.M. · Geomorphology (2026) · DOI: 10.1016/j.geomorph.2026.110439

Resumen

River confluences are critical nodes in fluvial networks, characterized by abrupt changes in hydrodynamics, sediment transport, and channel morphology. While extensive research has focused on single-thread confluences, little is known about junctions where a braided tributary interacts with a meandering river. This study examines the confluence of the tributary Colorado River with the meandering Madre de Dios (MDD) River in the southwestern Amazon Basin using satellite remote sensing and field measurements across contrasting hydrologic conditions. During low-discharge, flow within the braided Colorado River is confined to isolated thread, resembling single-threaded confluences. In contrast, during relatively high-discharge, flow expands across the full width of the braided channel, resulting in a broad mixing interface where water, momentum, and sediment from the braided river are continually input and interact with the MDD River. Under high-discharge and low momentum ratios, flow is advected across extensive braid bars at the mouth of the Colorado River due to curvature of the meandering MDD River, leading to complex three-dimensional flow structure and the development of a shallow shear layer and mixing interface. Repeat satellite and field observations reveal that the bed morphology at this confluence is highly dynamic, greatly influencing the hydrodynamics as flow responds to rapid changes in width-depth ratios. These findings provide new insights into mixing processes, sediment routing, contaminant transport, and ecological variability in large, complex river systems.

Instituciones: Universidad de Ingeniería y Tecnología