ABSTRACT
In the pioneering study of the Ishikari River, Japan, Kinoshita (Kinoshita 1957, 1961) described two types of meandering channels: (1) channel with two bars per meander wavelength (one bar per bend), and (2) channel with three or more bars per meander wavelength (multiple bars per bend). Based on the study of Whiting & Dietrich (1993a,b), we assess the capabilities of the Telemac-Mascaret modelling system (2014) to reproduce Two-Dimensional (2D) and Three-Dimensional (3D) flow and morphodynamics structures in large-amplitude meandering channels. The large-amplitude meander setup of Whiting & Dietrich (1993a, b) was shown to be a difficult test for a depth-averaged 2-D model: even if appropriate parameterizations of relevant 3D effects are incorporated into the model, numerical simulations failed to capture some 3D patterns, such as the first well-defined pool observed in the experiments. However, 3D results obtained from the numerical solution of the RANS equations showed that most of the observed flow and morphodynamics patterns (e.g., series of shingled bars with pools along the concave bank, depositional bank fronts along the inner bank) are well captured by the model. In agreement with experimental observations, the bed topography in large amplitude symmetric planforms can be divided into different zones according to the different morphodynamics patterns: a zone with an almost zero bed load discharge and bed evolution, an “alternate bars” zone, a “shingle-bars zone” and a “multiple-pools” zone.
