Analysis and Modelling of River Meandering

“Analysis and Modelling of River Meandering” examines the morphological changes of nontidal meandering rivers at the spatial scale of several meanders. With this purpose, a physics-based mathematical model, MIANDRAS, has been developed for the simulation of the medium-term to long-term evolution of meandering rivers. Application to several real rivers shows that MIANDRAS can properly simulate both equilibrium river bed topography and planimetric changes. Three models of different complexity can be obtained by applying different degrees of simplification to the equations. These models, along with experimental tests and field data, constitute the tools for several analyses. Channel migration coefficients are demonstrated to depend not only on physical properties of the eroding bank, but also on physical properties of the accreting bank and the numerical scheme. Moreover, they need to account for overbank flows. Model results and a reexamination of experimental observations suggest that intrinsic initiation of meandering is not necessarily related to steady bars due to a permanent upstream disturbance. They may also be related to a steady bed deformation due to small quickly-varying periodic or random disturbances, for instance due to the presence of migrating alternate bars.