Modeling the migration of tight bends: a comparison between analytical and numerical approaches for simulating the hydrodynamics and considerations about migration

Currently, only two-dimensional (2D) linear analytical models can be practically used to predict meander migration of rivers at reach-scale. Such models assume that the ratio of channel width to radius of curvature is much smaller than one. Unfortunately, sharp bends are commonly found in nature and in constructed re-meandered channels. Moreover, linear models assume or compute bed topography with a certain degree of idealization. The hydrodynamic fields obtained with 2D linear and fully non-linear models are compared for a restored, highly meandering reach on Trout Creek in the Tahoe Basin, California, USA. Analysis of observed localized bank retreat suggests that a fully non-linear model is required for meander-migration simulations in tight bends, while the overall migration patterns and rates can still be captured fairly well by the linear model.