A Numerical Model of Bank Collapse and River Meandering

Abstract

Meander migration results from the interaction between inner bank accretion and outer bank erosion/collapse. This interaction has been usually treated as a long-term average of a sequence of erosion events determined by flow hydrographs. Little attention has been paid to the role that individual bank collapse events play on meander evolution. To fill this gap, we developed a numerical model of river meandering that describes explicitly bank collapse. Results show that as bend curvature increases due to meander migration and elongation, the initially scattered locations of bank collapse events converge toward the channel section where bed shear stress attains a maximum. Simulations illustrate the observed catch-up behavior between inner and outer banks, driven by intermittent bank collapse events. Moreover, bank collapse is found to speed up short-term meander migration and, consistent with field observations, meanders turn out to evolve toward a state characterized by constant channel width.