Modelling mid-channel bars in meandering channels.

摘要: An analytical modelling framework is proposed to reproduce the frequently observed but poorly studied occurrence of mid-channel bars in meandering channels. Mid-channel occur meanders and may characterize transitional morphologies between pure braided rivers. Based on existing field experimental observations, we propose that two different mechanisms can generate central topographical patterns meanders. A former mechanism (‘width-forced’) related spatial width oscillations which determine a laterally symmetrical bed shear stress pattern promotes bars. second (‘curvature-forced’) take place also curvilinear equiwidth streams since longitudinal variations channel curvature produce alterations sediment transport capacity. perturbation approach employed model both within common framework, allowing reproduction, at least qualitatively, several features. While width-forced are symmetric linear altimetric response, curvature-forced requires nonlinear flow-bed topography interactions order expansion. Hypotheses how these operate further discussed through an application cases. The amplitude response be relevant compared point bar location seldom coincides with bend apexes, mainly depending upon intrinsic meander wavelength. Central tend symmetrically divert flow against banks, process as possible cause cross-sectional overwidening, along asymmetry rates bank erosion opposite accretion. outcomes this first step subject allow discussion mutual feedback processes river Copyright © 2010 John Wiley & Sons, Ltd.