Abstract:

The unique geometric boundary characteristics of alluvial bends result in distinct water and sediment transport behaviors and bed evolution dynamics compared to other channel types. To simulate the natural evolution of riverbed scour and siltation in alluvial bends, we employed a natural modeling approach to replicate a representative bend channel in a laboratory flume to investigate the influence of varying water and sediment conditions on the formation and development of bends. The experiments reveal the following: 1) A longer cycle of incoming sediment with lower intensity results in a quicker attainment of dynamic equilibrium in the curved river channel, with a narrower stable channel width. 2) Throughout the formation and development of the bend, morphological changes in the channel are primarily dominated by the prevailing water and sediment conditions. 3) Specifically, within a certain range of variation, shorter cycles of sediment transport, reduced incoming flow rate, and higher sediment concentrations facilitate the development of a more pronounced curvature in the channel. 4) Conversely, higher flow rates causing scouring of shallow areas tend to shape the bend into a wider and shallower cross-section. The adjustments in channel curvature and cross-sectional morphology are predominantly driven by changes in water and sediment transport dynamics, highlighting their significant role in shaping channel morphology.

Key words: curved river channel, bed formation process, evolutionary mechanism, channel morphology, natural model, model test