Successful management of natural and engineered channels with discontinuous alluvial cover requires knowledge of how the cover develops and evolves. We report on physical model experiments designed to compare alluvial cover dynamics in straight and sinuous fixed‐bed channels at a range of gravel‐bed material supply rates and constant discharge conditions. Experiments investigated the formation of alluvial cover from a bare bed, relationships between equilibrium cover characteristics and sediment supply rate, and the evolution of an initial uniform cover of varying thickness. A stable partially‐alluviated state is achieved in both the straight and sinuous channels for a range of sediment supply rates. The areal extent and stored mass of the cover increase progressively with supply rate, and the rate of increase is higher in the straight channel. While alluvial cover develops from isolated patches in the straight channel, cover in the sinuous channel develops as well‐defined bars, with deposition on the inside of bends and expanding outwards along the channel as cover area increases. Artificially emplaced cover quickly adjusts to a cover extent within 4–20% of that formed from a bare bed at the same feed rate, with initial cover thickness only influencing the final cover in the sinuous channel. Neither the sinuous nor the straight channel can sustain an alluvial cover in the absence of upstream sediment supply. This study can inform the management of semi‐alluvial channels because it highlights the primary roles of sediment supply and planform geometry in maintaining an alluvial cover in natural and engineered channels.

中文翻译：

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砾石充填法在平缓河道冲积层恢复试验

要成功管理具有不连续冲积层的自然通道和工程通道，需要了解其如何发展和演变。我们报告了一些物理模型实验，这些实验旨在比较在一系列砾石床物料供应速率和恒定排放条件下，直线和弯曲固定床通道中的冲积层动力学。实验研究了从裸露的床形成冲积层，平衡覆层特征与沉积物供应速率之间的关系以及不同厚度的初始均匀覆层的演化。在一定范围的沉积物供应速率下，直通道和蜿蜒通道均达到了稳定的部分淹没状态。覆盖物的面积和存储质量随着供给速率的增加而逐渐增加，并且在直通道中增加的速率更高。冲积层是由直通道中孤立的斑块形成的，而蜿蜒通道中的覆盖层则是条形清晰的条形，沉积在弯头内部，并随着覆盖面积的增加沿通道向外扩展。人工覆盖的覆盖层可以在相同的进给速率下快速调整到覆盖范围为裸床形成覆盖层的4–20％，初始覆盖层的厚度仅影响弯曲通道中的最终覆盖层。在没有上游沉积物供应的情况下，弯曲通道和笔直通道都不能维持冲积层。这项研究可以强调半冲积河道的管理，因为它突出了沉积物供应和平面形状在保持天然和工程河道冲积层中的主要作用。