The modern Yellow River Delta (YRD) has witnessed frequent channel avulsions followed by the morphological processes of “wandering- short-lived braiding -merging” in history. However, process-based investigation and relevant physics behind these processes remain poorly constrained. The present study complements the understanding for this evolution through numerical experiments. This is achieved by applying a two-dimensional (2-D) depth-averaged fully coupled morphodynamic model that considers the feedbacks of sediment-laden flow and bed deformation to a schematized fan-shaped YRD. Under an uneven bed of uniform sediment, the avulsed processes of “wandering- short-lived braiding -merging” during new channel routing on the YRD are satisfactorily reproduced by the present modelling in terms of the time evolution of planar channel pattern and channel length. Moreover, the mechanisms of the avulsed evolution have been elucidated through factor analysis on delta slope, incoming flow-sediment conditions and artificial trenching, etc. It is suggested that morphological stability could be reached when a single meandering channel is finally sustained, of which the time scale is 4–8 years echoing the documented data of abandoned channels on the YRD. In addition, quantitative criteria have been advocated to help distinguishing the sub-stages of the avulsed evolution together with the characteristic pattern judgement. Based on the above, implications for the YRD management are discussed.

中文翻译：

---

现代黄河三角洲撕脱河道过程的机制和形态时间尺度


近代黄河三角洲历史上曾发生过频繁的河道撕脱，并经历过“漂流-短辫-合并”的形态过程。然而，基于过程的研究和这些过程背后的相关物理仍然受到很少的限制。本研究通过数值实验补充了对这种演变的理解。这是通过应用二维 (2-D) 深度平均全耦合形态动力学模型来实现的，该模型考虑了沉积物流动和河床变形对示意性扇形 YRD 的反馈。在均匀沉积物的不均匀床层下，长三角新河道选线过程中“游走-短命辫状-合并”的撕脱过程通过平面河道格局和河道长度的时间演化得到了满意的再现。此外，通过三角洲坡度、来流泥沙条件和人工挖沟等因素分析，阐明了撕脱演化的机制。表明当单一曲流河道最终得以维持时，才能达到形态稳定，其中时间尺度为 4-8 年，与长三角废弃河道的记录数据相呼应。此外，还提倡使用定量标准来帮助区分撕脱进化的子阶段以及特征模式判断。在此基础上，讨论了对长三角管理的启示。