Effect of Sediment Supply on Morphodynamics of Free Alternate Bars: Insights from Hydrograph Boundary Layer
Effect of Sediment Supply on Morphodynamics of Free Alternate Bars: Insights from Hydrograph Boundary Layer
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DOI：
10.3390/w13233437
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发表时间：
2021-12
期刊：
影响因子：
3.4
通讯作者：
H. Dai;T. Iwasaki;Y. Shimizu
中科院分区：
文献类型：
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作者：
H. Dai;T. Iwasaki;Y. Shimizu
泥沙供给在河流形态方面起着至关重要的作用。然而，泥沙供给对河流形态的具体影响并不明显。根据水文边界层（HBL）概念，由泥沙供给和输沙能力之间的不平衡所导致的上游河床变化只能传播有限的长度，并且对超出此短距离的河床影响可忽略不计。我们进行了二维地貌动力学计算以检验在一维模拟下提出的HBL概念，这意味着HBL概念对于河流形态的平面变化仍然有效。我们在一个具有不可侵蚀河岸的直的、模拟的砾石河床河道中采用具有平衡或恒定泥沙供给的非恒定流来模拟交错边滩地貌动力学。结果表明，无论泥沙供给条件如何，在HBL下游形成的交错边滩特征都非常相似。这表明上游端的泥沙扰动对包括HBL下游交错边滩形成和发展在内的动床动力学过程影响可忽略不计。
Sediment supply plays an essential role in river morphology. However, the specific impact of sediment supply on river morphology is not apparent. According to the hydrograph boundary layer (HBL) concept, upstream riverbed changes caused by the imbalance between sediment supply and the capacity can propagate only a limited length and have a negligible effect on the riverbed beyond such a short length. We performed a two-dimensional morphodynamic calculation to test the concept of HBL, which was proposed under a one-dimensional simulation, meaning that the concept of HBL is still valid for plane changes in river morphology. We employed an unsteady flow with equilibrium or constant sediment supply in a straight, modeled gravel-bedded channel with an unerodible bank to simulate alternate bar morphodynamics. The results show that regardless of the sediment supply condition, the alternate bar features formed downstream of the HBL are considerably similar. This suggests that sediment disturbance at the upstream end has a negligible effect on the mobile-bed dynamic processes, including alternate bar formation and development downstream of the HBL.