Transition Indices of Sediment-Transport Modes on a Debris Flow Resulting from Changing Streambed Gradients
Transition Indices of Sediment-Transport Modes on a Debris Flow Resulting from Changing Streambed Gradients
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DOI：
10.3390/w14111810
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发表时间：
2022-06
期刊：
影响因子：
3.4
通讯作者：
Takashi Wada;Hirotada Mishima;Jin Takemura;Kazuki Kobayashi;H. Miwa
中科院分区：
文献类型：
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作者：
Takashi Wada;Hirotada Mishima;Jin Takemura;Kazuki Kobayashi;H. Miwa
我们进行了实验，使用实验水槽与两个变量河床梯度在上游和下游的部分与各种泥石流，组成的大小，和供应流量。根据泥石流下游前缘的输沙浓度、流深和砾石运移速度的测量结果，计算了输沙模式转换指数IC <$x、Ih <$x和IU <$x，研究了从坡度变化点沿着纵向距离的输沙模式转换过程。利用这些指标，我们假设，泥石流通过梯度变化点后，泥沙输运模式的过渡进展，通过改变测量参数的稳定状态下的下游部分的梯度条件。此外，这些指标表明，砾石迁移速度在流动前沿内部的变化最快后，通过梯度变化点，和流动深度往往变化最慢。最后，这些指标表明，随着泥石流物质变得更细，供应流量变得更大，纵向过渡段往往是更长的，因为需要传输的物质的动量小于总的泥石流动量。
We conducted experiments using an experimental flume with two variable streambed gradients in the upstream and downstream parts with various debris flows, composition sizes, and supply flow rates. We investigated the transition processes of sediment transport modes along the longitudinal distances from the gradient change point using the transition mode indices, ICs¯x, Ih¯x, and IU¯x; these indices were calculated based on measurements of sediment transport concentrations, flow depths, and gravel migration velocities in the debris flow’s front in the downstream part. Using these indices, we postulated that after the debris flow passed the gradient change point, the transition of the sediment transport modes progressed by changing the measured parameters to those in the steady-state condition on the gradient of the downstream parts. In addition, these indices suggested that the gravel migration velocities in the flow front interior changed most rapidly after passing the gradient change point, and that flow depths tended to change most slowly. Finally, the indices suggested that as the debris flow material became finer and the supplied flow rates became larger, the longitudinal transition sections tended to be longer because the momentum needed to transport the material was less than the total debris flow momentum.