Observations of Bed Load Transport and Channel Bed Changes in a Proglacial Mountain Stream
Observations of Bed Load Transport and Channel Bed Changes in a Proglacial Mountain Stream
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冰川前山溪流中床荷输送和河道床变化的观测
DOI：
10.2307/1551657
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
J. Warburton
中科院分区：
文献类型：
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作者：
J. Warburton
1987年5月至7月期间，在Bas Glacier d 'Arolla，瑞士的冰前流的推移质输运和通道变化进行了测量。在几个小时的采样期间，推移质输运的变化显示出与流量没有明显的关系，但是，在67天的研究期间，横截面和长剖面调查表明，稳态运输保持，除了在洪水期间。推移质输移发生在约三分之二的河道宽度上，但大部分推移质是在宽度较窄的带中输移的，与最大水流线松散地对应。在狭窄的地带推移质运动的原因，运输率变化高达1米的空间内（在跨通道方向）的数量级。推移质取样误差大，很难估计输沙过程的真实变化。在低到中等流量期间，河道泥沙储量的短期每日变化很小，但在洪水期间，河道从轻微加积状态急剧转变为相当加积或退化的状态。本文在野外观测和泥沙输移测量的基础上，提出了一个适用于河床物质高度不均匀的陡粗床河流的推移质输移三相模型。第一阶段通常涉及在低流量期间冲刷沉积在通道中的细粉;第二阶段运输与砾石床表层的破碎有关;第三阶段运输导致洪水期间台阶/水池地形的破坏。
Bed load transport and channel change were measured during May to July 1987 in the proglacial stream of Bas Glacier d'Arolla, Switzerland. Over sampling periods of several hours, variations in bed load transport show little apparent relationship with discharge; however, over the 67-d study period, cross section and long profile surveys suggest that steady-state transport is maintained, except during floods. Bed load transport occurs over approximately two-thirds of the channel width, but the majority of the load is transported in bands of narrow width corresponding loosely to the maximum thread of flow. Bed load movement in narrow bands causes transport rates to vary by up to an order of magnitude within the space of 1 m (in a cross channel direction). Large errors associated with bed load sampling make it very difficult to estimate the true variability in the sediment transport process. Short-term daily changes in channel sediment storage are minor during periods of low to moderate discharge, but during floods the channel shifts dramatically from a slightly aggrading state to a state of considerable aggradation or degradation. On the basis of field observations and sediment transport measurements, a three-phase model of bed load transport is proposed for steep coarse-bed streams where bed material is highly heterogeneous. Phase one generally involves the flushing out of fines deposited in the channel during low flows; phase two transport is associated with the break-up of the gravel-bed surface layer; and phase three transport results in the destruction of the step/pool topography during flood.