DYNAMICS OF WOOD TRANSPORT IN STREAMS: A FLUME EXPERIMENT
DYNAMICS OF WOOD TRANSPORT IN STREAMS: A FLUME EXPERIMENT
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河流中木材运输的动力学：水槽实验
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
H. Ikeda
中科院分区：
文献类型：
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作者：
C. Braudrick;G. Grant;Y. Ishikawa;H. Ikeda
多年来，木质废弃物对航道形态和水生生物栖息地的影响已经被认识到。然而，与沉积物不同的是，人们对木材如何在河流系统中移动知之甚少。我们通过一系列水槽实验研究了河流中木材运输的一些动态，并观察到三种不同的木材运输模式：非拥堵、拥堵和半拥堵。在不拥堵的运输过程中，原木的移动没有片断的相互作用，通常占用不到10%的航道面积。在拥挤的运输中，原木作为一个整体一起移动，占据了航道面积的33%以上。半拥堵运输介于这两种运输方式之间。运输制度的类型对无量纲输入速率的变化最为敏感，定义为每秒输送到通道的原木体积(Qlog)与排放(QW)的比率；该比率在非拥堵运输的0.015和拥堵运输的0.020之间变化。稳定原木堵塞中的沉积组构因运输类型的不同而不同，来自非拥堵和半拥堵运输模式的沉积组构的正常流向的比例高于来自拥堵运输的沉积。由于低阶通道的木材输入速率更高，通道尺寸相对于块大小而减小，我们预计拥塞的传输将在低阶流中更加常见，而非拥塞的传输将主导较高阶的流。单一浮选模型可以用来模拟单个浮选段的稳定性，特别是在较高阶的河道中，但不足以模拟较低阶河流中出现的更复杂的内部情况。©1997 John Wiley&Sons，Ltd.
The influence of woody debris on channel morphology and aquatic habitat has been recognized for many years. Unlike sediment, however, little is known about how wood moves through river systems. We examined some dynamics of wood transport in streams through a series of flume experiments and observed three distinct wood transport regimes: uncongested, congested and semi-congested. During uncongested transport, logs move without piece-to-piece interactions and generally occupy less than 10 per cent of the channel area. In congested transport, the logs move together as a single mass and occupy more than 33 per cent of the channel area. Semi-congested transport is intermediate between these two transport regimes. The type of transport regime was most sensitive to changes in a dimensionless input rate, defined as the ratio of log volume delivered to the channel per second (Qlog) to discharge (QW); this ratio varied between 0·015 for uncongested transport and 0·20 for congested transport. Depositional fabrics within stable log jams varied by transport type, with deposits derived from uncongested and semi-congested transport regimes having a higher proportion of pieces orientated normal to flow than those from congested transport. Because wood input rates are higher and channel dimensions decrease relative to piece size in low-order channels, we expect congested transport will be more common in low-order streams while uncongested transport will dominate higher-order streams. Single flotation models can be used to model the stability of individual pieces, especially in higher-order channels, but are insufficient for modelling the more complex intractions that occur in lower-order streams. © 1997 John Wiley & Sons, Ltd.