Displacement and transport of marked pebbles, cobbles and boulders during floods in a steep mountain stream
Displacement and transport of marked pebbles, cobbles and boulders during floods in a steep mountain stream
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洪水期间陡峭山涧中标记的卵石、鹅卵石和巨石的移位和运输
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发表时间：
2004
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通讯作者：
M. A. Lenzi
中科院分区：
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作者：
M. A. Lenzi
在白云石山脉的一个小型实验流域（Rio Cordon，5 平方公里）中，对各种大小的床物质颗粒的运动进行了现场观察。在 1993-1994 年和 1996-1998 年期间的个别融雪和洪水事件中，沿河床测量了 860 个标记的鹅卵石、鹅卵石和巨石 (0·032 < D < 0·512 m) 的位移长度。洪水分为两类。第一种包括“普通”事件，其特点是峰值流量重现期为 1-5 年，每小时床载量不超过 20 m3 h−1。第二个是指重现期为50-60年的“特殊”事件。后一种类型的洪水发生于 1994 年 9 月 14 日，峰值流量为 10·4 m3 s−1，平均每小时底泥率为 324 m3 h−1。总位移长度 Li 根据颗粒尺寸的变化取决于床表面各个部分的移动程度：对于较小的、完全移动的颗粒尺寸，Li 与 Di 无关，而对于处于部分传输状态的较大部分，Li 与 Di 一起快速减小。在没有上游沉积物供应的情况下，持续的选择性运输导致通过从床表面逐步风选较细的物质而形成稳定的粗糙装甲表面。由于运输的供应条件不受限制，极端事件的发生和一系列“普通”洪水的持续时间对于河床各个部分的动员程度都起着重要作用。版权所有 © 2004 约翰·威利父子有限公司
In a small experimental catchment of the Dolomites (Rio Cordon, 5 km2) field observations have been carried out on the movement of various sized bed material particles. Displacement length of 860 marked pebbles, cobbles and boulders (0·032 < D < 0·512 m) has been measured along the river bed during individual snowmelt and flood events in the periods 1993–1994 and 1996–1998. Floods were grouped into two categories. The first includes ‘ordinary’ events, which are characterized by peak discharges with a return period of 1–5 years and by an hourly bedload rate not exceeding 20 m3 h−1. The second refers to ‘exceptional’ events with a return period of 50–60 years. A flood of this latter type occurred on 14 September 1994, with a peak discharge of 10·4 m3 s−1 and average hourly bedload rate of 324 m3 h−1. The variation according to grain size of total displacement length Li depends on the degree of mobilization of the individual fractions of the bed surface: Li is independent of Di for smaller, fully mobile grain sizes and decreases rapidly with Di for larger fractions in a state of partial transport. Sustained selective transport without a supply of sediment from upstream leads to the development of a stable coarse armoured surface through progressive winnowing of finer material from the bed surface. With supply unlimited conditions for transport, both the occurrence of extreme events and the duration of a sequences of ‘ordinary’ floods play an important role in the degree of mobilization of the individual fractions of the bed. Copyright © 2004 John Wiley & Sons, Ltd.