Fluvial processes in a forested anastomosing river: Flood partitioning and changing flow patterns
Fluvial processes in a forested anastomosing river: Flood partitioning and changing flow patterns
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DOI：
10.1002/esp.3290180808
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发表时间：
1993-12
影响因子：
3.3
通讯作者：
K. Harwood;A. Brown
中科院分区：
文献类型：
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作者：
K. Harwood;A. Brown
为了进一步加深我们对多渠道系统的理解，本文提供了欧洲最后一个树木繁茂的半自然吻合系统之一的渠道洪水响应的数据。爱尔兰基拉 (Gearagh) 的特点是有数百个小岛，这些小岛被相互连接的低坡度河道隔开。其中包括与主流成直角穿过岛屿的河道和盲道分支河道。岛屿相对稳定，树木繁茂，有证据表明岛屿因河道侵蚀而分裂，并因河道内沉积而生长。调查了四个活动区域交叉剖面，每个剖面包含 7 到 13 个通道。在两次单独的洪水之前和期间测量了多个渠道的速度。根据这些观察，通道被分为三种类型：快速（浅层和梯形）；缓慢（深且更不规则）；和洪水渠道。洪水期间，由于泥石坝后退，导致水面高程变化，导致河道间流动，这被认为是异常跨岛河道的起源，也是岛屿分裂的原因之一。岛屿分裂的另一个潜在原因，即盲目的分支通道，是根群之间集中河岸冲刷的结果。生物成分如碎片坝、树根群和树木抛坑在水流分隔中发挥着关键作用，并导致河道速度和漫滩速度分布的变化。简要讨论了这些观察结果对通道模式维护的影响。
In an effort to further our understanding of multiple channel systems, this paper presents data on the flood response of channels in one of the last wooded, semi-natural anastomosing systems in Europe. The Gearagh, Ireland, is characterized by hundreds of small islands separated by interconnected channels of low slope. These include channels that cross islands at right angles to the main flow and blind anabranching channels. Islands are relatively stable and wooded, with evidence of division by channel erosion and growth by in-channel sedimentation. Four active zone cross-profiles were surveyed, each containing between seven and 13 channels. Velocities were measured in several channels before and during two separate floods. From these observations channels have been categorised into three types: fast (shallow and trapezoidal); slow (deep and more irregular); and flood channels. During the floods, interchannel flows were caused by variations in water surface elevations due to backing-up behind debris dams, and it is suggested that this is the origin of the anomalous cross-island channels and one cause of island division. Another potential cause of island division, blind anabranching channels, is the result of concentrated bank scour between root masses. Biotic components such as debris dams, tree root masses and tree-throw pits play a key role in the partitioning of flow, and cause variations in channel velocities and the overbank velocity distribution. The implications of these observations for channel pattern maintenance are briefly discussed.