Multi-channel patterns of bedrock rivers: An example from the central Narmada basin, India
Multi-channel patterns of bedrock rivers: An example from the central Narmada basin, India
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基岩河流的多河道格局：以印度讷尔默达盆地中部为例
DOI：
10.1016/0341-8162(95)00035-6
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发表时间：
1996
期刊：
影响因子：
6.2
通讯作者：
Sheila Mishra
中科院分区：
文献类型：
--
作者：
V. Kale;V. Baker;Sheila Mishra
一个异常的多通道模式在基岩上观察到的纳尔默达河的主要下切达到。多河道河段（宽800 - 2750 m，长8500 m）以主要断层为界，下伏花岗岩和片麻岩基岩。地貌调查揭示了多通道研究区的上、中、下游子河段之间的差异。上游支流以深水流和细泥沙为主，下游支流以陡坡度和急流为特征。中部支流是最宽的，以茂密的森林岛屿和巨石护堤为标志。三个不同的子河段的特点表明，控制岩性，洪水过程和构造的相互作用。对Hack（1973）河流梯度指数值的估算表明，SL值沿Narmada河沿着有相当大的变化。梯度指数的最高值（SL = 797）与多河道河段有关，暗示岩性或构造控制。考虑到河段及其河道的尺寸，目前的水文状况似乎不足以形成该特征。我们假设基岩中的多通道模式的发展是由块体或穹隆隆起。增强的坡度和极端的洪水使该系统能够利用基岩中的线性弱点，导致分支的发展和基岩中多个通道的建立。在研究现场的渠道平面形态和形态的突然变化表明，河流正在调整其渠道几何形状（宽度，深度，坡度和平面配置），通过这种河流环境的极端洪水特性的作用，一个新的平衡渠道形态。
An anomalous multiple channel pattern in bedrock is observed on a predominantly downcutting reach of the Narmada River. The multi-channel reach (800–2750 m in width and 8500 m in length) is bounded by major faults, and is underlain by granite and gneiss bedrock. Geomorphological investigations reveal differences among the upstream, middle and downstream sub-reaches of the multi-channel study area. Whereas the upstream sub-reach is dominated by deep flows and fine sediments, the lower sub-reach is characterized by a steep gradient and rapids. The middle sub-reach is the widest, and is marked by thickly forested islands and boulder berms. The characteristics of the three different sub-reaches suggest control by the interactions of lithology, flood processes and tectonics. Estimations of Hack's (1973) stream-gradient index values indicate considerable variations for the SL values along the length of Narmada River. The highest value of gradient index (SL = 797) is associated with the multi-channel reach, implying lithologic or tectonic control. Given the dimensions of the reach and its channels, it appears that the present hydrological regime is inadequate to produce the feature. We hypothesize that the multi-channel pattern development in bedrock was initiated by block or domal uplift. Enhanced gradients and extreme floods permitted the system to exploit linear weaknesses in the bedrock, leading to the development of anabranches and establishment of multiple channels in bedrock. Abrupt changes in the channel planform and morphology at the study site indicate that the river is adjusting its channel geometry (width, depth, gradient and plan configuration) to a new equilibrium channel morphology through the action of the extreme floods characteristic of this fluvial environment.