Downstream changes in channel morphology and flow over the ephemeral Dwarkeswar River in the western part of the Bengal Basin, eastren India were investigated. The river stretches from the Proterozoic Granite Gneiss Complex to the recent Holocene alluvium, forming three distinctive geomorphological regions across the river basin: the pediplane and upper and lower alluvial areas. Sixty cross-sections from throughout the main trunk stream were surveyed and the bankfull width, depth, cross-sectional area, and maximum depth were measured. Sediment samples from each location were studied and the flow velocity, stream power, Manning’s roughness coefficient, and shear stress were estimated. The results show that the bankfull channel cross-section area, width, width-to-depth ratio, and channel capacity increased between the beginning and middle of the river. Thereafter, the size of the river started to decrease in the lower alluvial area. This was characterized by gentle gradients, cohesive bank materials with grass cover, and channel switching. Within the lower part of the river, the channel capacity was observed to diminish as the drainage area increased. This increased the bankfull flow frequency and accelerated large floodwater losses in the floodplain via overbank flows and floodways.

中文翻译：

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以季风为主的孟加拉盆地河流下游渠道容量减少：以印度东部德瓦克斯瓦尔河为例

研究了印度东部孟加拉盆地西部短暂的 Dwarkeswar 河下游河道形态和流量的变化。这条河从元古界花岗岩片麻岩杂岩体一直延伸到最近的全新世冲积层，在整个流域形成了三个独特的地貌区域：足面和上下冲积​​区。对来自整个主干流的 60 个横截面进行了调查，并测量了岸边宽度、深度、横截面积和最大深度。研究了来自每个位置的沉积物样本，并估计了流速、水流功率、曼宁粗糙度系数和剪切应力。结果表明，满岸通道截面积、宽度、宽深比、河道起点和中部之间的航道容量增加。此后，河流在下冲积区的规模开始减小。其特点是缓和的梯度、带有草覆盖的粘性堤岸材料和通道切换。在河流的下部，观察到渠道容量随着流域面积的增加而减少。这增加了河岸流的频率，并加速了洪泛区通过河岸流和泄洪道的大量洪水损失。