The present research based on 39 cross sections, historical maps, satellite images, and intensive field investigations intends to portray the changes in the cross-sectional morphology and channel efficiency of the lower Bhagirathi River (Katwa to Nabadwip) after the Farakka barrage was constructed over the Ganga River in 1975. The study reveals that majority of the cross sections have undergone significant changes in terms of higher width/depth ratio (1972:71.4 and 1984:85.1), higher channel form index (1972:28.06, 1984:33.44), and higher areal asymmetry (1972:0.244, 1984:0.287). Thus, discriminant analysis based on the principal component analysis Z-score of the derived indices shows a reversal of the quadrant reflecting a definite change in cross-sectional morphology in the post-Farakka barrage condition. Though the Reynolds number and specific stream power increased due to the increase in the lean period (January to May) discharges by the controlled hydrology, channel efficiency has decreased which is reflected through the higher Chezy roughness factor (1972:0.095 and 1984: 6.802) and increasing braiding index (1994:0.103, 2019:0.294). This is due to the emergence of the transport-limited condition triggered by the inadequate discharge compared to the huge sediment load contributed by Bhagirathi bank erosion and the Ajay–Mayurakshi system. Moreover, the role of erosion permitting sand and silt facies triggering higher channel oscillation along the left bank and presence of plug bar deposits coupled with the suspected attraction of subsurface fault are also noted on the relative stability and channel orientation of the middle part of the study reach.

本研究基于39个断面，历史地图，卫星图像和密集的现场调查，旨在描绘在法拉卡河拦河坝建成后，下游Bhagirathi河（Katwa至Nabadwip）的断面形态和河道效率的变化。 1975年的恒河。研究表明，大部分断面在较高的宽深比（1972：71.4和1984：85.1），较高的河道形态指数（1972：28.06、1984：33.44）方面发生了显着变化。 ，以及更高的面积不对称性（1972：0.244，1984：0.287）。因此，基于主成分分析Z的判别分析衍生指数的-score显示象限的倒转，反映了法拉卡后弹幕状态下断面形态的确定变化。尽管由于水文控制期间稀水期（1月至5月）的排放量增加，雷诺数和比流功率有所增加，但渠道效率却有所下降，这反映在较高的化学粗糙度因子上（1972：0.095和1984：6.802）并增加编织指数（1994：0.103，2019：0.294）。这是由于与Bhagirathi河岸侵蚀和Ajay–Mayurakshi系统造成的巨大沉积物负荷相比，由于排放不足引起的运输受限条件的出现。此外，