Sectoral Migration of Ganga River and Its Implication on the Stability of Phaphamau Bridge Near Allahabad, U.P., India

Comparative examination of Survey of India Topographical Map sheets of 1972–1973 survey and satellite data of 1999, 2006, 2007, 2008 and 2017 period has revealed that the niche point of Ganga river has shifted about 2.9 km upstream (westward) from immediate west of Faizullahpur (in 1973) to the south of Rangpura (by 2017). The sectoral migration of the Ganga channel in Jahangirwa–Phaphamau–Faizullahpur–Jhusi sector has been characterised by oscillations and conspicuous westerly shift in Phaphamau–Faizullahpur segment. The channel oscillation has been very pronounced between 2008 and 2017. The relict channels in the immediate west (upstream) of Phaphamau bridge are evidences of the new pathway carved out by Ganga River during the recent years and may again serve as easy pathways for flood waters during heavy precipitation in the catchment area of the river. Digital Elevation Model of the study area highlights the conspicuous oscillations (of Ganga River) and consequent successive migration within the river valley. The oscillatory migration of the Ganga channel makes its future path very unpredictable and this is turn poses potential risk not only to both the northern and southern bank abutments (of the Phaphamau bridge) but also to the northern and eastern parts of the holy city of Allahabad. In view of this additional protection work is required in the upstream of Phaphamau bridge and also in Phaphamau–Jhusi stretch in the downstream.