The Ganga Morphology - The Ganga: Water Use in the Indian Subcontinent - page 51

Photograph 5.3 Flood affected people taking shelter over marginal embankment (See also Plate 3
on page 367 in the Colour Plate Section)
1971 floods, deep scours developed just below the closed bays, which meant that
the main channel still remained on the left half of the barrage, downstream. These
developments implied that the erosion of Dhulian and Aurangabad was not due to
the construction of the barrage but to the joining of the two channels in the location,
severely concentrating the flow.
Even before the formal opening of the barrage, in 1975, its gates were partly
operated to regulate and pass the full flood discharge, downstream. The river's mor-
phology began to change because of the barriers since 1970. The downstream shoal
(alluvial fan) inside which was away from the barrage by about 2 km in 1960 moved
toward it owing to the changed flow and silt deposition and finally reached within
500 m by 1980. The left active channel gradually shrank owing to the obstruction.
The deep channel which was shifting leftward to the barrage with the flow stopped.
The primary consideration for regulating the barrage gate was to keep the channel
on the right, upstream so as to draw required silt-free water into the Feeder Canal.
To achieve this, the right bays were kept open more during rising and falling floods.
The cross current, or parallel flow, which developed in initial years of operation
from right to left in front of the barrage was prevented by protecting scour holes and
by constructing the submerged bed-bars at various bays, both below and above the
barrage. Moreover, as the passage of water was blocked, the flow hit the land adja-
cent to the right guide bund and eroded it. The protective works of the bund were
affected and had to be maintained at great cost. All these along with the throttling
of the barrage gates, more on the left side, increased the siltation of the left channel
below, which slowly dried up by 1983, or so and the mid-river char extended and
joined the left bank. This way, the left channel below was completely blocked and