The Ganga Morphology - The Ganga: Water Use in the Indian Subcontinent - page 52

local people started cultivating on it. It remained blocked, round the year, for over
2 km on the left and only a thin course flowed further down. It reduced the sudden
flow concentration on the right bank, near Dhulian town which might have helped
reduce the erosion near it and Aurangabad town afterward.
As the left channel was blocked, the flow enhanced on the right channel by cre-
ating cross, or parallel, flows downstream, from the left to the right, which created
deep scour-holes in the bed and threatened to move toward the barrage. This was
prevented by dumping stones etc. at a huge cost up to 1988, which stabilised the
holes. The submerged bed-bars, constructed later, slowed down the formation of a
cross-flow and pushed it to hit the char and arrested its advance toward the bar-
rage. As a result, the flow got more passage below to join the right-side secondary
channel. This eventually became the only channel below the barrage. Afterward
for holding the entire flow, very high floods, above 50,000 cumecs occurred, com-
pletely submerging the char and distributing it over the entire width of the river.
The huge concentration during both rising and falling floods started eroding the
right bank, just below the barrage in villages like Beniagram, Bindugram, Jaffarganj,
Nayansukh very critically from 1983, or so and orchards, mango groves, farmland
etc were engulfed. Bank revetment and other protective measures were taken by the
barrage authority and the State irrigation department at very high cost to control
erosion up to Dhulian town but it was quite severe from 1984 to 1990 and again
in 1995. Of the 20 km reach from Farakka to Dhulian about 10 km could be pro-
tected up to 1995 and erosion controlled. Work on the remaining portion was done
in phases but about 150-300 m wide land was washed away.
Had the left channel been kept active after commissioning the barrage by
properly regulating the barrage gates and artificial dredging, the flow could be main-
tained and erosion on the right bank minimised. The bed-bars below, at different
bays required regular maintenance and extension. The deep channel is still very
close to the right bank but meandered to the left, below Dhulian. It being almost
straight up to Dhulian with a few local bends, it would not have been difficult to
prevent, or reduce, serious erosion in this reach owing to excessive flow concen-
tration and weak bank. Properly designed revetment by small bed-bars could hold
the bank-line and keep the channel away from it. Any other technique for holding
the bank-line, i.e. by long spurs might have helped divert the main flow toward the
parent river but this would have definitely aggravate erosion, further down, at new
Dhulian town, or below. The deep channel which shifted left, through another mean-
der bend, would be disturbed because of upstream encroachment by spurs, making it
shift to the right again, which would be disastrous and may restart erosion. The mor-
phology of the alluvial channel which takes pretty long to attain dynamic stability
would be disturbed again.
Other erosion zones further down, on the right bank, at Geria, just above the
Bhagirathi offtake, Raghunathpur, Kutubpur etc. downstream, could be controlled
by protective measures. Two channels united below Kutubpur and the combined
discharge hugged the right bank, causing severe erosion. Farmland and villages were
affected and very costly protective measures are now under way to protect them.