The Ganga Morphology - The Ganga: Water Use in the Indian Subcontinent - page 40

mobile and gradually-shifting point-bars at many places, mid-stream. The swinging
river changed the channel by braiding and meandering, alternatively. One such
point-bar developed upstream of the barrage on the right and is increasing in length,
breadth and depth. This extension upstream is engulfing the mouth of the Feeder
Canal at the Lock Channel entrance and causing the right channel shrink and stag-
nate as well as to erode the bank on the left. The growth of this bar left many
long-term adverse effects and if unchecked along with other ill effects upstream
of the barrage, may jeopardise its basic purpose. The morphological changes will
continue to occur until the river adjusts to the changed conditions.
Downstream, on the left, there was a big alluvial fan which, moving up gradually
before the construction of the Farakka Barrage, resulting flow concentration on the
right and with the deep channel passing close to the right bank, eroded it. The fan
extended up to about 30 km below Farakka; old Dhulian and Aurangabad towns
on the right were also severely eroded. Moreover, the entire area was affected by
occasional floods in monsoon months. After the barrage came up, the river-bed was
degraded considerably and flood hazards reduced. The advance of the alluvial fan
toward the barrage stopped. The left-side stream which existed before the barrage
silted, leaving no trace of the channel. The fan is shrinking because of erosion of
its right face, though reduced, following controlled discharge through the barrage,
erosion has not stopped altogether and encroached land, necessitating very costly
protective measures (Fig. 5.4).
Below Aurangabad - 20 km downstream - the river has two distinct channels,
separated by a big point-bar, i.e., char land. Discharge through the right channel has
reduced, giving more water way to the left which is very near Bangladesh border.
There is very little habitation in the flood-plain, called khadir , in local parlance. The
channel in the entire reach up to Jangipur, some 30 km, is mostly braided because
of local meander zones up to the Bhagirathi off-take. The point-bars and alluvial
fans are low and criss-crossed by channels which are all over-flooded in monsoon
months. Erosion continues on both sides but as the left side is mostly khadir land
and has little habitation, there is no hue and cry over this. The right bank which
is thickly populated faced severe erosion in the 1970s, which afterward could be
checked by protective measures (Fig. 5.5).
Below the off-take, the Bhagirathi flows for another 20 km into Indian terri-
tory and then along the border between the two countries for another 50 km or so.
Here also, the river is predominantly braided with alluvial fans on the left and has
low point-bars, intercepted by shallow channels owing to alluvium deposits. There
were severe erosion on the right bank in the 1970s and 1980s; the right channel
encroached on farm land and villages nearby. The erosion was checked for the first
15 km but further down, it is continuing. The most vulnerable reach where erosion is
on is Akhriganj in Murshidabad where the densely populated area and the old town
are affected occasionally. The left and right side channels have joined here, aggra-
vating the situation. After flowing almost straight up to Lalgola, the river takes a left
turn first and then a right turn above Akhriganj. The pattern changes from braided
to meander before finally entering Bangladesh.