The Ganga Morphology - The Ganga: Water Use in the Indian Subcontinent - page 53

The meander bend on the right bank continued up to Akhriganj in Murshidabad
before the river finally enters Bangladesh. This deep channel which is very active
on the right bank caused severe erosion near Akhriganj and Jalangi bazar area for
about 8 km since 1930, engulfing over 350 m wide land. In 1989 erosion here was
more severe and a large landmass, including school, market and other buildings went
into the river. Erosion continued up to 1995 and in spite of spending huge amounts
by the State government to check erosion could not be totally stopped. Long spurs
constructed in 1990 were severely outflanked. Erosion below the spurs increased,
affecting civil structures and farm land.
The Bhagirathi-Hooghly became moribund in its upper reach in pre-barrage days.
It used to be active only in monsoon months, when activities on it reduced and its
silted mouth was over-flooded by the high Ganga level and again from October, or
so, the flow decreased, rendering the river a stagnant pool. As there was practically
no flow from November to June, there was no bank erosion in the upper reaches
in those months except in monsoon months. Slips only occurred at some places
owing to the drawdown state of the ground-water table. In the lower reach in the
Bhagirathi and the Hooghly the condition was different, as it was a mature and active
reach because of flows from the tributaries and the tides from the sea. Therefore,
these reaches suffered bank erosion, round the year, which aggravated in monsoon
months. After induction of upland discharge through the Feeder Canal, the joint
river remains active throughout the year, regaining its life. This rejuvenation gave
rise to erosion in many reaches, which is particularly severe in meander bends but
less in braided and straight reaches. The most vulnerable erosion zones of the river,
as revealed by the survey data of 1985-1986 are shown in Table 5.1.
The Table 5.1 shows that in 1985-1986, there were 26 major erosion-prone zones
in the Bhagirathi-Hooghly. The first 16 were in the Bhagirathi and the last nine
in the Hooghly. The approximate affected length and the nature of land loss are
indicated in the table. Mostly farm land, villages and industries were affected. The
total affected length on the left bank was about 40 km and about 45 km on the
right bank, out of the total length of the joint river of 425 km from the offtake
in Murshidabad to Falta in south 24-Parganas district. In many of these affected
reaches, the river has been engulfing farm land, almost every year. The shift of
bank line in four major reaches (two in each) - Purbasthali and Mayapur on left
bank and Samudragarh and Zirat on right bank from 1976 to 1987 are shown in
Table 5.2.
The continuous encroachment by the river on the land by the Mayapur reach
from 1976 to 1987 is shown in Fig. 5.9 below. On the left bank stands the famous
Vaishnaba temple and the headquarter of the ISCON and on the right the legendary
Nabadweep town, abounding in Vaishnava temples and controversial birth place
of Shri Chaitanya Dev, founder of the Hindu sect. It is also near the outfall of
the Jalangi, a tributary of the Ganga. Over a million square metre of land went
under water between 1976 and 1987; the old temple is now threatened. All the four
reaches, as shown in Table 5.2, are within the meander loops. Erosion is severe on
the concave side of the bend with alluvial fans formed on the opposite face. A study
of erosion of the joint river in 1985-1986 showed that the annual erosion in the