Geoscience Reference
In-Depth Information
Photograph 5.1 Bank erosion near Panchnandapur in Malda district (See also Plate 1 on page 365
in the Colour Plate Section)
the river a dynamic stability. Any further interference by long spurs, diversion
canals etc. may make the river swing leftward and aggravate erosion, which would
require more time for the course to adjust to such changes and stabilise (Fig. 5.8).
Photographs 5.2 and 5.3 show the breach of a portion of the marginal embankment
and people taking shelter over the embankment.
As said, the 1960 survey showed the left channel as more active and larger than
the right channel below Farakka. The right channel along Nayansukh village and
Dhulian town was carrying less than 25% of the flood discharge in those days. It
was observed that though the right channel was narrower than the left, the veloc-
ity of flood water in both was about 3 m/s and the channels were also quiet deep.
This means, the erosion near Nayansukh and Dhulian could be due to the less active
right channel because of increased flow in the narrower but deep secondary chan-
nel, a normal feature. The process continued for years and between 1945 and 1950,
the river eroded about 1 km wide land near Dhulian town. In 1952-1953, erosion
reached its zenith and old Dhulian town gave way. The 1939 survey surmised that
the two bifurcated channels joined just below Dhulian town, where heavy flow con-
centration caused such devastation. The present Dhulian town came up at about
2 km downstream of the old town. Erosion lasted up to 1956 when the gap between
the old and the new town also eroded so extensively from 1950 to 1960 that the
old rail-line between Barharwa and Nimtita (to be precise, between Sankopara and
Loharpur Halt) - a distance of about 13 km - had to be abandoned and a new line
had to be laid away from the river-bank.
During the construction of the barrage, the earthen coffer dam, stretching from
bay 1 to bay 52 on the right bank, was retained inside the river, from 1964 to 1969,
although the sizes of the dam varied in different years. In the first year, the dam
covered first three bays which were retained even in the flood season but in 1969
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