TURNING THE
BRAHMAPUTRA TIDE – THE RAHMORIA EXPERIMENT
Akshey
Kumar*
Himank
Kothiyal**
For the people
of Rahmoria in Dibrugarh district of Assam, the place has lived
up to its name – literally, as the villagers have turned the tide
against the floods, which had been plaguing the place every year,
rendering the people homeless. But this year, despite the heavy
monsoons, the people here have been spared the vagaries of floods.
It is not that the mighty Brahmaputra river is quiet, or without
water. But thanks to a pilot project undertaken by the Brahmaputra
Board as a part of the Prime Minister’s initiative for the North-East,
the flow of the Dibang river, a tributary of the Brahmaputra,
has been diverted and the villages have been saved from the annual
destructive cycle, particularly in the reach from Saikhowaghat
to Dibrugarh and mainly in Hatighuli and Rahmoria villages.
Cause
As the experts
examined the phenomenon, it became evident that floods in this
area were due to the southward thrust of the Brahmaputra caused
by the Dibang river, which flows from north to south, confluencing
with the combined flow of the Lohit and Noa-Dehing rivers at Dholla-Hatighuli.
Since 1992 a small man-made channel known as Anant nalla developed
into a mainstream of the river Brahmaputra near Hatighuli. In
1998-99 it was observed that more than half of the total discharge
of the river Brahmaputra was passing through the Anant nalla.
Subsequently, a new channel known as Ballu nalla also developed
about 300 metres upstream and south of Anantanalla. This resulted
in heavy erosion from Dholla to Dibrugarh all along the south
bank and the worst affected area was Rahmoria, which is situated
downstream of the river Dholla.
The situation
reached such an extreme that in June 1998 about 450 metres of
Saikhowa, a protection bund, was eroded and the flood caused havoc
in the adjoining nine villages at Hatighuli.
Initiative
When the Prime
Minister, Shri Atal Bihari Vajpayee, visited Dibrugarh on April
2, 2002, the people of Rahmoria and the adjoining areas made a
representation urging him to initiate actions to mitigate the
flood problems of that area. As a follow-up action, the Brahmaputra
Board under the Ministry of Water Resources, Govrenment of India
was entrusted with the task of forcibly separating the river Brahmaputra
near Dholla-Hatighuli.
Changing The
Course
After a detailed
study of the river configuration, the Brahmaputra Board took up
the diversion of the river Dibang at Dholla from its north-south
course to a course parallel to the flow direction of the Lohit
and thus reduce the pressure on the Lohit river at Hatighuli.
It was decided that only the locally available material like bamboos
and wood will be used instead of costly techniques.
The first phase
of the work was taken up in January, 2003 and completed in mid-April
at a cost of Rs.6.5 crore. The flow of water was adequately controlled.
Pro-Siltation:
The Method
The re-inforced
concrete RCC porcupines were interspersed with bamboo porcupines
to reduce the cost. The turfing work was also initiated alongside
the bundhs. All this resulted in checking the soil erosion. As
a result, the overflow of water this year, instead of causing
any further erosion has in fact, reversed the process. It has
been found that the porcupines across the Dibang river have induced
heavy siltation to an average depth of 3 metres. It was also observed
that 80 per cent of the flow of the Dibang river has been diverted
through a channel, upstream of the porcupines, flowing in an east-west
direction, as planned. On the other hand, there was heavy erosion
in the north bank of the new channel indicating increased flow.
All this has resulted in reduced pressure on the flow of the Lohit
river along its south bank. Consequently, there was no flood havoc
in more than 14 villages this year in Hatighuli and the entire
bundh constructed by the Board from Dholla to Hathiguli and to
Rahmoria did not experience any severe flood and remained intact
. This has also reduced the water pressure in the Rahmoria area
for the first time in the last two decades, minimizing the erosion.
The project’s
success has further raised the hopes of the local people and the
Brahmputra Board now proposes to take up similar pro-siltation
measures across the Ananat nalla and Balu nalla to divert the
river Lohit to its original course which is north of Anant nalla,
as Phase-II for Avulsion of Brahmputra at Dholla Hatighuli during
the next winter.(PIB Features)
*Director
Public Relations, PIB, New Delhi
**Assistant
Information Officer,PIB, New Delhi
