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Dredging the Brahmaputra

Sentinel Digital DeskBy : Sentinel Digital Desk

  |  28 April 2017 12:00 AM GMT

With pre-monsoon showers accompanied by hailstorms already lashing large parts of Assam, there is much anticipation how the rainy season will pan out this year. The Brahmaputra and its 30-odd tributaries are in renewed focus, now that a tripartite pact is in place for dredging the mighty river from Sadiya to Dhubri and onwards to Chittagong port in Bangladesh. However, many other aspects of the agreement are hazy, including its time frame and estimated cost. The question uppermost in the minds of most people here is the ambition and scope of the project — does it aim at erosion and flood control, or does it envisage keeping the Brahmaputra’s main channel vigable, or both? It is true that the British colonialists used to dredge the Brahmaputra bed regularly, but that was only for maintaining regular flows during the lean season to eble ships to ply without hindrance. But the river’s erosion is another matter altogether, a problem so big and complex that it has divided experts for long. The Assam government had officially stated last year that the dredging would primarily focus on ‘erosion control, sediment magement and flood control’, and that the process would be carried keeping in mind the ‘hydrological character’ of the river. Around 8,000 hectares of land in the State has already been lost due to erosion. Even as flows in the Brahmaputra have been declining over the years, siltation has accelerated, resulting in the river expanding to 12 kms near Sadiya and Dibrugarh. The highly braided river flows over a large draige area of 5,73,394 sq km; during floods, it is estimated to transport approximately 13 million tonnes of suspended sediment per day. The agreement between Assam government, the tiol Highways Authority of India (NHAI) and the Inland Waterways of India (IWAI) was signed at the conclusion of the mami Brahmaputra Festival early this month. Basically, the project envisages digging a deep channel on the riverbed and building two express highways along its banks by using the silt and sand dredged up. The idea is that a deeper channel will increase the river’s water retention capacity; once it is confined to a single channel with easy bends, it will desist from cutting its banks. The proposed express highways along the banks are expected to double up as embankments and prevent flooding.

Scooping mud, gravel and sediments from the riverbed is a delicate exercise, so that it does not get disturbed irredeemably. Considering the Brahmaputra’s high sedimentation rate, it is obvious that dredging its bed will have to be continuous process, which in turn will be a regular costly exercise. Experts have suggested supplementary engineering solutions like digging sufficient reservoirs to reduce sediment input, building small dams on tributaries to reduce floodwater flows and afforestation of catchment area in the upper reaches. The Central government has assured Dispur of full cooperation in the project, with Union Road Transport & Highways Minister Nitin Gadkari announcing that Rs 40,000 crore would be released for the construction of Express highways on both banks of the river, each 840 km long, from Sadiya to Dhubri, along with funds for the development of over 50 jetties on the river banks. The Brahmaputra tiol Waterway-II will have direct access to Chittagong port of Bangladesh and Haldia port of West Bengal, is expected to boost trade with Southeast Asian tions, Gadkari said. After completion of prelimiry survey last September, a full scale survey will have to be carried out and completed soon, and it too will have to be a regular process. There have been desultory attempts in the Sixties and the Seventies by Assam governments to dredge small sections of the Brahmaputra, but these came to nought. The full scale project being planned should be long-term and comprehensive, for the futures of lakhs of riverine people in the State will depend on its success. It is important to think big and positive, but both New Delhi and Dispur will need to be more forthcoming about its contours and involve local stakeholders. The importance of social capital and accessing the traditiol knowledge of riverine people should not be missed in this context.

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