The mighty Brahmaputra has wiped out nearly 4,000 square kilometres of area at a rate of 80 square kilometres per year, destroying more than 2500 villages and affecting more than five million people in Assam.Assam’s Water Resources Department has identified 25 vulnerable and very severe erosion-prone sites and estimated that the Assam valley portion of the Brahmaputra has lost approximately 7.4 per cent of its land area due to river bank erosion and channel migration.
The Committee for Developing Mitigation Strategies for Brahmaputra River Basin Flood and Erosion Problem a joined committee comprising experts from Assam and the USA, have come forward with a set of short and long term measures to address the problem and develop cost-effective solutions.
The experts have pointed out that the key factors in causing the river extremely unstable at many reaches are ’aggradation’ (raising of the river bed due to sediment deposition), intense ‘braiding’ and large water discharge.
They pointed out that till now both short and long term measures to tackle the erosion problem had been done only on a piecemeal basis during emergency situations depending on availability of funds.
Experts in the committee are: Retired professor of civil engineering, University of Alaska, Dr Arvind Phukan, senior project manager at Woolpert, Virginia, Deva Borah, chairman of the Surface Water Hydrology Committee of the American Society of Civil Engineers Ananta Nath, Assam Water Resources Department’s senior engineer Rajib Goswami and professor of civil engineering in IIT, Guwahati, Chandan Mahanta.
They have recommended phase-wise solution for the mitigation of erosion by including a combination of measures including strategic dredging, protection of erodible bank materials with anchored bulkhead or tie back sheet piles, spurs, toe and bank revetments.
Improvement of data quality and quantity by extending rain, flow and sediment monitoring network using state-of-the-art equipment and consider physical modelling to study severe and potential scour sites and their control have also been suggested by the experts.
The experts further recommended development of advanced and efficient computational tools capable of utilizing the detailed hydro-meterological data and predicting real-time flooding and hydraulic characteristics of the river for planning and designing effective flood and erosion control measures.
The committee has suggested taking advantage of modern technologies such as satellite image-based morphological study, studying of successful erosion control measures in major rivers of the world and feedback from international experts among steps to stem the erosion in the Brahmaputra at the earliest.
The committee suggested strengthening and monitoring of anti-erosion measures already taken up at Majuli Island and severely eroded towns along the river and armouring existing embankments located at urban and other strategic locations.
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