Centre: River dredging not viable solution for floods

252.6 sq km bank erosion and 118.6 sq km deposition in the Brahmaputra between 2003-05 and 2008-11: CWC

Staff Reporter

Guwahati: Every year, when floods hit the state, there's a renewed demand for dredging the Brahmaputra river, the primary river that cuts across the state, but the central government does not regard dredging or desilting of rivers as 'a technically viable solution for flood control' as it can only 'marginally minimize the magnitude of floods' and is effective only for a 'short period'.

Last year, in the month of July, the Ministry of Jal Shakti submitted before the Lok Sabha a report on 'soil erosion due to floods in Assam'. In the report, it was stated that dredging is not a permanent solution and is only effective for a short-term reduction in the magnitude of floods. It was estimated that a total erosion of 252.6 sq. km. and deposition of 118.6 sq. km. occurred in the Brahmaputra river within two periods of time spanning a few years each.

The report by the Ministry of Jal Shakti said, "Dredging or desilting of rivers is not considered a technically viable solution for flood control as it can marginally minimize the magnitude of floods and is effective only for a short period. Selective dredging in specific reaches such as tidal rivers, confluence points with narrow constrictions, etc. sometimes may have to be undertaken based upon local site conditions; however, the same should be backed by proper scientific study."

Moreover, the Ministry of Jal Shakti has formulated a "National Framework for Sediment Management (October 2022)" for managing sediments in a holistic manner. This framework places emphasis on sediment management through an integrated river basin management plan.

It was also emphasized that the Government of India has been making continuous efforts to assist the state governments in effective flood management and erosion control. Morphological studies using remote sensing techniques by various IITs and the NIIT have been carried out for major rivers, including the Brahmaputra river. These studies play an important role in understanding the nature of rivers in a comprehensive manner and provide an assessment of decadal bank-line movement, erosion, and deposition in different reaches with respect to the base year, the derivation of reach-wise morphological indices, and the identification of critical reaches. These studies have been shared with concerned state governments and other stakeholders, etc., for taking informed decisions and future planning.

As per the morphological study of the Brahmaputra river conducted by the Central Water Commission (CWC) through consultancy from IIT Guwahati, it has been estimated that in the Brahmaputra river, a total erosion of 252.6 sq. km. and deposition of 118.6 sq. km. occurred between 2003-05 and 2008-11.

It was informed by the Water Resources Department, Government of Assam, that around 1,170 bank protection works with geo-materials, concrete slabs or blocks, boulders, etc. have been implemented in order to check the soil erosion in the rivers and rivulets caused by heavy rains and consequential floods in the lower lying areas of the state.

Also read: Assam: 21 districts of state still under grip of floods; one dies in Dhemaji (sentinelassam.com)

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