Brahmaputra dredging set to be a costly affair
The mighty Brahmaputra River has, from 1920 to 2008, wiped out over 4,000 square kilometres of land area at a rate of 80 sq kms 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% of its land area due to river bank erosion and channel migration. With regard to management of flood and erosion of Brahmaputra-Barak basin, the recommendations of the workshop on thrust for water resources department, which recently concluded, included that it is necessary to specifically identify the source of silt being carried by a river and then to take appropriate sediment management steps, forestation, where found necessary to build silt and flood detention structures and take up any other tasks which would ultimately contribute in a positive way to reduce flood, erosion and undesirable depositions.
The experts opined that it will be appropriate to adopt integrated river basin planning approach for managing the Brahmaputra river system as a norm based upon the principles of Integrated Water Resource Management and geomorphic, hydrologic, hydraulic, sediment transport, topographical and cross-sectional data on priority basis. Following this, the Assam government said it will start dredging of the Brahmaputra River to give people relief from the perennial problem of flood.
According to an official release, chief minister Sarbananda Sonowal held a meeting with officials of the Dredging Corporation of India Limited. “In order to give succour to the people ravaged by perennial floods and erosion, state government with the help of Dredging Corporation of India, will start dredging of Brahmaputra River,” the release mentioned adding that a survey team is likely to visit Assam in 8-10 days to carry out survey work. Based on the findings, an action plan would be prepared for dredging on an annual basis.
Dredging would primarily emphasize on erosion control, sediment management and flood control and the whole process would be carried out in line with the hydrological character of the Brahmaputra, the statement said. However, it remains clouded how dredging is actually carried out.
Dredging is the removal of sediments and debris from the bottom of lakes, rivers, harbours, and other water bodies. It is a routine necessity in waterways around the world because sedimentation - the natural process of sand and silt washing downstream - gradually fills channels and harbours.
Dredging often is focused on maintaining or increasing the depth of navigation channels, anchorages, or berthing areas to ensure the safe passage of boats and ships. Vessels require a certain amount of water in order to float and not touch bottom. This water depth continues to shrink over time as larger and larger ships are deployed. Since massive ships carry the bulk of the goods imported into the country, dredging plays a vital role in the nation’s economy.
The water carrying capacity of Brahmaputra has significantly declined due to silt, which has caused an increase the state’s vulnerability to floods in any season that witnesses good rains. Meanwhile, it has also been under the radar of scrutiny considering the mammoth investment the project will require. This is not for the first instance that a similar project has been initiated. A source said the shifting course of the Brahmaputra is a stumbling block in carrying out dredging. It was decided to take up dredging on an experimental basis in 1966 following which an attempt was made during 1974 to 1976 which was by and large unsuccessful. It was due to high end cost that the exercise remained confined to small stretches. It was again in 2010 that the Dibrugarh administration had taken up the exercise which was again stopped due to heavy expenditure. Thus, it clearly states that uninterrupted flow of fund is a must for the initiation and successful continuation of the project.
Officials of Department of Water Resource, Assam echoed a similar opinion. “The aim of dredging should be developing the banks that have suffered from soil erosion. In several locations the width of the river has increased whereas the depth has decreased. So with the process of dredge mining if the sediments can be restored at the banks it will also help in restoring banks of Majuli and other affected areas,” an official asserted to G Plus.
“The cleanup of the Brahmaputra is crucial and only a perennial exercise of the project can provide a solution to the flood problems of the state. For the project to be a success we will require continuous support from the centre as there is already a fund congestion,” the official added.
Meanwhile it was also reported recently that the World Bank has sanctioned an amount of Rs 980 crores for dredging the Brahmaputra. However, the timely release of fund remains a hurdle. The National Hydrology Project (NHP) funded by the World Bank is also underway for which Assam has been allotted with Rs 47 crores. The project is intended for setting up of a system for timely and reliable water resources data acquisition, storage, collation and management. It will also provide tools/systems for informed decision making through Decision Support Systems (DSS) for water resources assessment, flood management, reservoir operations, drought management, etc. NHP also seeks to build capacity of the state and central sector organisations in water resources management through the use of information systems and adoption of state-of-the-art technologies like remote sensing.
Out of the total outlay of Rs 3,679.76 crores, Rs 3,640 crores has been earmarked for National Hydrology Project while Rs 39.76 crores has been kept aside for NWIC. Out of the total outlay, 50% of the amount, that is, Rs 1,839.88 crores, would be World Bank loan which would be repaid by the central government. The remaining 50% that is Rs 1,839.88 crores would be central assistance from the budgetary support. The entire World Bank’s loan component and central assistance to the states and central organisations shall be passed on to them as grants. It was also informed that most of the sediments are discharged from Arunachal Pradesh rather than China. Thus, the completion of NHP will play a vital role in dredging the river.
Brahmaputra’s average annual flow (water discharge) throughout Assam varies from 8,500 to 17,000 cubic meters per second.
At Pandu Ghat near Saraighat Bridge the average annual floods recorded was 16,000 cubic meters per second.
During floods water discharge reaches its peak and the yearly average peak flow recorded was approximately 51,000 cubic meters per second.
For the Brahmaputra River the highest daily discharge was recorded in August 1962 at Pandu which was 72,726 cubic meters per second.
The lowest daily discharge at the same place was 1,757 cubic meters per second in February 1968.
World Bank has sanctioned an amount of Rs 980 crores for dredging the Brahmaputra