Brahmaputra shifting southward?

Guwahati, May 02: The Brahmaputra would have caused immense peril to major human habitats of Asom if there were no man-made flood control measures.

Geomorphological evidences have suggested that the river is gradually shifting more than two kms towards south from its present course.

An expert in the State Water Resources department told UNI that the southward drift of the Brahmaputra is aggressive at places like Polashbari in Kamrup district, Hatimura in Morigaon and Nimati Hatisal, Kokilamukh and Kolbari in Jorhat district.

However, the rate of the drift has of late been retarded by the spurs and bullheads erected at the vulnerable areas.

'' This is not an instant process. It has been going on since years. We have found through studies that the Brahmaputra has shifted more than 10 km from 1915 to 1998,'' an expert said.

Referring to an official study conducted by a senior research officer from Pune, the expert said it is because of the flood control measures like spurs, bullheads, porcupines and revetments taken all along the course of the river, that the shift has been temporarily retarded to a great extent.

Slow deformation of the Indian subcontinent due to horizontal movement of the tectonic plates and the subsequent rise of the Himalayas are contributing factors to the southward shifting of the Brahmaputra.

According to geomorphologists, the Indian plate is moving towards the northeast at 18 mm every year, while the Himalayas are rising at about five mm each year.

However, some rocky mountains like the Burapahar (near Kaziranga), Karbi hills, Meghalaya hills and Garo hills are preventing the river's drift.

The expert claimed that places like Nimatighat in Jorhat, the shift has been aggressive. ''It was up to 3 km between 1986 and 2001,'' he addded. The spurs erected at places along the river, like Dibrugarh Town Protection Spurs, Nimati Hatisal spurs, Rangapara spurs (both in Jorhat) and Dhubri Town Protection Spurs have checked the drift of the river.

The expert further assured that there would be no fear of devastation because of the flood control measures adopted.

Besides deflectors, and other short-term erosion control measures have also retarded the slide.

''The life of the spurs are not more than 50 years,'' he cautioned. He further stressed the need to initiate long-term erosion control measures.

Specifically pointing to Morigaon and Nagaon districts, which are stated to be the most vulnerable areas as of now, the expert said the future of Nagaon town lies on the Hatimura embankment.

''If the dyke is breached, the Brahmaputra may flow southward through Kalang and submerge major portions of Nagaon, Sonapur and even Dispur,'' he warned.

Ruing at the failure of the proposed Dihang-Dibang multipurpose project in Arunachal Pradesh, the expert said, ''had it been constructed, it would have tamed the Brahmaputra to a great extent.'' Alluding to another study, he said another geophysicist had said ''in the last 100 years, the Brahmaputra has shifted nearly 22 km towards south in middle Asom.'' As a result of the shifting hundreds of bills were formed on the north bank, like Majuli bill, Miri bill and Salmari bill,'' he observed.

UNI