NEW DELHI, May 20? The very existence of Majuli ? the largest river island ? situated within the two arms of the mighty Brahmaputra, is under threat with acute erosion engulfing chunks of it, scientists have said. If no corrective measures through proper scientific planning and management are taken, Majuli, will soon be engulfed by Brahmaputra and become extinct from the world map, scientists from the Regional Research Laboratory and Dibrugarh University, said.
?When the river floods the state every year, the entire population of Majuli Island fears that it may be engulfed by the mighty Brahmaputra,? they said in a report in Current Science journal. Stating that their study indicated that a considerable portion of Majuli Island was being eroded by floods every year, the team said the land area of the island, a seat of the Vaisnavite Movement, as evidenced from the Indian Remote Sensing Satellite imageries of 1998, was 577.65 square kilometre compared to 1,245 square kilometre as indicated in historical records.
A comparison of the data of 1975 topographic base map with the Indian Remote Sensing Satellite imageries of 1998 showed that the area had decreased by 35.97 square kilometres, they said adding the Brahmaputra channel has increased its width from seven to 9.25 km from 1920 to 1998 with significant expansion on the southern side of the island.
The data indicates an erosion rate of 1.9 square kilometres per year for the period 1920-98, they said. The report said that the island faces an acute erosion problem as no permanent anti-erosion measures based on proper geohydrological models have been adopted so far. Geomorphologically, the island, Majuli, forms part of the flood plains of the Brahmaputra river. It has a population of 134,395 and an area of 900 square kilometres. The island has 155 villages.
Majuli suffers from severe bank erosion on its southern side due to the erosive action of Brahmaputra, and on its northern side due to the Subansiri river. The river island is subjected to severe annual floods under the influence of the South West monsoon. Several studies have indicated that the Brahmaputra river changed its course abnormally after the Great Assam Earthquake of 1950 with a magnitude of 8.6 and the attendant historic flood.
There was a balance between sediment supply and transport up to 1950 which was disrupted by the earthquake which produced severe landslides within hilly tracts and provided a large quantum of additional sediment. Descending into the plains, the extra sediment choked the river channel gradually and initiated bank erosion causing channel-widening, the report said adding many other towns, besides Majuli, on the banks of Brahmaputra are also under threat due to abnormal changes in the river course.