Brahmaputra River Bank Failures—Causes and Impact on River Dynamics

Abstract

The Brahmaputra River has been the lifeline of north- eastern India since ages. This mighty trans-Himalayan trans-boundary river runs for 2880 kms through China, India and Bangladesh. The gradient of the Brahmaputra River varies from very steep near the source at the Tibetan plateau (1:385) to very flat in the lower part of Bangladesh (from 1:11,340 to 1:37,700). Geomorphologically, the Brahmaputra basin is very unstable as it is located in a high seismic zone. The Brahmaputra is a large alluvial river with highly variable channel morphology and a high degree of braidedness. The dominant flow is multichannel flow acknowledged to be very complex for mathematical modelling. The problems of flood, erosion and drainage congestion in the Brahmaputra basin are gigantic. The river bank failures are responsible for large scale bank erosion, aggradations and widening of the river channel. This in turn is responsible for lateral channel changes of the Brahmaputra River in many reaches leading to a considerable loss of good fertile land each year. Bank dynamics is also causing shifting of outfalls of its tributaries bringing newer areas under waters. Frequent changes of channel courses and bank erosion with high rate of siltation have also been identified as major threats to the riverine biota. This in turn has a negative impact on the sustainability of the wetlands. Degradation and destruction of the wetlands have considerable impact on the deteriorating flood hazard scenario in the state. This paper outlines the types of river bank failure mechanism and erosion process in the Brahmaputra River. The paper also presents information on the river reaches of Brahmaputra suffering from high bank erosion rates and the impacts of bank erosion on the Brahmaputra basin and people of the region.