Morphological dynamics of the rivers of Brahmaputra

This study documents the sequential morphological dynamics of rivers of Brahmaputra. Landsat images for the year of 1976 and 1987-2016 (thirty consecutive years) are used in GIS environment to document the activities that have been shaping and reshaping the morphology of the rivers. The use of thirty year consecutive images facilitates an explicit assessment of morphological changes. Apparently, distributary activities, meandering activities, breaches and avulsions, and confluence migrations are the dominant geomorphic agents of morphological changes. A range of distributaries activities are readily noticed in Brahmaputra plain. The plain is densely dissected with numerous rivers and rivulets, and distributaries activities often lead to reorganization in channel network. Considering the frequency of incidence and preserved imprints of abandoned channels, majority of the rivers of Brahmaputra can be categorized as free meanders. Difference in fluvio-geomophic setups of rivers of both the banks is reflected palpably in meandering activities. The upper stretch of Brahmaputra encompassing the rivers Simen, Gai and Jiadhal is found to be the most active in terms of avulsions. High seasonal flow, large sedimentation and absence of distinct river bed in some stretches are presumably leading to these frequent avulsions. The river Simen, further, exhibited repeated confluence migration through avulsion near its confluence with Brahmaputra. The explicit picture of the morphological dynamics of rivers of Brahmaputra at basin scale presented in this work is a key aid in formulating riverine management programs which is conceivably among the most water-troubled region of the country.