Article ID Journal Published Year Pages File Type
4685101 Geomorphology 2012 12 Pages PDF
Abstract

The Brahmaputra is one of the largest tropical rivers of the world and is located in an area of high structural instability as evidenced from the presence of a large number of earthquakes in the Himalayan catchment through which it flows. Syntectonic evidence of changes in the morphodynamics is difficult to identify for the large rivers. Nevertheless, we note that the Brahmaputra River has become astonishingly large in planform in a historical timescale. Reconstruction of planform changes over a period of 90 years in the upper reaches of the Assam valley shows that the 240-km-long channel belt is widening all along its course in the region. From the average width of 9.74 km in 1915, the channel belt has widened to the average width of 14.03 km in 2005 (44% widening), and in certain reaches the average widening is as high as 250%. However, the bank line shift is not symmetric along both banks. Further, the planform characteristics of the Brahmaputra River reveal significant spatial and temporal variability from upstream to downstream reaches, and we attribute this variability to tectonogeomorphic zonation of the river based on subsurface configuration and channel slope. Further, the tributaries joining the northern and southern banks of the Brahmaputra differ remarkably in terms of river dynamics, and this is attributed to the differences in tectonic regimes of the Himalaya in the north and the Naga Patkai hills in the south.

► A 240 km stretch of the Brahmaputra channel belt widened by 44% within 1915–2005. ► Significant difference in the nature and extent of planform bank line shift ► Spatial variability in morphodynamics is attributed to tectono-geomorphic zonation. ► Northern and southern bank tributaries show big differences in morphodynamics. ► A more dominant control of Himalayan tectonics compared to the Indo-Burmese Arc

Related Topics
Physical Sciences and Engineering Earth and Planetary Sciences Earth-Surface Processes
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