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Braiding process and bank erosion in the Brahmaputra River
M.P. Akhtar, , C.S.P. Ojha
Published in
Volume: 26
Issue: 4
Pages: 431 - 444
The present work explores relations between stream power, braiding intensities and bank erosion in certain stretches of the Brahmaputra River. In this paper, an objective approach is presented to enable quantitative assessment of spatio-temporal behaviour of channel braiding process of the Brahmaputra River by using the Plan Form Index and corresponding estimation of stream power to establish a behavioural pattern of variability of potential energy expenditure. The braiding index is compared for discrete years to understand the morphological behaviour. Subsequently, a real time estimation of stream power for certain stretches of Brahmaputra River is done in order to analyse its variability in braiding intensity and bank erosion. The paper presents the dynamic behaviour of the channel pattern of the Brahmaputra River System in Assam valley of India over a time span of 18 years. The procedure addresses the selection of input parameters from digital satellite images, comprising scenes for the years 1990, 1997 and 2007 with specific dates, from Dhubri near Indo-Bangladesh Border to Upper Assam. Deployment of GIS technique has been made to extract the required parameters to derive Plan Form Indices for the entire study reach. Stream power estimation is done for corresponding latest floods and for corresponding dates of image scenes. The study indicated that due to consistent aggradation of riverbed inducing temporal declination of stream power, there is an occurrence of wide spread braiding. This in turn incurs substantial yearly land loss due to bank erosion, caused by flow concentrations due to temporal evolution of multiple channels in the Brahmaputra River. © 2011 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.
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