Sediment properties and processes influencing key geoenvironmental aspects of a large alluvial river, the Brahmaputra in Assam
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The research attempted to evaluate key sediment properties and processes of a large alluvial river, the Brahmaputra in Assam, India and examine how different sediment properties and processes influence major geoenvironmental behavior of the river. Based on primary as well as secondary data, the thesis focusses physico-chemical properties of sediments including contamination status, sediment budget, bank line shifting, river bank erosion, role of geochemical properties of bank materials in erosion, braiding and land use & land cover of the river in post-monsoon months. One objective of the research was to understand geoenvironmental changes of Brahmaputra and seeking solution to the bank erosion problem. Suspended sediment and bed sediment samples were collected from six different locations of Brahmaputra River in Assam. Considering severity of erosion problem in the last few years, another six locations were selected for collection of bank material samples. pH, organic content, carbonate content, sodium absorption ratio, exchangeable sodium percentage, cation exchange capacity, mineralogy and particle size of collected sediments and bank materials were analyzed by standard methods and instruments. Angle of internal friction and cohesion of bank materials were estimated by direct shear tests. Role of bank material properties in erosion were studied with binary logistic regression using SPSS. Braiding, erosion-deposition and land use and land cover of Brahmaputra was studied extracting information from Landsat images using Remote sensing and GIS techniques.
Supervisor: Chandan Mahanta