| Abstrakt: |
The rivers of Indo-Ganga–Brahmaputra (IGB) plain are widely known for their dynamicity and hazard proneness. All of the large rivers that originated from Himalaya and flowing into the IGB plain (like Ganga, Ghagra, Ramganga, Rapti, Bagmati, Koshi, Teesta, Brahmaputra, etc.), shift their position vigorously and create massive kind of bank erosion. In the present study, we have selected 35.30 km alluvial reach of lower Ramganga river which is one of the major tributaries of the Ganga River. The study aims to quantify the amount and rate of bank erosion and accretion phenomena, also to find out the nature of bank erosion and accretion. In the present paper, we assessed the bank erosion and accretion of 91 years. We have taken 1923 toposheets, and Landsat images of 1972, 1981, 1993, 2003, and 2014 for the study. Demarcation of bank lines and estimation of bank erosion and accretion areas (for left and right bank separately) were done by using ArcGIS. Detailed field works were also done for investigating the nature of bank erosion and accretion as well as for bank line demarcation. The study reveals that in all of the evaluated periods, the river has experienced differential rates and amounts of bank erosion and accretion. The widening of channel, extension of meander bends along with lateral movements of the channel and chute cutoff are mainly responsible for bank erosion and accretion, while liquefaction and flowage of bank materials and shear failure were the principle mechanisms for that. |
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