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1 2021

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Meander migration and cut-off dynamics of Lower Disang River (Assam, India)

Begum Kashmiri, Sarkar Subhajit, De Sunil Kumar

Studia Geomorphologica Carpatho-Balcanica

2021

Vol. 55

45--69

Meander migration and cut-offs are important mechanisms causing changes in river channel morphology. The present work aims at investigating the dynamics of meander migration and cut-offs of the Lower Disang River (Assam, India) and its relation with planform parameters. Channel migration and cut-offs between 1916 and 2017 were studied on an approximately 203.89 km long meandering alluvial reach of the Lower Disang River. Topographical sheets, satellite imageries and Google Earth images (1916, 1969, 1990, 2005 and 2017) have been used to map, quantify, and analyse the development pattern of the meander bends. Only five natural cut-offs occurred during the 101-year time span in the study area. However, numerous cut-offs have occurred in the pre-1916 period, which is seen in the form of traces of oxbow lakes on its floodplain. No cut-off has been formed in the post-2005 period. For the period between 1916 and 2017, the average rate of lateral channel migration has been 1.35 m .y –1 due to the combined process of progressive migration and cut-off. An average of 2.98 % of the total channel length changed via cut-off while 97.02 % of the channel length changed by gradual migration. As a result, of low cut-off frequency and progressive increase in channel length through migration, there is a steady build-up of sinuosity and increasing complexity in meander forms. Thus, cut-off has been less dominant mode of channel change than progressive migration.