Changing Dynamics of Rani-Chapori River Island of Brahmaputra River, Assam

Abstract

The fluvial processes carried on by the river Brahmaputra have resulted in the creation of a number of river islands and sand bars which are of much ecological significance. Rani Chapori is such an island created and affected by the river. The study indicated the importance of bankline migration and sediment composition of the river island upon the morphology and stability of the island. Using the sieving instrument and pipetting method, the sand texture was analysed and using remote sensing data and related software, the bankline shift was found out. The results revealed that the morphology of the river island has continuously undergone changes as a result of the fluvial actions of the river and the sediment characteristics too played a role in it. The size of the river island in 2016 increased by about 9.86% in comparison to 2005 and decreased by 8.24% in comparison to 1961, while the perimeter has decreased by 0.13% in 2016 as compared to 2005 and about 10.98% with respect to 1961. The total bankline shift of the north bank in the adjoining areas of the island in the period 1961-2016 was 2.8095 km towards the right as a result of erosion while the left side shift was 0.453 km due to deposition. The right-side shift of the south bank due to deposition was 0.67 km while the left side shift was 0.41 km due to erosion. The unstable morphology of a river island affects the life that thrives on the land and thereby, the ecosystem which makes it utmost necessary for the policymakers and conservationists to shift their immediate focus to help preserve such river islands.

Keywords: Bankline erosion, Bankline shift, Morphology, River Island, Sediment.