Assessment of Bank-Line Shift of Depota River, Assam using Geospatial tools

Abstract

Bank line migration is an intrinsic process of fluvial landscape as river tries to adjust in order to attain some sort of equilibrium state undergoing vertical and lateral mobility forming floodplain. The Trans Himalayan Rivers are highly susceptible to erosion and bank line migration processes owing to a host of natural and human induced factors. As such a study on Depota river, one of the important north bank tributary of Brahmaputra river have been carried out using remote sensing and geographical information system tools and techniques. A period from 1967 - 2017 have been taken in to consideration to examine the bank line migration pattern resulting from both erosion and depositional processes. The study reveals that the river is severely prone to riverbank shift during the peak monsoon season from May to September. The highest shift of 146.62 m along right bank and 134.11 m along left bank in few reaches were recorded during 1967-2017 wiping huge agricultural fields, tea gardens, human properties, livestocks mainly near Rangapara, Niz-bahbari, Sonajuli, Barjuli T.E., Satai ban gaon etc. Considering nine segments, the total amount of deposition was observed as 99.15 m exceeding the amount of land loss as 48.22 hectares due to the effect of siltation and less cohesiveness among bank materials. Moreover, frequent breaching of embankments has also posed another threat causing massive damages to the floodplain dwellers.