Estimating bank-line migration of the Brahmaputra River in the Middle Brahmaputra floodplains of Assam, India using Digital Shoreline Analysis System

The Brahmaputra River, in its middle reaches, has eroded many pockets of land, eventually leading to drastic bank-line shifting. This study aims to analyze the bank-line migration of the Brahmaputra in the Middle Brahmaputra floodplains of Assam, India, over a period of 30 years (1990–2020) and forecast their positioning using Digital Shoreline Analysis System (DSAS). End point rate (EPR) was used to estimate bank-line migration over three decades (1990–2000, 2000–2010, and 2010–2020). Both end point rate (EPR) and linear regression rate (LRR) were used for calculating long-term migration from 1990 to 2020. EPR calculated bank-line migration between 2 years and LRR utilized all given bank-lines to calculate average bank-line shift in a year. The model also forecasted bank-line migration for 2030 and 2040 (10 and 20 years) using Kalman filter. The findings revealed that bank-line migration was more prominent along the river’s south bank and the river channel was observed to be migrating in a southward direction. The average shift of the right bank was around − 8.15, 11.83, and − 4.5 m/year during 1990–2000, 2000–2010, and 2010–2020, respectively. The left bank showed an erosive trend with an average positional shift of − 57.02, − 53.65, and − 38.66 m/year during 1990–2000, 2000–2010, and 2010–2020, respectively. The ‘−’ values represent erosion and the ‘+’ values indicate accretion. The forecasting of the bank-lines showed that the river would likely continue to erode its banks leading to channel widening. The study demonstrated the severity of bank-line migration and erosion in the study area.