Changes in Morphometric Meander Parameters and Prediction of Meander Channel Migration for the Alluvial Part of the Barak River

A common phenomenon associated with the alluvial river is its meandering action which leads to lateral migration and thus geomorphic hazards. Predicting and preventing this migration is both difficult and necessary. Barak river is one of the highly meandering rivers flowing through the alluvial plains of Assam, India. It is observed that there is a regular shifting of the river banks and development of cutoffs which create uncertainty to the people residing nearby. Therefore, in this study planform geometry and migration behaviour of the Barak river is examined considering 12 representative meandering reaches using multiperiod Landsat remote sensing images, field investigations of channel bed and bank properties and riparian vegetation cover. An attempt is made to describe and evaluate the empirical approach and time sequence extrapolation method to predict channel migration. Channel wavelength to channel width ratio ranges between 5.53 to 12.9, and the bend curvature ranges between 1.1 to 3.93. Rate of river migration varies between 0.54to 85.69 m/year. Sinuosity in most of the meandering reaches is greater than 1.5. Results show that lack of significant riparian vegetative cover, high precipitation and presence of fine sands with very low clay content are probably the main elements responsible for the planform changes. The results of the prediction of meander migration obtained from selected empirical methods show that only Nanson and Hickin method shows a moderate correlation with R-2=0.50. Time sequence extrapolation method was used to predict the radius of the best-fit circle for the year 2025 and 2030. Results of the time sequence extrapolation method indicate that the maximum and minimum radius of the best circle fit for the year 2025 is 1254m at reach-8 and 462m at reach-7 respectively, and maximum and minimum radius of the best circle fit for the year 2030 is 1319m at reach-8 and 387m at reach-12 respectively. It is believed that the outcomes of this study could form a base in river training works and in understanding and predicting the future dynamics and bank migration of this alluvial river and other river of similar geomorphic setting.