Geotechnical Investigation and stability analysis of River Bank retreat along the Critical Reaches of Brahmani River, Odisha, India

River embankment breaches across the critical reaches of the Brahmani River, causing vulnerability of livelihood, agricultural land, and loss of livestock. Planform and slope-forming parameters are implemented to decipher the critical zones of avulsion along the Brahmani River. River bank retreats along very high to high moderate zones of insitu migration have been monitored along the middle and lower reaches of Brahmani River, Odisha. The uncertainties in predicting bank failure mechanisms result from a lack of detailed observations of a bank collapse. The soil samples are collected for laboratory investigation to decipher the geotechnical properties of soil samples. Sieve analysis, proctor compaction test, atterberg limits and soil triaxial test are performed to determine grain size, moisture content, density, cohesion and angle of internal friction. The saturated/Unsaturated flow of river bank slopes using finite element method has been simulated using fully coupled flow deformation analysis in Plaxis 2D. The river bank stability analysis has been monitored with river water level fluctuation data from 2000-2013 for a better understanding of factors influencing bank changes and various processes of seasonal scale. Seven major flood events occurred from 2000 to 2013, with the highest discharge of 12000 cumecs recorded during peak flood events. Bank simulations are performed by linking river water level, precipitation, discharge and groundwater flow of flood events. The simulation of river bank failure allows identification of (i) probable zones of failure of the slopes, (ii) effects of slow and rapid draw down on stability mechanism, and (iii) role of discharge, precipitation and river water level fluctuation in factor of safety. The result of river bank simulations represents the bank erosion process and its relative dominance according to the seasonal hydrological cycle and bank geometry.