Erosion-induced riverbank failure causes huge loss of lives and economy every year in India. However, studies pertaining to riverbank erosion mostly emphasize the sedimentation caused by the erosion and its aftereffects. In this study, a model is developed to predict the instability in the Barak riverbank caused due to erosion, quantified using mathematical models, and to assess the improvement in the stability of the riverbank after incorporating the gabion mattress as a remedial measure for erosion. The prediction of riverbank failure is based on the numerical model. A model of the riverbank is developed using the GEOSTUDIO software package for prediction analysis. The cross-section of the riverbank is updated as per estimated erosion, and the earthen structure’s stability is checked by varying parameters. It is observed that the stability of the riverbank improves significantly after the incorporation of a gabion mattress as a remedial measure.