Identifying causes and management of river bank erosion in Majuli Island, India

Abstract

River bank erosion is not only a major concern for those living on the bank, but it also causes huge economic losses to the habitants. Through case studies, it is noted that geogrid application is one of the most accepted and adoptable technique for the protection of slopes and the same is proposed for the protection of river bank of Majuli Island. Finite element-based numerical tool PLAXIS 2D is used for the numerical analysis of proposed river bank protection work to assess its stability as well as deformation pattern. To address the issue of uncertainty in input geotechnical parameters, concept of response surface methodology in combination with numerical analysis and first-order reliability method approach is used for the probabilistic analysis or assessing the performance of the proposed bank protection work in terms of an index, popularly known as reliability index “β”. The proposed methodology saves computational time and effort and useful for preliminary investigations when compared with computationally demanding approach like Monte Carlo Simulations. Through finite element-based numerical tools, it is established that the proposed deign for the protection work using geogrid will help in improving the stability of the slope and facing using shotcrete will help protect the bank for further erosion. Issues of uncertainty in the geotechnical parameters are presented, and it is emphasized that probabilistic approach is vital in assessing the stability in probabilistic framework as it treats uncertainty in mathematical framework and bring rationality in decision making.