Assessment of geotechnical properties of the bank sediment to investigate the riverbank's stability along the Ganga river within the stretch of Malda district, West Bengal, India

The shifting of the Ganga has been a long-term phenomenon that has constantly shaped and reshaped the territorial history of Malda district. The present study deals with the analysis of particle size distribution of the bank in Manikchak Diara and assessment of river bank stability by analyzing the particle size distribution of the bank soil, using soil sieving, assessing the river bank stability on the basis of estimated value of Uniformity Coefficient, Coefficient of Gradation and Sorting Coefficient and developing particle size distribution curves and assessment of the bank stability in Manikchak Diara of Malda District, West Bengal. The soil texture along the river bank of Manikchak Diara is attributed by fine to very fine sands which promotes favourable condition of the entrainment of particles from the river bank stratigraphy and induces tensional cracks and finally causes land loss through bank erosion. Most of the soil sample analysis depicted low uniformity co-efficient, sorting co-efficient and gradation co-efficient values which denotes uniform size of the particles available along the river bank of Manikchak Diara. Such uniform size of the particles mean more pore spaces in the soil which also helps easy percolation and easy horizontal sub-surface flow water. The whole situation introduces river bank weakening process in the region. The physical properties of soil in Manikchak Diara plays an important role in reducing soil cohesion and strength properties and invites favourable condition for bank erosion and land loss.