Bank Erosion and Channel Abandonment of the Sankosh River in India

Bank erosion is an important process of channel abandonment of the Sankosh River. In alluvial river bank erosion is frequently occurred which caused by several factors i.e. high discharge, flow diversion, migration of bar, cohesiveness of the bank material and different anthropogenic activities viz. construction of embankments, excessive gravel and sand extraction from the river bed. At the same time, sufficient energy is also considered as an important factor for bank erosion. It is mentioned that bank erosion for channel migration demand available stream energy which occurred during bankful stage. Moreover, the combined effect of both the physical and anthropogenic processes causing bank erosion and formation of abandoned channel along the Sankosh River in India. Generally, the River erodes one bank as well as deposition occurred on the other bank and sometimes bank erosion may also be occurred in the both bank of the river channel. It is noticed that bank erosion is high during peak discharge period due to high current of water flow and excessive load of the river. In this way wetting of the bank materials lower the shear strength of the bank and the bank strength reduce remarkably and as a result create fissures and cracks over the surfaces. Moreover this condition generates tension within the bank soil which leads to slip failure. As a result the widening of valley occurs by this bank erosion process and the meandering of the river increases day by day and initiates the process of channel abandonment.