What are the roles of different physical processes in the formation of the meander

A river meander is a bend in a river channel. It usually occurs in the middle and lower course of a river where the land is flat and lateral erosion dominates. The main physical processes that cause the formation of a meander are erosion and deposition. These processes occur at the same time in different parts of the river channel. When a river goes around a bend, it pushes the water to the outer edge, causing an increase in the speed of the water which in turn increases erosion. This part of the river has the fastest flow and this is termed ‘thalweg’. Erosion on the outer bend causes the river to be undercut, forming a steep river cliff. The main types of erosion that occur are hydraulic action and abrasion. The inner bend has shallower water which flows more slowly. Therefore, deposition dominates this part of the channel. Sand and gravel are deposited as a result, creating slip-off slopes/point bars. As erosion continues, the outer bend of a river becomes wider. In addition to this, as lateral erosion dominates the lower course of a river channel, the river valley floor will also be seen to get wider. Over time, the meander will slowly migrate downstream, creating a line of river cliffs at the edge of the valley floor.