Describe and explain the formation of a meander

Meanders are bends in a river. The formation first develops from alternating bars of sediment, called riffles. Low flows of water in the river have a low hydraulic radius which means there is not enough kinetic energy for sediment to be transported. Thus, where sediment in deposited, areas of high frictional contact are created, and the water must find a way around them. Fast flows around the riffles create pools because the water erodes the river bed and transports the material. Pools and riffles cause the water to move side to side and create the first signs of bending in the river channel.

At times of higher flow, the water swings round riffles because of centripetal force and undercuts the opposite bank. The process of erosion occurs where there is fast flowing water and less frictional drag. Hydraulic action and corrosion cause the bank to be undercut and collapse on the outside. While, on the other side of the channel, a lower hydraulic radius causes the water to deposit sediment and create a slip off slope. The combination of these processes causes the river to move across the flood plain and create a meander. Over time, helicoidal flow constructs several meanders to develop next to each other in an ’S’ shape because the sediment eroded on the outside of one bend, is deposited on the inside of the next.