Meanders
Meanders are formed by a combination of the processes of erosion, transportation and deposition along a river. Meanders are curves or bends along a river which are usually found in the middle or lower course of a river, or where the floor of a valley is broad and the gradient is gentle.
At a meander, erosion occurs on the outer bank of a river, and the eroded sediments are transported to the inner bank where they are deposited. Here, the water in the channel moves in a spiral fashion. The speed of the river also differs along its outer and inner banks.
Along the outer bank, the speed of the river is high because there is less friction at the outer bank. Thus, the river has more energy and erosion can occur. Over time, the outer bank of the river gets undercut and a steep-sided bank, known as a river cliff, is formed.
The sediments removed from the outer bank are carried by the flow of the water and deposited along the inner bank. Deposition occurs at the inner bank because the friction between the inner bank and the water is greater than at the outer bank. This reduces the speed and causes the river to drop its load. Over time, as more sediments are deposited, the water becomes shallower at the inner bank and the river channel becomes asymmetrical. A gentle slope formed by the deposition of sediments along the inner bank, known as a slip-off slope, is formed. This process is repeated as the river moves downstream.
Example:
Examine closely and you can see how this meandering river has changed its course over the years. It's the River South Esk in Angus, Scotland.
Source: Earth: Our Home 3 (Full Geography
