Describe and explain the formation of an oxbow lake. (6 marks)

Oxbow lakes are most commonly found in the middle course of the river, where the river has more energy and higher discharge. A meander is first formed as a result of deposition and erosion - velocity is higher on the outside bend which means erosion occurs, forming a cliff face. Deposition occurs on the inner bend as a result of slower velocity, forming a slip off slope. The meander is gradually made more pronounced as a result of the deposition and erosion changing the depth, and subsequently the levels of friction, which again determines the velocity and erosive power. The neck of the meander will gradually narrow. In the event of a flood, when the river has high discharge and energy, it will take the fastest course, which cuts of the meander. Deposition will occur in the channels, and an oxbow lake will be formed. Evaporation will occur and the area is likely to become vegetated, leaving a scar of the oxbow lake. 

N.B: diagrams are often appropriate to illustrate the formation.