Most rivers have an upper (youthful) course, a middle (mature) course and a lower (old age) course. These stages are marked by variations in the characteristics of the river.
The youthful stage of the river is when water flow is the quickest. Waterfalls, potholes, V-shaped valleys and interlocking spurs are features of the youthful stage, and these features are due to erosion. The flow becomes gentler during the mature stage, and the river widens. Curves are characteristic of the middle stage as well. On the inside of the curves, deposition will take place. On the outside, erosion will take place. Land is the flattest during the old age stage. The river has to work hard to make its way to the sea.