Give a geographical reason for each of the following:

(i) Erosion is the dominant activity of a river in its upper course.

(ii) Landforms of deposition are more prominent in the middle course of a river.

(iii) All the rivers do not form deltas.

(i) Erosion is the dominant activity of a river in its upper course because at this stage, the river flows swiftly, for the gradients are steep. Under the impact of rush of water and the load the river carries, erosion action is swift and effective.

(ii) Landforms of deposition are more prominent in the middle course of a river because at this stage, the gradient is reduced and the river flows more slowly. The energy required to transport the materials is just enough to drag large particles and the lateral cutting is more active than down cutting.

(iii) All the rivers do not form deltas because there are certain conditions for the formation of deltas, which include nearly calm sheltered sea, large amount of sediment supply and a reasonable size of the river.