What are 3 main types of work a river carries out along its valley?

The three main types of work a river carries out along its valley are:

Erosion: Rivers erode their beds and banks through the processes of abrasion, attrition, and hydraulic action. Abrasion occurs when rocks and sediments carried by the river scrape and grind against the river bed and banks. Attrition occurs when rocks and sediments collide with each other and break into smaller pieces. Hydraulic action occurs when the force of the water itself dislodges and carries away sediment.

Transportation: Rivers transport eroded sediment downstream. The size and shape of the sediment particles that a river can transport depends on the velocity of the water. Larger and heavier particles are transported during periods of high flow, while smaller and lighter particles are transported during periods of low flow.

Deposition: Rivers deposit sediment when the velocity of the water decreases. This can occur when the river enters a wider or flatter area, or when it meets an obstacle such as a dam. The sediment that is deposited forms landforms such as floodplains, deltas, and alluvial fans.