Erosion.

Types of erosion:

Hydraulic action- The force of the water forces air into cracks increasing pressure causing parts to break off. The force of the water hitting river bank cause weathering.

Abrasion- Big sediment particles rub against river banks creating a sand paper effect. If this occurs on the riverbed under high pressure then pothholes can be formed.

Attrition- Big rocks that are being carried by the river smash against each other. This results in them becoming smaller and smoother.

Solution/Corrosion- Carbon dioxide dissolves in the river to form a eak acid. This dissolves rock be channel processes.