There are four types of erosion: Attrition, Abrasion, Solution and Hydraulic action.
Hydraulic action- the force of water that wears away the river bank from underneath.
Attrition- rocks being carried by the river smash together and break into smaller pieces. Over time, they become smaller and are reduced into fine particles called slit.
Abrasion- stones that are carried by the river bump into the river bank and wear them away.
Solution- acids in the water slowly dissolve the river banks and the stones- especially limestone- that the river is carrying.