What are the stages of a river?

the three stages of a river are- the upper course or the mountain stage- in this stage the river undergoes the mountains that are really very steep so the river has freat cutting power in this stage. the main work of the river in this stage is erosion and transportation. the middle course or the plain stage- the ground becomes less flat and the river slows down. the river becomes very smooth , but still it erodes some of the rocks. in the end of the middle stage , deposition takes place. the lower course or the delta stage- in this stage, the river slows down completely and forms a delta.