The flow of river can be divided in three sections. Each section is called a ‘Course’. There are three courses of river.

They are:

1. Upper Course
2. Middle Course
3. Lower Course.

(1) Upper Course:

1. When a river starts from mountainous region, it flows quickly with lots of energy. This causes intense erosion.
2. The upper course carries huge volume of sand and sediments along with it.

(2) Middle Course:

In the middle course, the river flow slowly, but spreads on wide areas. This course transports lots of sediment and hence the river looks muddy.
(a) Formation of meanders: The fall of river found in upper course changes to sideways motion. The river starts moving, to the right side then the left side, causing bends or loops in the shape of horseshoe (i.e., animal hoof) in the river. These bends are called meanders.
(b) Formation of lakes: At times due to the meanders and the impact of floods, the loop formed during meanders gets cut-off from the main channel. The cut-off loop is called an ox bow lake.

(3) Lower Course:

1. The end of the river is called the mouth. Lower course refers to the end of the journey of the river.
2. In the lower course, the river has a high volume of water and a large discharge of sediments but at low energy level.
3. The river channel is now deep and wide and the landscape around it is flat.

(a) Formation of delta: At the mouth of a river, there is often a river delta a river delta is a large, muddy area where the river splits into many different slow-flowing channels i.e., tributaries. Delta is a highly fertile triangular-shaped plain.