GEOMORPHOLOGY 

A drainage system refers to the network of rivers, streams, and other water channels that collect and transport surface water (rainfall, snowmelt) across a landscape, eventually draining into a larger body of water such as a lake, sea, or ocean. 

1. Types of Rivers

Rivers are classified based on their water flow:

• Permanent rivers – Flow year-round (e.g., Nile, Amazon).

• Periodic rivers – Flow seasonally (e.g., Limpopo in dry seasons).

• Episodic rivers – Flow only after heavy rainfall (e.g., desert rivers).