A river makes a long journey frim the mountains to the sea.
The source is where a river begins.
The mouth is where the river ends at the sea.
The course is the journey from the source to the mouth.
The course of a river has three parts:
- The upper course is near the source. The river is narrow and flows through the mountains. It has little water and flows very fast.
- The middle course flows through plains. The flood plain is the flat area on each side of the river. It has more water and flows more slowly.
- The lower course is near the mouth of the river. The river is wide and the water flows slowly.
I recommend you to watch this video in youtube: The River Severn From Source to Mouth.