banks
river bank.
A V-shaped valley
The sides are known as the river bank or river banks.
the bottom of a river
A river channel
The "Main Channel".
The River Channel is just before the the river meets the mouth or sea.
The River Severn is the main river that flows into the Bristol Channel.
The river bed
the river Oise and the river Marne are important tributaries to the Seine river.
channel
If a river channel has a steep gradient, the river flows faster and has more erosive energy.