The sides are known as the river bank or river banks.
riverbanks
The sides are known as the river bank or river banks.
the river running through rock wear it down into deep valley with the steep sides what is it called
A Flood.
A v-shaped valley eroded by a river is called a river valley. This type of valley is characterized by steep sides and a narrow bottom, formed by the erosive action of the river over time.
Floodplain
Such structure could be called a Canyon.
river bank.
Floodplain
Floodplain
Floodplain
banks