The narrow strip of land on both sides of the rivers is called cover flood plains
The flood plain. Delta
a canyon, gorge or vale
In its flood plain
No, the area drained by a river is a river basin or drainage basin. The flood plain is in the lower valley reaches, where heavy rain can cause the river to flood, often bursting over flood defences, and for the water to flood over a large area.
It is the flood plain.
A 'flood plain' usually.
flood plain
the flood plain
River bank, flood plain, water meadow.
The flood plain
Flood plain
the flood plain