English to Russian Science Geography ландшафты

Floodplain - Each time a river overflows its banks, it deposits sediment, which accumulates to form the river’s floodplain.

Alluvial fan - At the point where a river emerges from a mountain valley onto flatter terrain, the sediment it releases radiates out to form an alluvial fan, one kind of alluvial plain.

Valley plain - As a river meanders through a wide valley, it erodes the bank on one side and deposits silt on the other, gradually forming a flat plain across the valley.

Как я понимаю, это типы равнин и просто "равнина" не подходит. Спасибо за помощь.