Answer: The alluvial soil is formed by the rivers that erode the rocks.
Step-by-step explanation:
The rivers flows through the mountains and erodes the rocks. The sediments like silt and gravel get accumulated at the banks of the river that were flooded by the rivers.
The deposition of the eroded sediments results in the development and formation of the alluvial soil. The accumulation of the alluvial soil leads to development of alluvial land.