What is Alluvial Fan in geography?

The deposit of sediment formed by a swift-flowing stream when it enters a plain or an open valley, these are common in dry regions. The alluvial fan grows many kilometres (miles) across, and several fans made by neighbouring streams often unite to from a continuous plain, known as a piedmonl alluvial plain; the depth of alluvial material may vary and sometimes it may be hundreds of metres. Much of the water is absorbed by the loose material of its fan. The soil formed by Alluvial fan is of great agricultural value.