River formation is the process by which a river is created and shaped over time. It involves the erosion of land, the deposition of sediment, and the movement of water. The most common type of river formation is DELTA formation, which occurs when a river meets an ocean or lake and deposits sediment at its mouth. This sediment builds up over time, creating a fan-shaped landform known as a DELTA. Deltas are important for providing habitats for wildlife, as well as providing protection from flooding and erosion.