
As rivers slow in speed, their ability to carry sediment decreases. Sediment tends to be deposited where the flow of water is the slowest. This is usually at the widest part of the river, where it meets a larger body of water. The pile of sediment at the mouth of a river or stream is called a delta. Deltas can be found where streams flow into lakes or oceans. As new sediment is deposited in the delta, the stream will regularly change its course. Eventually it makes a fan-shaped area of sediment, shaped like the Greek letter delta (Δ). The delta is where river water begins to mix with a body of water, such as a sea or lake.