Landforms in the lower course of a river
The volume of water in a river is at its greatest in the lower course. This is due to the contribution of water from tributaries. The river channel is deep and wide and the land around the river is flat. Energy in the river is at its lowest and deposition occurs.
Rivers flood on a regular basis. The area over which they flood is known as the floodplain, and this often coincides with regions where meanders form. Meanders support the formation of floodplains through lateral (sideways) erosion.
When rivers flood the velocity of water slows. As a result of this, the river’s capacity to transport material is reduced and deposition occurs. This deposition leaves a layer of sediment across the whole floodplain. After a series of floods layers of sediment form along the flood plain.
When a river floods more substantial material and the majority of deposition occurs next to the river channel as the result of increased friction (with the flood plain). The velocity of the river slows and therefore rapidly reduce its ability to transport material. This leaves a ridge of higher material next to the river channel on both banks of the river known as a levee.
An estuary is a wide, sheltered body of water found at a river’s mouth where it broadens into the sea. It is a combination of salt water from the sea and fresh water from a river. As the river meets the sea at high tide, it slows the flow of water leading to deposition. Mudflats and saltmarsh form in these areas. The mudflats can be seen at low tide but are covered by water at high tide. Over time, the mud flats can become colonised with vegetation forming salt marshes.
Deltas are often found at the mouth of large rivers. An example is the Nile Delta. Deltas are formed when a river deposits material faster than the sea can erode it.
The Nile Delta – source
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