Levees
Levees are natural, raised embankments formed as a river overflows its banks.
- During a flood, material is deposited across the whole flood plain as the river loses velocity and energy due to increased friction
- The heaviest material e.g. sand and gravel is dropped first, closest to the river channel
- Over time this material builds up on the river bank, creating a levee.
Deltas
A delta occurs where the river has to braid into several distributaries in order to reach the sea
- When a river reaches the sea or a lake, th energy of the river is absorbed by the slower moving water of the sea or lake
- This causes the river to deposit its load - deposits build up on the sea bed until the alluvium (deposited sediment) rises above sea level, partially blocking the river mouth.
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