Fluvial Landforms - from Fluvial Deposition Flashcards
Explain the characteristics and formation of Braiding.
Braiding occurs when rivers are carrying a vast amount of eroded sediment (e.g. in meltwater).
If the river’s velocity drops, or the sediment load becomes too much for the river to carry, sediment is deposited in the channel.
This causes the river to divide into many small, winding channels that eventually rejoin to form a single channel.
Explain the characteristics and formation of Flood Plains.
When a river overflows its banks and floods the flat land either side of the river (the flood plain), there’s an increase in the wetted perimeter and reduction in hydraulic radius.
This increases friction, reducing the velocity of the river and causing fine silt and sand to be deposited across the flood plain.
Explain the characteristics and formation of 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.
Explain the characteristics and formation of Deltas.
When a river reaches the sea (or a lake), the energy of the river is absorbed by the slower moving water of the sea (or lake).
This causes the river to deposit its load. These deposits build up on the sea bed, until the alluvium (deposited sediment) rises above sea level, partially blocking the mouth of the river.
The river has to braid into several distributaries in order to reach the sea, forming a delta.
