Depositional landforms
Floodplains
A An area of low-lying land next to a river which is prone to flooding. is a landform of the lower course. It is a flat area of land which is covered in water when a river bursts its banks. They form due to both The wearing away of pieces of rock, soil or other solid materials. and When rocks carried by the sea water wear away the landscape, eg cliff face/headland.. Erosion creates a wide, flat area on either side of the river. During a flood, material being carried by the river is deposited (as the river loses its speed and energy to transport material). Over time, the height of the floodplain increases as material is deposited on either side of the river.
Floodplains are often agricultural land, as the area is very fertile because it’s made up of The sediment deposited by rivers. Also known as silt. (deposited Fertile sand-sized particles found in the lower course of a river. Also known as alluvium. from a river flood). The floodplain is often a wide, flat area caused by A bend in a river. shifting along the valley.
Levees – a feature of a floodplain
- Levees occur in the The final section of a river located on flat land. of a river when there is an increase in the volume of water flowing downstream and flooding occurs.
- Sediment that has been eroded further upstream is transported downstream.
- When the river floods, the sediment spreads out across the floodplain.
- When a flood occurs, the river loses energy. The largest material is deposited first on the sides of the river banks and smaller material further away.
- After many floods, the sediment builds up to increase the height of the river banks, meaning that the channel can carry more water (a greater The volume of water in a river passing a point in a given time. Measured in cumecs (cubic metres per second).) and flooding is less likely to occur in the future.