River depositional landforms

what is a flood plain

flat low lying areas of land on either side of the river which ocassionally get flooded

How do flood plains form?

1. Lateral (sideways) erosion in the lower course

• The river is wide and fast-flowing in the lower course.

• It erodes the sides of its valley (not just the bottom).

• This makes the valley wider and flatter.

2. River floods and spills over the banks

• When the river floods, water spreads across the surrounding land.

• As the water slows down, it loses energy and deposits sediment (like silt and sand).

how are floodplains built up

1. . as meanders migrate downstream they flatten out the valley floor and make the flood plain wider, the deposition that happens on the slip off slopes of meanders also builds up the flood plain

what are levees

Natural embankments (raised bits) along the edges of a river channel

how do levees form

-During a flood, eroded material is deposited over the whole flood plain

-Heaviest material is deposited closest to the channel because it gets dropped first when the river slows down

-Over time, the deposited material builds up, creating levees along the edges of the channel

what are deltas

Low lying areas where a river meets the sea or a lake

how do deltas form

-Rivers are forced to slow down when they meet the sea or a lake, causing them to deposit material they're carrying

-If the sea doesn't wash away the material, it builds up and the channel gets blocked, forcing the channel to split up into lots of smaller rivers called distributaries

-Material builds up so much that low-lying areas of land called deltas are formed