3.3.3 Fluvial Landforms - Caused by Deposition

Floodplains

Estuary

• Where the river meets the sea.
• The river here is tidal; when the sea retreats, the volume of water in the estuary is reduced.
• When there is less water, the river deposits silt to form mudflats, which are important habitats for wildlife.
• The land of an estuary is not very fertile, making it unsuitable for agriculture.
• Estuaries create good habitats for wildlife.

Estuary

Delta

• Found at the mouth of large rivers (e.g., the Mississippi).
• Formed when the river deposits material faster than the sea can remove it.
• As the river approaches the sea, it loses energy and deposits material.
• Sediment may be sorted, with the heaviest material deposited first.
• Over time, more sediment is added, building up a land mass (delta) at the mouth of the river.
• Strong tides can wash away sediment; if not, it will accumulate to form a delta.

Levees

• Natural embankments along the edges of a river.

• During a flood, eroded material is deposited over the whole floodplain.

  

• Heaviest material is deposited closest to the river channel as the river slows down.

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