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Source: images.google.com

FLOODPLAIN LANDFORMS

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What the syllabus says ….

Explain the stream channel processes (erosion, transport, deposition) and explain the resultant landforms found on floodplains.

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Task

  • Use p.121-122 ‘Course Companion’ and Geography IB Study Guide to add notes to explain the formation of each of the floodplain landforms. Include clear reference to the stream channel processes (erosion, transport and deposition)

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Features of rivers in the floodplain

  • The river now has a high volume and a large discharge in its lower course
  • The river channel is deep and wide
  • The landscape around the river is flat
  • The river will eventually slow down (energy level low)
  • Deposition takes place

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1. Floodplain

Source: www.images.google.com

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Floodplains

  • The river now has a wide floodplain
  • A floodplain is the area around a river that is covered by water in times of flood
  • A floodplain is a very fertile area due to the rich alluvium (a fine-grained fertile soil consisting of mud, silt, and sand deposited by flowing water on flood plains, in river beds, and in estuaries deposited by floodwaters . Source: www.the free dictionary.com)
  • This makes floodplains a good place for agriculture
  • A build up of alluvium on the banks of a river can create levees, which raise the river bank

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2. Meanders

  • A meander is a bend in a river. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley. The inner part of the river has less energy and deposits what it is carrying.
  • Slip off slope: long, low, gentle slope on the inside of the downstream face of a stream meander.

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Slip off slope / point bar:

long, low, gentle slope on the inside of the bend of a meander,

made of sand and gravel that accumulates as river flow is slow.

River cliff:

Steep part of the outer bend of a river, formed as erosion undercuts the bank.

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CROSS – SECTION OF A MEANDER

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3. Ox-bow lake

  • An oxbow lake is a U-shaped body of water formed when a wide meander from the main channel of a river is cut off to form a lake.

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Oxbow lakes

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4. Levees

  • Raised river banks found on a flood plain
  • Formed over time due to successive flooding of a river
  • Natural features which provide some flood defense
  • They are often raised and strengthened by humans to give extra flood protection

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Formation of levees

Source:www.web.mst.edu

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Formation of levees

Source: www.bbc.co.uk

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5. Terraces

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Source: http://murchiepages.weebly.com/

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EXAM QUESTIONS

  • Using annotated diagrams compare and contrast the processes leading to the formation of two floodplain landforms.
  • Explain how both erosion and deposition can lead to the formation of floodplain landforms.

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