Topic 7: rivers and landscapes

• What does a river's long profile describe?

  The gradient
• What does a river's cross profile describe?

  The cross-sectional shape of the river bed
• Why do the long and cross profiles of a river change?

  Due to the interaction of erosion, transportation, and deposition
• What are the characteristics of the upper course of a river?

  • Steep gradient
  • Vertical erosion
  • Large, very angular bedload
  • Narrow and shallow channel
  • V-shaped channel
• What are the characteristics of the middle course of a river?

  • Gentle gradient
  • Lateral erosion
  • Smaller, more rounded bedload
  • Wider and deeper channel
  • U-shaped channel
• What are the characteristics of the lower course of a river?

  • Very gentle gradient
  • Limited lateral erosion, deposition more dominant
  • Fine sediment
  • Channel at its widest and deepest
  • Wide U-shaped channel

  
• What are the three courses of a river?

  1. Upper
  2. Middle
  3. Lower
• What is a source in relation to a river?

  Where the river starts
• What is a confluence?


  The point where two rivers meet
• What is a tributary?


  A stream that joins the main river
• What is a watershed?

  The boundary of the drainage basin
• What is a mouth in relation to a river?


  Where the river flows into the sea
• What do fluvial processes include?

  • Erosion
  • Transportation
• What is erosion?


  Sculpting and wearing away of the landscape
• What is transportation in the context of rivers?

  Movement of sediment within the river channel
• What are the two types of erosion?

  1. Vertical erosion
  2. Lateral erosion
• In which direction does vertical erosion occur?

  Downwards
• In which direction does lateral erosion occur?

  Sideways
• What are the four processes of erosion?

  1. Hydraulic action
  2. Abrasion
  3. Attrition
  4. Solution
• What is hydraulic action?

  The force of the river hitting the banks and river bed can cause air to become trapped in cracks, weakening the banks
• What is abrasion?


  Rock fragments carried by the river hit the banks and the bed, causing them to wear down
• What is attrition?

  Rocks carried by the river collide with each other, causing them to break and become smaller, rounder rocks
• What is solution in the context of erosion?

  Soluble rocks such as limestone dissolve in the river
• What are the four types of transportation processes?

  1. Suspension
  2. Traction
  3. Saltation
  4. Solution
• What is suspension in the context of river transportation?

  Particles carried within water
• What is traction?

  Rolling of large pebbles along the river bed
• What is solution in the context of transportation?

  Dissolved minerals carried within water
• What is saltation?

  Bouncing of small pebbles along the river bed
• What is deposition in the context of rivers?

  Occurs when the energy of a river decreases and it no longer has enough energy to transport material
• Where can deposition occur?

  Where the river meets another body of water at the river mouth or where water is shallower
• How do waterfalls form?

  1. Water flows over a band of hard rock that overlies a band of soft rock.
  2. Erosion processes of hydraulic action and abrasion interact to undercut the soft rock and create an overhang.
  3. Over time, the overhang collapses under the force of gravity.

  
• How does a gorge form?

  1. The process for waterfalls forming repeats over centuries.
  2. This causes the waterfall to retreat upstream.
  3. Forms a steep-sided valley known as a gorge.
• How are interlocking spurs formed?

  • Upper course → more vertical erosion -> river less powerful
  • Material not moved in suspension but using traction or saltation instead.
  • this Creates V-shaped valley.
  • Areas with hard rock ->harder to erode ->river to bends around them.

  
• What is a named example for interlocking spurs?

  Carding Mill Valley in the Shropshire Hills
• What is a named example for a gorge and a waterfall?

  Niagara gorge which is downstream from Niagara falls
• When does deposition occur?

  • When the river no longer has enough energy to transport sediment.
  • It deposits sediment.
• What are the three types of deposition landforms?

  1. Levee
  2. Flood plain
  3. Estuary
• What is a levee?

  An elevated bank along a river's edge formed when repeated flooding leads to deposition
• What is a flood plain?


  • A wide, flat area of land on either side of a river that is often subject to flooding.
  • Composed of alluvium left by deposition during floods.
• What is alluvium?


  Finer sediment