Geography rivers

• Traction

  The large stones are rolled around the bed of the river
• Suspension

  Light material like sand and silt are carried along (floating) in the water
• Saltation

  The smaller pebbles are bounced along the bed of the river
• Solution

  Dissolved materials are carried along the river
• Deposition

  When a river can no longer carry its load (the material it is carrying and it ‘drops’ the material)
• Deposition - main reason

  The river loses Velocity this can happen because

  • decrease in the gradient
  • decrease in river flow (discharge) as water drains away after heavy rainfall
  • river meets the sea or the lake
  • flows more slowly on the inside of bends
• Discharge

  This is the volume of water flowing down the river at any one time. It is measured in cubic metres per seconds (cumecs)
• Evaporation

  Change of water from a liquid to a gas
• Condensation

  Change of water from a gas to a liquid
• Precipitation

  Water falling from the sky (e.g. Rain, sleet, hail, snow)
• Transpiration

  Release of water vapour from the leaves of trees of plants
• Watershed

  Dividing line which seperates 2 adjacent drainage basins/catchment area

  
• Mouth

  End point of a river where it enters the sea

  
• Tributary

  smaller river joining a bigger river

  
• Confluence

  Point where a tributary meets the main river

  
• Source

  Place where the river begins, usually in an upland area. From spring, melt water from glacier, or swampy area

  
• Upper course

  • Vertical erosion with Hydraulic action, abrasion & attrition dominant processes
  • Traction and saltation at high flow
  • Load size is large and angular
  • V shaped valley

  
• Middle course

  • Channel is deeper and wider
  • Vertical erosion decreasing in importance. More lateral erosion and deposition
  • suspension is the main transportation type
  • Load becomes smaller and less angular

  
• Lower course

  • Channel is at its widest and deepest - may be tidal
  • Deposition more important than erosion
  • fine material deposited
  • large amount of load but the size is very small nd very rounded

  
• Hydraulic action

  • Smashes against river banks
  • air becomes trapped in the cracks of the river bank and bed causing rock to break apart
• Abrasion

  Pebbles grind along the river bank and bed in sand papering effect
• Attrition

  • When rocks that tje river is carrying knock against each other
  • They break apart to become smaller and more rounded

  
• Solution

  When the water dissolves certain types of rocks like limestone

  
• 3 types of deltas

  • fan shaped
  • cuspate
  • birds foot
• Delta can only form when

  • river is transporting large amount of sediment
  • sea must have a small tidal range and weak currents
  • sea must be shallow at river mouth
• Levees

  Lower course river widens valley through lateral erosion.

  High discharge provides energy for material transportation in suspension.

  River overflow results in spreading over a flat surrounding area.

  Increased friction during overflow reduces river velocity, causing deposition of sediment (silt).

  • Coarsest material deposited first, forming a natural embankment (levee) next to the river.
• Rapids

  • Rapids stretched of fast-flowing water tumbling over a rocky-shallow river bed
  • formed when water goes from one hard rock that resists the waters erosion to a softer rock that is eroded easier.
  • Over time, rapids are formed