GEOGRAPHY (rivers)

• erosion


  wearing away of rock and soil
• deposition

  when the river loses energy it drops the sediment it is carrying
• transportation

  when the river picks up and carries material / sediment
• erosion process - attrition

  when the size of rocks stones and other particles change when they are being transported they are broken down into smaller pieces by colliding with one another or with the river bed when they are travelling attrition is the main reason why pebbles on beaches are usually small and round
• erosion process - hydraulic action

  The wearing away of the surface by the force of moving water in rivers, water washes against the bed and sides in them away in time
• erosional process - abrasion

  wearing away of the surface of the rivers bed by rocks which are transported by rivers
• erosion process - solution (corrosion)

  The dissolving of certain materials in the water chemicals in the water dissolve minerals in the rocks causing them to break up
• transportation process - traction

  heavy rocks and boulders are rolled along the river bed
• transportation process - saltation

  Small stones and pebbles are bounced along the rivers bed
• transportation process - suspension

  Very small particles of sand or clay that are held up in the water these will settle overtime making the water clear
• process of transportation - solution

  Takes place when material is dissolved in water it is invisible and does not colour the water
• upper course of the river (source)

  small narrow

  steep

  lots of erosion

  vertical erosion
• at the source…


  more land

  narrow valley

  rapids

  waterfalls

  large rocks

  v shape valley
• middle course of the river

  mountains

  starts to meander

  lateral erosion
• at the middle of the river…

  meanders

  flooding

  farmland

  floodplains
• lower course of the river (mouth)

  reaches flat land

  flows slowly to start

  but then picks up speed due to friction

  huge meanders

  wide and flat
• at the lower course of the river…

  wide valley

  fast flowing

  deep water

  flat land

  estuary
• The bradshaw model

  theory which shows how the size of the river affects the stream flow

  
• cross section

  River gets wider as it erodes through the landscape as it moves downstream (lateral erosion)
• velocity (speed)


  increases towards the mouse, no friction free flowing
• stone size

  larger more angular at the source due to less erosion
• discharge (amount of water)

  more water is fed into the main channel via tributaries
• gradient

  source in the mountains, leaves mountains and enters flat land
• wetted perimeter (how much water the river can hold)

  the length of the rivers bed and banks in contact with the water increases due to more water from tributaries
• turbulence / friction

  shallow depth at source more load (sediment)
• depth

  more water and erosion of channel bed and banks allows for a large carrying capacity
• stone angularity

  large, angular boulders at the source due to limited erosion, more erosion as move downstream resulting in smaller rounder sediment
• width

  source in mountains, resulting in vertical (downwards) erosion as the river leaves the mountains lateral (sideways) erosion is possible widening the river channel
• what is the drainage basin referred to as? 


  closed system as the water never leaves instead it’s recycled from one state to another
• confluence

  where 2 rivers meet
• watershed

  an area of high land between two drainage basins
• tributary

  a small river or stream flows into a larger one
• drainage basin

  the area drained by a river and its tributaries
• inputs

  how water is introduced into the drainage basin system
• stores

  how water is stored or held for a period of time within a drainage basin system
• flow

  a process or flow of water from one place to another in the drainage basin system
• outputs

  how water is released either back into the sea or back to the atmosphere
• drainage basins

  example of a diagram:

  
• Terms to know for the exam


  • Infiltration: Water soaks or filters into the soil
  • Surface runoff: Water moves across the surface of the earth becoming a stream, tributary or river
  • Interception: water is stopped from reaching the ground by vegetation
  • Precipitation: An input where water is introduced to the drainage basin system
  • Evaporation: When water is heated by the sun and rises into the sky as water vapour
  • Transpiration: Water vapour is evaporated from the trunk and leaves of trees and other vegetation, back into the atmosphere
  • Throughflow: Water moves downhill through the soil
  • Base flow/groundwater flow: Water moving slowly through the soil and permeable rocks to move back towards the sea
  • Percolation: Water moving from the soil into the spaces (pores) in the rock
• meander

  bend in the river

  occurs in the middle and lower course where the water is moving more slowly