Landscapes and Processes

• types of erosion that occurs within rivers

  hydraulic action, abrasion, attrition, solution
• describe hydraulic action


  This is the sheer power of the water as it smashes against the river banks. Air becomes trapped in the cracks in the rock of the river bank and bed, and causes the rock to break apart
• describe abrasion

  When pebbles grind along the river bank and bed in a sand-papering effect
• describe attrition


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

  When the water dissolves certain types of rocks, eg limestone
• 4 types of transportation

  Traction

  Saltation

  Suspension

  Solution
• desribe traction

  large, heavy pebbles are rolled along the river bed
• describe saltation

  pebbles are bounced along the river bed, most commonly near the source.
• describe suspesion

  lighter sediment is suspended (carried) within the water,
• describe solution


  the transport of dissolved chemicals
• describe deposition

  when a river loses energy, it drops any of the material it has been carrying. factors include : shallow water, at the river's mouth, when the volume of the water decreases
• describe formation of interlocking spurs

  river can't erode laterally due to hard rocks, so winds around, forming interlocking spurs
• describe formation of meanders + oxbow lakes


  Lateral erosion creates wide bends, or meanders, in the river. If meanders grow large enough, a section of the river becomes cut off from the main channel. This leaves an oxbow lake
• how does geology affect rates of landform change?

  resistance and structure of local rock affects rates of erosion
• how does climate affect rates of landform change?


  - rivers discharge affected by rainfall. higher discharge means more power to erode

  - extreme weather events can cause significant erosion
• how does human activity affect rates of landform change?


  - urbanisation of river valley and floodplain can increase river discharge levels

  - management can have impacts
• describe formation of floodplains

  These are flat areas of land either side of a river channel. At times of high water, floodplains may be covered in water
• What is a drainage basin?

  an area of land drained by a river and its tributaries
• outline flow of water through the drainage basin

  
• infiltration

  The downward movement of water from the surface into the soil.
• surface runoff

  Water flows across the surface of the earth
• Evapotranspiration

  Water vapour is evaporated from the trunk and leaves of trees and other vegetation, back into the atmosphere.
• throughflow

  Water flows downhill within the soil.
• groundwater flow


  Water flowing slowly through rocks towards the sea.
• percolation

  The downward movement of water from the soil into the rock beneath.
• why do rivers flood?

  The river discharge in the channel increases, and spills over the banks
• impact of human factors on flooding

  - building: creates impermeable surfaces, drains also increase flow of water into rivers

  - deforestation: vegetation intercepts rainfall, slowing its movement, less vegetation leads to less interception
• causes of flooding in Somerset levels

  - CLIMATE: saturated ground due to excess rainfall

  - TOPOGRAPHY: low-lying land, very flat

  - HUMAN ACTIVITY: land has been drained, no dredging
• effects of flooding in Somerset levels

  - SOCIAL: affected houses, businesses, animals, farmland

  - ECONOMIC: houses and items ruined, insurance costs increase, cost for recovery

  - ENVIRONMENTAL: crops ruined, soil severely damaged
• weathering processes that act on coasts

  - mechanical: salt weathering, freeze thaw weathering

  - chemical: carbonation

  - biological: flora and fauna weaken rock
• erosional processes along coastlines


  - hydraulic action; waves crash along base, air and water pushed into joints, gaps and cracks widen

  - abrasion: rocks and pebbles hitting cliff
• describe formation of headlands and bays

  Headlands are usually formed of more resistant rock types than bays.

  If there are different bands of rock along a coastline, the weaker or softer rock, such as clay, is eroded fastest. This leaves more resistant rock types, such as granite, sticking out.
• formation of beaches


  -beaches are accumulations of sand and shingle,formed by deposition
• rockfall


  fragments of rock break away from cliff face
• landslide


  blocks of rock slide downhill
• mudflow


  saturated soil and weak rock flows down a slope
• rotational slip


  slump of saturated soil and weak rock along a curved surface
• hydraulic action


  waves crash along base, air and water pushed into joints, gaps and cracks widen
• abrasion

  rocks and pebbles hitting cliff
• strata

  layers of rock