RIVER LANDSCAPES

• drainage basin


  an area drained by a river and its tributaries
• upper course

  • starts as many narrow and v shaped tributaries
  • large gradient
• middle course

  • tributaries merge to form a channel
  • higher volume of water
  • more erosion, so channel widens
• lower course

  • carries largest volume of water
  • wide and flat channel
• erosional landforms - interlocking spurs

  • upper course
  • water isn't strong enough to erode resistant rock in spurs so the water flows around them
• erosional landforms - waterfalls

  • soft rock erodes faster than hardrock
  • soft rock erodes and undercuts the hard rock, leaving it as an overhang
  • plunge pool forms
  • unsupported overhang collapses and aids erosion of plunge pool
  • continual process of overhang collapsing causes waterfall to move upstream
• erosional and depositional landforms - meanders

  • water travels faster on outside of bend(thalweg) so lateral erosion takes place
  • inside of bend water travels slowly and has less energy so deposits sediment, forming a slip-off slope.
• erosional and depositional landforms - ox-bow lake

  • erosion of meander bends the necks towards each other
  • necks break forming a straight river
  • old meander becomes separated from river, creating an ox-bow lake
• depositional landforms - floodplains

  • large meanders grow outward and flood
  • water looses energy and deposits its load
• depositional landform- Levee

  • banks of river in lower course
  • every time the river floods sediment is deposited onto the banks
• depositional landform - estuaries

  • mouth of a river
  • river flow is disrupted and slowed by tides so there's a large amount of deposition which creates mudflats and salt marshes
• RIVER TEES

  • NE England

  LANDFORMS

  • high force waterfall
  • meanders
• human factors effecting flood risk

  URBANISATION

  • increasing amount of impermeable surfaces causes increased surface run off

  DEFORESTATION

  • vegetation doesn't take in water or slow down the time it takes for water to reach rivers
• physical factors effecting flood risk

  GEOLOGY

  • impermeable rocks means water cant infiltrate into soil and be stored underground

  PRECIPITATION

  • large amounts of rain in a short time increases flood risk
• flash flood

  • flood with little warning, where large volumes of water overwhelm the river
  • large amount of rain in short period
• subdued flood

  • prolonged period of consistent rain
• drainage basins - soft engineering - floodplain zoning

  • constructing houses further from river
  • reduces damage without altering river
  • only for new developments
• soft engineering - wetlands

  • vegetation planted
  • store water and can be flooded without damaging houses
  • creates valuable habitats but takes a long time to grow
• hard engineering - dams

  • concrete blockade stores water in upper course and regulates river flow
  • controls water flow but is expensive and unattractive
• hard engineering - embankments

  • banks built up in brick and concrete to increase channel capacity
  • reduces lateral erosion but looks unnatural
• hard engineering - dredging

  • rubbish and sediment dug up from bottom of river
  • widens channel and cheap
• BANBURY FLOODING

  • River cherwell
  • 1998
  • £12.5 million
• reducing floodrisk after banbury flooding

  • roads built higher up
  • flood water storage schemes
  • embankments and flood walls built
• social

  • reduces anxiety about floods
  • raised roads mean people can continue with their daily lives

  economic

  • £18.5 million scheme
  • benefits of protecting buildings saves a potential £100 million

  environmental

  • increased biodiversity