River Landscapes

• Hard engineering examples: 


  Dams and reservoirs, channelisation
• Soft engineering examples:

  flood plain zoning, Washlands
• Upper course of river

  • Relatively high above sea level
  • More gravitational potential energy
  • Vertical (downwards) erosion dominates
• Middle and lower courses of river

  • Relatively low
  • Erodes more laterally (side to side)
• Water joining river


  1. From tributary streams

  2. Surface runoff

  3. Through flow

  4. Base flow
• River velocity


  Affected by how efficient the river is in overcoming friction with bed and banks
• Sediments


  • Become smaller and rounder due to attrition
• Deposition creating river landforms

  1. Flood plains

  2. Levees
• Flood plains


  • Lateral erosion on the outside bends of meanders
  • Valley floor becomes more wide and flat
  • During floods, the flood waters spread out across the valley floor
  • As they slow down with less energy for transport, the river deposits fine sediments called alluvium
  • Flood waters move very slowly, because they counter in friction
• Levees


  • In times of flood, water and sediment come out the channel as the river overflows its banks
  • As it overflows the river immediately releases velocity, energy and deposits the larger and heavier sediment first, on its banks
  • Repeated flooding causes these banks to get higher forming levees
• Erosion and deposition creating river landforms

  1. Meander, river cliffs and point bars

  2. Oxbow lakes
• Meander, river cliffs and point bars

  • As water approaches a meander it is thrown towards the outside of the bend
  • Current is faster here and erosion occurs to form a river cliff
  • On the inside of a bend a current is slower and deposition occurs due to increased friction
• Oxbow lakes


  • Meander is being eroded
  • Water takes the quickest route
  • Deposition takes place cutting off the meander
  • Meander rock cut off completely
  • Oxbow lake is left behind
• Physical causes of flooding in Loughton Brook drainage basin

  • Impermeable Geology
  • Steep slopes
  • Small drainage basin
• Impermeable Geology


  Reduces infiltration and accelerates surface run-off
• Steep Slopes


  Speed up run-off into the river
• Small Drainage Basin


  Drainage is faster because of the small size
• Human causes of flooding in Loughton Brook drainage basin

  • Deforestation
  • Urbanisation
• Deforestation


  • Reduces infiltration because the soil becomes more compact and rainwater reaches the surface faster
  • Interception is reduced
• Urbanisation


  • Spreads impermeable surfaces (less infiltration)
  • Many drains to quickly transport rainwater into the river
• Dams and reservoirs and how they work

  barriers constructed to hold back water
• Dams and reservoirs benefits and advantages

  They are long-lasting also produce hydro-electric power, provide local water supply. Can be used for water sports
• Dams and reservoirs costs and disadvantages

  They are expensive to build and can cause the displacement of people and ruin the environment. Some lakes suffer from the growth of Algae
• Channelisation Costs and disadvantages:

  Water taken downstream may put other places at risk. It doesn't look natural.
• Channelisation benefits and advantages 


  This involves more water to run through more quickly taking it away from places at risk concrete reducing friction increasing velocity.
• Channelisation and how it works

  this involves deepening and or straightening the river.
• Flood plain zoning and how it works

  governments allocate areas of land to different uses according to their level of flood risk.
• Flood plain zoning Benefits and advantages

  Food risk management aims to prevent building homes and businesses for leisure and recreation are allowed because of flooding
• Flood plain zoning Costs and disadvantages

  These may not be for the best places for different activities in terms of public accessibility
• Washlands and how they work

  areas on the flood plain are allowed to flood
• Washlands Costs and disadvantages:

  Allowing land to flood may limit use of land for recreation for example or mean change of land use, for example a change of farmland
• Washlands Benefits and advantages:

  give a safe place for floodwater to of and help slow floodwaters down. Also improves a river natural sediment process