rivers

• drainage basin


  area of land drained by a river and its tributaries
• skibidi toilet

  A) Fastest

  B) Vertical

  C) deposition

  D) V-shaped

  E) Meanders

  F) Oxbow

  
• erosion is the wearing away of river beds and banks
• Hydraulic action is the force of the water hitting the river banks. faster flowing water has more hydraulic power
• abrasion is when stones carried by the river scrape away at the river bed and banks
• solution is when slightly acidic rain water dissolves alkaline rocks such as limestone
• attrition is when stones within the water knock into eachother and become smaller and rounder
• suspension is when mud and fine particles float in the water and are carried in the river
• traction is when heavy boulders are rolled along the river bed
• saltation is small stones bouncing as they are moved by the rievr
• deposition is when a river deposits the load it is carrying when the flow of water slows down.
• When is deposition likely to happen?

  When the river meets an obstacle

  When it meets meanders

  When it meets the sea
• The river tees is located in north east england
• The River Tees source is Cross Fell
• Cross Fell receives 2000mm+ rainfall per year
• The upper course of the River Tees has many interlocking spurs, waterfall, gorge
• The middle course and lower course has many meanders
• The lower course has ox-bow lakes and levees
• The river Tees has an 800m long gorge
• The high force waterfall is 20m high and has hard rock called dolerite and soft rock called limestone
• physical causes of flooding:

  -precipitation

  -geology

  -relief
• human causes of flooding:

  -urbanisation

  -deforestation

  -agriculture
• a hydrograph displays rainfall as a bar graph in mm, discharge as a line graph in cumecs and peak discharge, the base flow is normal river discharge
• Dams/ reservoirs are physical barrier built across a river. THe lake created behind a dm is a reservoir
• Benefits of dams/resevoirs

  • flow can be controlled
  • can be combined with other projects
• Disadvantages of dams/ reservoirs

  • very expensive
  • large area flooded
• Channel straightening is when meanders are cut off and a straight channel is built
• benefits + costs of channel straightening:

  • water channel flows quickly before flooding can happen
  • expensive maintenance
  • flood risk increased downstream
• flood plain zoning is when land next to the river is organised into different zones, different land uses in each zone moving away from the river
• Benefits of flood plain zoning:

  • valuable land located in areas unlikely to flood
  • no interference with natural processes
• Costs of flood plain zoning:

  • difficult to stop
  • doesn't stop flooding
• Afforestation is planting trees in the drainage baisin
• Benefits of afforestation

  • interception reduces surface run-off
  • cheap
  • adds to biodiversity
• Drawbacks of afforestation

  • takes a long time to have an effect
• How are meanders formed?

  Meanders often occur in the middle course of a river as the water begins to move at a faster pace. As the water flows around a bend it is pushed towards the outer bank of the curve and this increases the levels of erosion, both abrasion and hydraulic action. As the erosion continues the lower parts of the bank begin to undercut and create a river cliff. On the inside bank of the bend water moves much slower and there is much less energy therefore deposition occurs as the water can no longer carry the sediment - the build up of this sediment is called a slip-off slope.
• Formation of ox-bow lakes:

  Continued erosion and deposition means the bend in the meander gets bigger over time. This causes the meander to be cut off from the river due to the erosion taking place on the outside bend, the deposition seals of the meander
• When flood plains are flooded, the river deposits fine sediment that gradually builds up the flood plain
• Levees are natural embankments on either side of the river. They are formed when the river floods and deposits the large material it's carrying next to the river channel
• Estuaries are formed when freshwater and seawater mix, which causes the river to deposit sediment and causes mudflats
• interlocking spurs are formed in the upper course when a river winds around bands of a more resistant rock