rivers

• drainage basin

  the land that is drained by a river system.
• watershed


  an imaginary line that separates one drainage basin from the next.
• source

  the starting point of the river.
• Smaller rivers join the

  main one. They are

  called tributaries.
• The point where two

  rivers join is called a

  confluence.
• Land that gets flooded when the river

  overflows is called the floodplain.
• The mouth of the river is where it flows into a lake,

  or the sea or an ocean.
• Erosion processes

  
• Traction

  Heavy rocks and boulders are rolled

  along the river bed. Happens most

  in times of flood, when the current

  is strongest.
• Saltation.

  Small stones and pebbles

  are ‘bounced’ along the river

  bed. Saltation can take

  place when the river flow is

  less than that needed for

  ‘Traction’ to take place.
• Suspension

  Very small particles of sand or

  clay that are ‘suspended’ in the

  water. These particles will ‘settle’

  if kept in a jar of water overnight

  and the water will look clear.
• Solution.

  Takes place when material is dissolved in the

  water, it is invisible and does not colour the

  water. Occurs often in limestone landscapes

  where the water is very acidic. Some

  pollutants like weed-killer are also held in

  solution in the water
• River Long profile

  
• Long profile

  
• Cross profiles

  
• Changes along long profile

  
• Downstream vs Upstream

  
• Gradient


  The change in the slope of the river bed as it passes

  from source to mouth
• Channel width


  The distance from one bank to another
• Channel depth


  The distance from the surface of the water to

  the channel bed
• Velocity


  The speed at which water is moving through the

  channel – measured in m/s
• Discharge


  The amount of water passing a given point in a

  given time – measured in cumecs

  (metres3/second) calculated by velocity x volume
• V shaped valleys and interlocking spurs

  
• Near the source, rivers do not have a lot of power as

  they are very small. They tend to flow around valley

  side slopes called spurs, rather than being able to

  erode them. The spurs are interlocking with those

  from one side of the valley with an other.
• What are interlocking spurs?

  These are projections of high land that

  alternate from either side of a valley and

  project into the valley floor.
• Characteristics of interlocking spurs

  steep gradient

  convex slopes

  project from valley side

  may have scree slopes

  form a ‘zip-like’ pattern
• Characteristics of v-shaped valleys:

  narrow

  steep sided

  have interlocking spurs
• How waterfalls are created

  
• Meanders


  A meander is a bend in the river

  Found in the middle and lower courses

  Created by lateral erosion AND deposition
• Meander cross section

  
• River bend

  
• Meander of a river

  
• Development of an ox bow lake

  
• Which part of the meander has the most erosion? Why? outside; because the water is flowing fastest
• Which part of the meander has the most deposition? Why? = inside; because the water is flowing slowest and has no more energy to carry sediment
• What landform is created on the outside of a meander? river cliff
• Which part of a meander has the shallowest water? inside
• In which course of the river do you normally find meanders? Why? middle and lower courses; land is flatter so river winds a longer
• Floodplain

  -

  
• Floodplains and levées