River processes and River Features.

Key terms on River Processes and River Features

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  • Created by: tybeany88
  • Created on: 26-09-13 17:13
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  • River processes
    • Erosion
      • Abrasion
        • Rocks: Carried along river - wear down banks and beds
        • Works when river has lots of energy.
        • Large particles produce: rapid erosion. Smaller: smooth surfaces
      • Hydraulic Action
        • When water wears riverbank
        • Moving water - frictional drag - dislodges particles
        • Faster on the outside of a meander, undercuts riverbank - creates river cliff
      • Attrition
        • Rocks carried along the river smash into each other - becoming smaller and smoother
      • Solution
        • Some river water can be slightly acidic
        • Particles that have dissolved in the water
        • Effective on carbonated rocks - limestone
    • Transportation
      • Solution
        • Particles and minerals dissolved in water
      • Suspension
        • Fine light material carried along river - SUSPENDED LOAD (largest proportion of rivers total load)
      • Saltation
        • Small stones picked up and dropped, bounce along river bed - becoming smaller
      • Traction
        • Boulders and large rocks - rolled along riverbed
      • Influences on a rivers load
        • Capacity - total load a rver is capable of carrying
          • Increases with discharge, measured by vol, mass, or weight
        • Competence: maximum load - increases downstream - velocity and discharge increase
        • Hjulstorm graphs
      • Deposition
        • Occurs when a river loses energy and can no longer transport material
        • River enters shallow water
        • Volume of water decreases
        • Velocity is reduced
        • Load is increased
    • Deposition
      • Occurs when a river loses energy and can no longer transport material
      • River enters shallow water
      • Volume of water decreases
      • Velocity is reduced
      • Load is increased
    • River Features
      • Caused by Erosion
        • V-Shaped Valleys
          • Weathering and Erosion attacks the valley forcing it to retreat
        • Interlocking Spurs
          • Areas of hard rock that the river did not erode
        • Potholes
          • active corrasion in areas with turbulent and high velocity flow
        • Waterfalls
          • resistant rock overlies soft rock in steep areas - undercut of soft rock. resistant rock on top becomes too heavy and collapses
        • Rapids
          • Bedrock more resistant to erosion
      • Caused by EROSION and DEPOSITION
        • Meanders
          • Oxbow Lakes
            • One meander catches up with the next. Cutting off the meander - causing river to become straight.
            • Meander abandoned.
          • Large bends in river channel. high volume of water.
          • More velocity on outside bend, erodes river bank. undercutting.
          • Inside bend, velocity is reduced. Deposition of material that the river eroded earlier on
      • Caused by Deposition
        • Braiding
          • network of small channels separated by small islands
          • Main channel - straight; Sediment load is high and made of gravel and coarse sand.
          • Frequent variable and rapid discharge
        • Levees
          • Banks of silt where rivers keep flooding. - builds up over time
        • Flood Plains
          • areas surrounding river - flat and fertile good for agriculture
        • Deltas
          • Bird's Foot
            • Mississippi river: USA
            • Splits, river extends like the foot of a bird.
          • Cuspate
            • Land sticks out of the sea like an arrow.
            • Ebro in Spain
          • Arcurate
            • Creates a fan effect. River splits many times. Curving shoreline.
            • Nile in Egypt
          • Mouth of the river; many distributaries
            • River meets sea; sea is calm; river carrying a large load; material deposited faster than sea can remove it
  • Erosion
    • Abrasion
      • Rocks: Carried along river - wear down banks and beds
      • Works when river has lots of energy.
      • Large particles produce: rapid erosion. Smaller: smooth surfaces
    • Hydraulic Action
      • When water wears riverbank
      • Moving water - frictional drag - dislodges particles
      • Faster on the outside of a meander, undercuts riverbank - creates river cliff
    • Attrition
      • Rocks carried along the river smash into each other - becoming smaller and smoother
    • Solution
      • Some river water can be slightly acidic
      • Particles that have dissolved in the water
      • Effective on carbonated rocks - limestone
  • Capacity - total load a rver is capable of carrying
    • Increases with discharge, measured by vol, mass, or weight

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