geography rivers

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geography rivers
2010-05-02 11:44:00

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  1. Upper course (steep gradient)
    • Vertical (downward) erosion
    • Source; Tributaries; V-Shaped valley; Interlocking spurs; Waterfalls; Rapids; Gorges
  2. Middle course (gentle gradient)
    • Lateral (sideways) erosion starts; Transportation
    • River beaches (slip off slopes); Meanders; River cliffs
  3. Lower course (very low gradient)
    • Deposition
    • Flood plain; Ox-bow lakes; LevĂ©es; Delta; Estuary
  4. * Corrasion
    - Wearing away of the river bed and banks by the load hitting against them.
  5. * Attrition
    - Wearing down of the load as the rocks and pebbles hit the river bed and each other.
  6. * Hydraulic Action
    - Breaking away of river bed and banks by the sheer force of the water getting into small cracks.
  7. * Chemical Action (Corrosion)
    - Water dissolves minerals from the rocks and washes them away.
  8. * Traction -
    Quite large stones can be rolled or dragged along the river bed by the force of the water.
  9. * Saltation
    - Small stones which the water cannot lift bounce off each other and are carried forward by the water above the river bed for short distances.
  10. * Suspension
    - If particles are small enough the river can lift them and carry them long distances.
  11. * Solution
    - When the river dissolves minerals from the rocks they are carried in the water itself.
  12. formation of a waterfall
    • (a) River flows over an area where there are bands of softer and harder rocks,
    • (b) softer rock is more quickly eroded,
    • (c) the river undercuts the harder rock leaving an overhang,
    • (d) the river forms a plunge pool below the waterfall,
    • (e) overhanging rock is unsupported and falls into the plunge pool,
    • (f) the waterfall is moved upstream,
    • (g) as this process continues a gorge is cut back into the hillside.
  13. formation of a vshaped valley
    • the valley sides are steep so fragments of rock fall into the river by gravity
    • the river has lots of energy in it's upper course and cuts downwards into the river bed by hydraulich action. the rocks it carries erode the bed banks by abrasion