geography rivers

  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
Card Set
geography rivers