Processes forming river landscapes

V-shaped valley

Formation of a V shaped Valley

Formation of a V-shaped valley

  • Rivers begin high up in the mountains so they flow quickly downhill eroding the landscape vertically.
  • The river cuts a deep notch down into the landscape using hydraulic action, corrasion and corrosion.
  • As the river erodes downwards the sides of the valley are exposed to freeze-thaw weathering which loosens the rocks (some of which will fall into the river) and steepens the valley sides.
  • The rocks which have fallen into the river help the process of corrasion and this leads to further erosion.
  • The river transports the rocks downstream and the channel becomes wider and deeper creating a V-shaped valley between interlocking spurs.

Erosion

Waterfall

Formation of a waterfallFormation of a waterfall

  • The river flows over bands of softer and harder rocks.
  • Softer rock is more quickly eroded.
  • The river undercuts the harder rock leaving an overhang.
  • The river forms a plunge pool below the waterfall.
  • Overhanging rock is unsupported and falls into the plunge pool.
  • The waterfall is moved upstream.
  • This process continues and a gorge is cut back into the hillside.

Waterfalls, plunge pools and potholes

Meander

Formation of a meander Formation of a meander

  • Water twists and turns around stones and other obstructions resulting in areas of slower and faster water movement.
  • The river starts to flow from side to side in a winding course but still in a relatively straight channel.
  • Water moving faster has more energy to erode; this occurs on the outside of the bend and forms a river cliff.
  • The river erodes the outside bends through corrasion, corrosion and hydraulic action.
  • Water moves slowly on the inside of the bend and the river deposits some load, forming a river beach/slip-off slope.
  • Continuous erosion on the outer bank and deposition on the inner bank forms a meander in the river.
  • The meander will migrate downstream and change shape over time.

Meanders