Erosion

Erosion occurs in all rivers. Erosion is the wearing away of the river bed, river banks and channel. There are different types of erosion in a river:

Erosion caused by water
Running water is very powerful. The water from rivers and streams has a lot of energy when it is travelling very fast. This energy can wear away the sides and banks of a river's channel as well as the river bed. The pressure of the water can also wear away the river bed to make a V-shaped valley. Erosion from the water can create features like waterfalls and rapids which are formed by the erosion of soft rocks overlying a band of harder rock.

Erosion caused by rocks and stones in the water
When a river moves stones and rocks along its bed, the sides of the channel and the river bed are eroded. As these stones and rocks move along, they hit the river banks and the river bed, causing pieces of rock to break off. This gradually erodes the river bed and channel sides, making the river wider and deeper.

Evidence of erosion
Signs of erosion may often be seen in a river. Look for one or more of these signs:

• Exposed tree roots.
  
• Cracks in the soil in a river bank.
  
• Clumps of grass in the river.
  
• The top part of the river bank overhangs.
  
• Brown or coloured water.
  
• Collapsed river bank.

  
  The photo above shows six examples of erosion.