Meanders

Photographs of meanders

In the middle course the river has more energy and a high volume of water. The gradient here is gentle and lateral (sideways) erosion has widened the river channel.

The river channel has also deepened. A larger river channel means there is less friction, so the water flows faster.

Illustration showing erosion and deposition in a river The formation of a meander.
  • As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
  • The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.
  • The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy due to decreased friction. This will form a river cliff.
  • On the inside of the bend, where the river flow is slower, material is deposited, as there is more friction. This will form a slip-off slope.
  • Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through, e.g. during a flood when the river has a higher discharge and more energy, and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake.

Meander cross section

Cross section through a meander