Geography Revision

Formation:

1. Form where alternating pools (areas of deep water) and riffles (areas of shallow water) develop at equally spaced intervals across the river bed. 

2. Pools are more efficient, so have greater energy and so have more erosive power.

3. As a river moves over a riffle it loses energy due to friction.

4. The spacing between pools and riffles results in the rivers flow becoming uneven and maximum flow is concerntrated onto one side of the river.

5. Turbulence increases in and around pools as the velocity increases, so the flow of the water begines to twist and coil.

6. This results in corkscrew like currents in the river called helicoidal flow, which spiral from bank to bank between pools.

7. The helicoidal flow causes more erosion and deepening of the pools. 

8. The eroded material is carried and deposited on the inside of the next bend, where the river loses energy.

9. The continued combination of erosion and depostion exaggerates the bends until large meanders are formed. 

10. Oxbow lakes are formed when the neck of the loop of a meander is broken through, during flooding. Deposition occurs, leaving an oxbow lake.