New Geography in Action Junior Cycle Geography Oxbow lakes
An oxbow lake is a horseshoe-shaped lake that is formed when a meander is cut off from the river.
Formation: • When the neck of a meander becomes very tight, the river can erode its way through the neck to take the straightest course.
• This usually happens during a flood when the river has a higher discharge and more energy.
• The loop is cut off from the main river when sediment is deposited at the entrances to the loop.
• The cut-off loop is called an oxbow lake. Over time, this lake will dry up and form an oxbow scar.
Examples of oxbow lakes: in the middle courses of the rivers Liffey and the Moy.
Discharge:
the flow of water downwards through a river.
81 ( Figure 9.14 Formation of an oxbow lake 40 41 42 43 81
Beginning of oxbow lake
80 80 Meander 79 79
Confluence Flood plain
: Figure 9.15 Oxbow lake in central Alaska
The old stage (lower course)
At this stage the river is nearing the end of its course. It flows slowly along flat land and carries a load that has been eroded during the previous stages and through surface run-off. As the river is now nearing the sea, it has less energy and deposition has become the main process.
78 78 3 Oxbow 2 1
Loop cut off
Neck of meander
77
77
76 40 41 42
76 43
: Figure 9.16 Landforms of the mature and old stages of a river on an OS map
Why do you think there are trees planted along the course of the river in Figure 9.16? Discuss in pairs. ACT VITY
