Explain the formation of an Ox-Bow Lake
A typical river formation question would be:
Explain the formation of a *.
You may wish to use an annotated diagram in your answer (8)
*The features you can be asked are:
Waterfalls
V-shaped valleys
Meanders
Ox-Bow Lake
Meanders & Oxbow Lakes form in the middle and lower courses, where the valley is wide enough for lateral erosion to occur.
Over time, they become more pronounced and can change the course of rivers.
Digital Workbook and Paper Jotter
Draw the annotated diagram for the feature
Write out the explanation under each
Fully explained processes will gain you double marks. 1 mark for naming the process and 1 for explaining the term but you NEED to do both to get both marks.
*some marks can also be given the explanation of the formation of a meander*
A river meanders across the valley eroding laterally(1)
Water directed at the outside of the bend has reduced friction and increased velocity(1).
The faster-flowing water erodes through Hydraulic action(1) when air is compressed into the river bank causing materials to be dislodged(1) and Abrasion(1), pieces of broken-off rock thrown at the river bank causing erosion(1).
There is less water on the inside bend, so less energy means the material is deposited creating a river beach. (1)
Over time continued erosion and deposition narrow the neck of the meander. (1)
During a time of peak discharge (during a flood), the river will break through the neck continuing on a straight path(1), abandoning the meander.
The fastest current is now in the centre of the straight channel and deposition will occur at the side of the river banks. (1)
This deposition will seal off the ends of the meander leaving Oxbow Lake (1). This will eventually dry up and disappear except during times of heavy rainfall or flooding.