Songhua River,
northeast China. Swirls and curves, showing paths the river once took, as well as oxbow lakes, are easily seen in this satellite photo.
An 'oxbow lake' is a U-shaped
lacustrine water body formed when a wide
meander from the
mainstem of a
river is cut off to create a lake. This
landform is called an oxbow lake for the distinctive curved shape that results from this process. In
Australia, an oxbow lake is called a
billabong.
Formation
When a river reaches a low-lying plain in its final course to the
sea or a
lake, it
meanders widely.
Deposition occurs on the bank (known as a
point bar) because of the ‘slack water’, or water at low velocity. In contrast, both lateral
erosion and undercutting occur on the concave bank (or
cut bank) where the stream’s velocity is the highest. Continuous erosion of a concave bank and deposition on the
convex bank of a meandering river cause the formation of a very pronounced
meander with two banks getting closer. The narrow neck of land between the two neighbouring concave banks is finally cut through, either by lateral erosion of the two concave banks or by the strong currents of a
flood. When this happens, a new straighter river
channel is created and an abandoned meander loop, called a cut-off, is formed. When deposition finally seals off the cut-off from the river channel, an oxbow lake is formed. This process can occur over a time scale from a few years to several decades and may sometimes become essentially static.
A Horseshoe or oxbow lake near
Hughes, Arkansas,
USA.
The bulges in the border reflect changes in the course of the river; when the river shifted its course and cut off the former channel, the border did not change.
By itself, the word oxbow can also mean a U-shaped bend in a river or stream, whether or not it is cut off from the mainstream.
[1][2]
Examples
Early stages of formation of coastal plain ox-bow lake. Gower Peninsula, Wales, UK
The
Reelfoot Lake in west
Tennessee is an oxbow lake formed when the
Mississippi River changed course following the
New Madrid Earthquake of
1811–
1812. There are many oxbow lakes alongside the Mississippi River and its tributaries. The largest oxbow lake in North America,
Lake Chicot (located near
Lake Village, Arkansas), was originally part of the
Mississippi River.
The town of
Horseshoe Lake, Arkansas is named after the horseshoe shaped oxbow lake at the estern tip of which the town is located.
Cuckmere Haven in
Sussex,
England contains a widely
meandering
river with many oxbow lakes, often referred to in
physical geography textbooks.
Notes
1. Ask Oxford.
2. Merriam-Webster.
References
★
NASA Remote Sensing Tutorial: Fluvial/Deltaic/Coastal Landforms
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