An oxbow lake is a type of lake which is formed when a meander from a stream or a river is cut off to form a lake. They are called oxbow lakes due to the distinctive curved shape that results from this process. In Australia, an oxbow lake is referred to as 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 convex bank because of the ‘slack water’, or water at low velocity. In contrast, both lateral erosion and undercutting occur on the concave 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 concave banks getting closer. The narrow neck of land between the two neighbouring concave banks is finally cut through by either lateral erosion of the two concave banks of the strong currents during 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.

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.

Images

• Picture of a meander and oxbow lake said to be courtesy of the USGS.
• False River oxbow lake, near Baton Rouge Louisiana.
• Oxbow lakes near Zurich Montana.
• Filled in oxbow lakes, Rob-Bell Plantation near Scott Arkansas.