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Formation of Oxbow Lakes: Meandering Rivers, Erosion, and Deposition

Joseph Comunale, Mary Ellen Ellis
  • Author
    Joseph Comunale

    Joseph Comunale obtained a Bachelor's in Philosophy from UCF before becoming a high school science teacher for five years. He has taught Earth-Space Science and Integrated Science at a Title 1 School in Florida and has Professional Teacher's Certification for Earth-Space Science.

  • Instructor
    Mary Ellen Ellis

    Mary Ellen is a science and education writer with a background in chemistry. She holds an M.S. in analytical chemistry and has worked as a high school science teacher.

How is an oxbow lake formed? How does a meander becomes an oxbow lake? Discover the oxbow lake definition, and see oxbow lake examples and diagrams. Updated: 09/13/2021

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What is an Oxbow Lake?

Rivers exist across landscapes, carrying rainwater from higher altitudes down into streams, lakes, and eventually the ocean. Occasionally, there are lakes side by side with rivers and many of them are a similar curved crescent, horseshoe, or U-shape. These curved shapes are called "oxbows." What is an oxbow lake?

Oxbow lakes are the curved U-shaped lakes that exist and are created by the meandering action of a river. Rivers are rarely straight and tend to curve or snake through landscapes because of erosion and deposition. Erosion occurs when sediments are carried away, and deposition occurs when sediments are left behind.

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  • 0:00 What is an Oxbow?
  • 0:30 What is a Meandering River?
  • 1:35 When a Meander Grows…
  • 2:15 What is an Oxbow Lake Like?
  • 2:50 Oxbow Fun Facts
  • 4:05 Lesson Summary
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How is an Oxbow Lake Formed?

Oxbow lakes are created through erosion and deposition processes that occur in rivers that run through soft landscapes. The curved snaking shape of a river is called a meander. Throughout meanders there are banks along the edges where either erosion or deposition occur. Deposition occurs along the inside bank of a river's meander, where the slower moving waters leave behind sediments and rock. Erosion occurs along the outside bank of a meander where fast moving waters break up and carry away sediments. These two actions of eroding and depositing sediments along banks cause rivers to meander, and eventually create oxbow lakes through a series of steps that occur at the neck of a meander. Additionally, earthquakes can cause rivers to change course and form oxbow lakes, and sometimes rivers are artificially manipulated to follow a straighter path, forming artificial oxbow lakes near them.

Meandering River

But how exactly does a river end up meandering in the first place? Why do rivers snake through landscapes?

The meandering Jurua River in the Amazon of Brazil.

This image shows a meandering river. How does a meander become an oxbow lake? This image might provide a clue.

When rivers are flowing down from mountains, their path tends to stay same because of the hard and rocky material that guide and channel the waters down the mountain. However, once a river makes its way to a plane or a flatter landscape where there are more soil and sediments, the river becomes dynamic and changes through the processes of erosion and deposition that occur along the river's edges.

An individual meander. Deposition can be seen on the inner bank of the river.

This image shows an individual meander of a river.

There are rarely straight lines in natural landscapes, so any slight disturbance or imperfection along a straighter channel of a river will result in the flow of water slightly changing directions. For example, a slight indentation along the edge of a river created by erosion of softer material (or the action of an animal) will cause the rushing water to continue into the edges of the indentation, continuing to erode it. The more sediments are swept away, the larger the indentation gets, and more water and mass is allowed to flow through the indentation. The larger the indentation gets, the more water is diverted into the sediment, continuing to erode it. Because water is diverted to one side of the river, the water is slower on the other side of the river, opposite the indentation. Slower waters cannot carry sediments as well as fast-flowing water, so deposition begins to build up opposite the eroded indentation. A slight meander has formed.

This diagram shows how a meander forms and becomes more pronounced. It also shows where erosion and deposition occur along a meander.

This diagram shows how a meander forms and becomes more pronounced. But how does a meander become an oxbow lake?

The fast-moving water along the newly-formed outside bank sweeps out of the indentation and continues its path, carrying its momentum across the channel and slamming into the opposite bank, where it begins to erode another curve. Deposition then builds up opposite of this curve, and the process continues. But how does a meander become an oxbow lake?

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Frequently Asked Questions

What are the three oxbow lakes?

There are more than three oxbow lakes in the world. So there are no "three" oxbow lakes. But it is possible to summarize the formation of an oxbow lake in three steps:

(1) A river meanders, and erosion and deposition make the meanders more pronounced. (2) Two sides of a meander or two erode toward each other until the neck of land between them is eroded away, and the river follows a new path. (3) Deposition builds up along the banks between the river channel and its former meander, eventually cutting the meander off from the river channel completely, forming an oxbow lake.

What do you mean by oxbow lake?

An oxbow lake is a U-shaped lake that was formerly a meander in an adjacent river. "Oxbow" describes the U-shape of a meander or curved, snaking path of a river. When a meander is cut off from the rest of the river, it becomes an oxbow lake.

How is an oxbow lake formed step by step?

Oxbow lakes form through the following steps:

(1) Rivers meander because of the processes of erosion and deposition, where sediments are taken away from the bank of the river forming a curve, and deposited on inside banks due to slower flowing waters.

(2) As river meanders become more pronounced and curved, the two outside banks of one or two meanders may eventually erode toward each other. As the banks between the meanders continue to erode, the neck of land between them becomes narrower.

(3) Eventually the neck of the meander is eroded completely and the river cuts a new, straighter path.

(4) Lastly, deposition builds up between the river channel and the former meander and eventually completely cuts off the meander from the river channel, forming an oxbow lake.

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