An oxbow lake starts out as a curve, or meander, in a river. A lake forms as the river finds a different, shorter, course. The meander becomes an oxbow lake along the side of the river.

Oxbow lakes usually form in flat, low-lying plains close to where the river empties into another body of water. On these plains, rivers often have wide meanders.

Meanders that form oxbow lakes have two sets of curves: one curving away from the straight path of the river and one curving back. The corners of the curves closest to each other are called concave banks. The concave banks erode over time. The force of the rivers flowing water wears away the land on the meanders concave banks.

The banks opposite the concave banks are called convex banks. The opposite of erosion happens here. Silt and sediment build up on convex banks. This build-up is called deposition.

Erosion and deposition eventually cause a new channel to be cut through the small piece of land at the narrow end of the meander. The river makes a shortcut. Oxbow lakes are the remains of the bend in the river.

Oxbow lakes are stillwater lakes. This means that water does not flow into or out of them. There is no stream or spring feeding the lake, and it doesnt have a natural outlet. Oxbow lakes often become swamps or bogs, and they often dry up as their water evaporates.

Oxbow lakes can be rich wildlife habitats. Along the Amazon River in South America, oxbow lakes are common and their still waters provide a unique habitat for plants and wildlife. Giant river otters frequently live in the Amazons oxbow lakes, and feed on about 5 kilograms (11 pounds) of fish per day.

People often create oxbow lakes. The Mississippi River is shorter now than it was in the 19th century, for instance, because engineers have cut off hundreds of meanders. This created hundreds of oxbow lakes. These lakes eventually dried up to create acres of land for farming, housing, and industry.

An oxbow lake gets its name from the U-shaped collar placed around an oxs neck to which a plow is attached. It can also be called a horseshoe lake, a loop lake, or a cutoff lake.

oxbow lake
The swampy remains of an oxbow lake are evident in the jungle surrounding the Ramu River in Papua New Guinea.

Billabong
In Australia, oxbow lakes are called billabongs. A billabong is the setting for the unofficial national anthem of Australia, Waltzing Matilda.

billabong
Noun

Australian name for an oxbow lake.

bog
Noun

wetland of soft ground made mostly of decaying plant matter.

Noun

waterway between two relatively close land masses.

concave bank
Noun

the outside bank of a rounded bend in a river.

convex bank
Noun

inside bank of a rounded bend in a river.

deposition
Noun

process of silt and sediment building up in an area.

engineer
Noun

person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).

erode
Verb

to wear away.

evaporate
Verb

to change from a liquid to a gas or vapor.

farming
Noun

the art, science, and business of cultivating the land for growing crops.

fish
Noun

aquatic animals with gills, and usually fins and scales.

giant river otter
Noun

aquatic otter up to six feet long, native to the Amazon, Orinoco, and La Plata rivers of South America.

Noun

environment where an organism lives throughout the year or for shorter periods of time.

housing
Noun

shelters where people live.

industry
Noun

activity that produces goods and services.

Noun

body of water surrounded by land.

meander
Noun

large curve in a lake or stream.

ox
Noun

large bovine often used for hauling heavy loads.

Noun

lake formed from an abandoned bend in a river.

Noun

flat, smooth area at a low elevation.

plow
noun, verb

tool used for cutting, lifting, and turning the soil in preparation for planting.

Noun

large stream of flowing fresh water.

Noun

solid material transported and deposited by water, ice, and wind.

Noun

small sediment particles.

spring
Noun

small flow of water flowing naturally from an underground water source.

still-water lake
Noun

body of water with no streams or springs flowing into or out of it.

Noun

body of flowing water.

Noun

land permanently saturated with water and sometimes covered with it.