Junction of the Yukon and Koyukuk Rivers, Alaska

An anabranch is a section of a

river A river is a natural flowing watercourse, usually freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the ...

or stream that diverts from the main channel or

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushr ...

of the

watercourse A stream is a continuous body of surface water flowing within the bed and banks of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long large streams ...

and rejoins the main stem downstream. Local anabranches can be the result of small islands in the watercourse. In larger anabranches, the flow can diverge for a distance of several kilometers before rejoining the main channel.

Word usage and related terms

The term ''anabranch'', in its

hydrological Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...

meaning, is used more frequently in Australia than in the rest of the English-speaking world. The term ''anabranching river'' describes a

with many anabranches, whilst an anastomosing river is an organic-rich subset of this

type. The term

braided river A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, '' aits'' or ''eyots''. Braided streams tend to occur in rivers with high sedime ...

describes

s which are divided by small

islands An island or isle is a piece of subcontinental land completely surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be cal ...

into multiple channel threads within a single main channel, but the term does not describe the multiple channels of an anabranching river. A

distributary A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel. Distributaries are a common feature of river deltas. The phenomenon is known as river bifurcation. The opposite of a distribut ...

is a branch of a

that does not rejoin the main channel; these are common on and near

river delta A river delta is a landform shaped like a triangle, created by deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more ra ...

s. A

bayou In usage in the Southern United States, a bayou () is a body of water typically found in a flat, low-lying area. It may refer to an extremely slow-moving stream, river (often with a poorly defined shoreline), marshy lake, wetland, or creek. The ...

is often an anabranch. An anabranch that gets cut off from the main channel becomes an

oxbow lake An oxbow lake is a U-shaped lake or pool that forms when a wide meander of a river is cut off, creating a free-standing body of water. In South Texas, oxbows left by the Rio Grande are called '' resacas''. In Australia, oxbow lakes are cal ...

, known in Australia as a

billabong Billabong ( ) is an Australian term for an oxbow lake, an isolated pond left behind after a river changes course. Billabongs are usually formed when the path of a creek or river changes, leaving the former branch with a dead end. As a result ...

Examples

* The

Magdalena River The Magdalena River ( es, Río Magdalena, ; less commonly ) is the main river of Colombia, flowing northward about through the western half of the country. It takes its name from the biblical figure Mary Magdalene. It is navigable through much o ...

, in Colombia, bifurcates in El Banco in two branches: Brazo de Loba (Shewolf Branch in Spanish) and Brazo de Mompox. The first one, Brazo de Loba is the main navigable channel and is 177 km long. Brazo de Mompox is thus the anabranch. There are several other branches that join those two main branches, interconnected by swamps ("ciénagas"), the main ones being Quitasol, Chicagua and La Victoria. Between Brazo de Loba and Brazo de Mompox is the island of Mompox or Margarita Island, a sunken geological block of 2.200 square km between the faults of Chicagua and El Romeral. * In the

Fraser River The Fraser River is the longest river within British Columbia, Canada, rising at Fraser Pass near Blackrock Mountain in the Rocky Mountains and flowing for , into the Strait of Georgia just south of the City of Vancouver. The river's annua ...

delta of

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost Provinces and territories of Canada, province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

, North Arm Fraser River, Middle Arm Fraser River, and South Arm Fraser River each fall into Georgia Strait separately. On the other hand,

Annacis Island Annacis Island is a narrow island under the jurisdiction of City of Delta in Lower Mainland, British Columbia, located just downstream of the south arm of the Fraser River bifurcation between Lulu Island to the north and the Delta peninsula t ...

splits (South Arm) Fraser River into the (main)

Annieville Channel North Delta (founded as Annieville) is a largely middle-class commuter town situated in the Lower Mainland, of British Columbia, Canada. The community is the most populous of the three communities (North Delta, Ladner, and Tsawwassen) that make ...

and the (smaller) Annacis Channel, which rejoin below the island. * In western

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

the Great Darling Anabranch is the ancestral path of the

Darling River The Darling River (Paakantyi: ''Baaka'' or ''Barka'') is the third-longest river in Australia, measuring from its source in northern New South Wales to its conflu ence with the Murray River at Wentworth, New South Wales. Including its longes ...

, dividing south of Menindee and extending for 460 km before joining the

Murray River The Murray River (in South Australia: River Murray) ( Ngarrindjeri: ''Millewa'', Yorta Yorta: ''Tongala'') is a river in Southeastern Australia. It is Australia's longest river at extent. Its tributaries include five of the next six longe ...

. The anabranch contains flowing water only in wetter years. * In the Lower Simpson Desert, in

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

Kallakoopah Creek The Kallakoopah Creek, part of the Lake Eyre basin, is a watercourse located in the southern part of the Simpson Desert in the Australian state of South Australia. It is an anabranch of Warburton Creek The Warburton River (or Warburton Cree ...

is an anabranch of the

Warburton River The Warburton River (or Warburton Creek) is a freshwater stream in the far north of South Australia that flows in a south westerly direction and discharges into the eastern side of Lake Eyre. It is one of the state's largest rivers, and is par ...

that flows during major Warburton floods of over 5 m in depth. The Kallakoopah is approximately 400 km long and members of the Lake Eyre Yacht Club and others have used it to sail a circular route to

Lake Eyre Lake Eyre ( ), officially known as Kati Thanda–Lake Eyre, is an endorheic lake in east-central Far North South Australia, some north of Adelaide. The shallow lake is the depocentre of the vast endorheic Lake Eyre basin, and contains ...

by traveling down the Kallakoopah and returning via the Warburton. * The Bahr el Zeraf in southern Sudan splits from the Bahr al Jabal section of the

White Nile The White Nile ( ar, النيل الأبيض ') is a river in Africa, one of the two main tributaries of the Nile, the other being the Blue Nile. The name comes from the clay sediment carried in the water that changes the water to a pale colo ...

and flows for 240 km (150 mi), before rejoining the White Nile proper upriver from

Malakal Malakal is a city in South Sudan. It is the capital of Upper Nile State, South Sudan, along the White Nile River. It also serves as the headquarter of Malakal county and it used to be the headquarter of Upper Nile Region from 1970s to late 1990s ...

. * Approximately 15 km out of

Charters Towers Charters Towers is a rural town in the Charters Towers Region, Queensland, Australia. It is by road south-west from Townsville on the Flinders Highway. During the last quarter of the 19th century, the town boomed as the rich gold deposits unde ...

(

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

/ Australia) is a section of the

Burdekin River The Burdekin River is a river located in North and Far North Queensland, Australia. The river rises on the northern slopes of Boulder Mountain at Valley of Lagoons, part of the western slope of the Seaview Range, and flows into the Coral Sea a ...

known as 'the anabranch'. This strip of water is separate from the main flood way, and is typically dry during the sunnier months. Once there is consistent rain, it will meet up with the river again and flood with fresh water. It is well known for barramundi fishing. * Probably because waterways played an important role in infrastructure, anabranches and the resulting river islands are often found in old cities as with the

Île de la Cité Île de la Cité (; English: City Island) is an island in the river Seine in the center of Paris. In the 4th century, it was the site of the fortress of the Roman governor. In 508, Clovis I, the first King of the Franks, established his palac ...

in Paris.

References

{{Authority control Fluvial landforms Rivers Water streams Geomorphology