A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel, a phenomenon known as river bifurcation. A distributary is effectively the opposite of a tributary, which is a stream that flows towards and into another stream or river. Distributaries are often found where a stream approaches a lake or an ocean; as such, they are a common feature of river deltas. They can also occur inland, on alluvial fans, or where a tributary stream bifurcates as it nears its confluence with a larger stream. In some cases, a minor distributary can divert so much water from the main channel that it can later become the main route.

Rhine–Meuse–Scheldt delta, with the flow from right to left, showing several streams branching off from their main streams

Related terms edit

Common terms to name individual river distributaries in English-speaking countries are arm and channel. These terms may refer to a distributary that does not rejoin the channel from which it has branched (e.g., the North, Middle, and South Arms of the Fraser River, or the West Channel of the Mackenzie River), or to one that does (e.g. Annacis Channel and Annieville Channel of the Fraser River, separated by Annacis Island).

In Australia, the term anabranch is used to refer to a distributary that diverts from the main course of the river and rejoins it later. In North America an anabranching river is called a braided stream.

North America edit

Atchafalaya River

In Louisiana, the Atchafalaya River is an important distributary of the Mississippi River. Because the Atchafalaya takes a steeper route to the Gulf of Mexico than does the Mississippi, over several decades the Atchafalaya has captured more and more of the Mississippi's flow, after the Mississippi meandered into the Red River of the South. The Old River Control Structure, a dam which regulates the outflow from the Mississippi into the Atchafalaya, was completed by the Army Corps of Engineers in 1963. The dam is intended to prevent the Atchafalaya from capturing the main flow of the Mississippi and stranding the ports of Baton Rouge and New Orleans.[1]

In British Columbia, Canada, the Fraser River has numerous sloughs and side-channels which may be defined as distributaries. This river's final stretch has three main distributaries: the North Arm and the South Arm, and a few smaller ones adjoining them.

Examples of inland distributaries:

South America edit

The Casiquiare canal is an inland distributary of the upper Orinoco, which flows southward into the Rio Negro, forming a unique natural canal between the Orinoco and Amazon river systems. It is the largest river on the planet that links two major river systems.

Europe edit

Satellite image of part of the Rhine–Meuse–Scheldt delta

Asia edit

Eastern Asia edit

The Huai River in China splits into three streams. The main stream passes through the Sanhe Sluice, goes out of the Sanhe river, and enters the Yangtze River through Baoying Lake and Gaoyou Lake. On the east bank of Hongze Lake, another stream goes out of Gaoliangjian Gate and enters the Yellow Sea at the port of Bidan through Subei Guan'gai Zongqu, the main irrigation channel of Northern Jiangsu); its total length is 168 kilometers. The third stream leaves the Erhe lock on the northeast bank of Hongze Lake, passes the Huaishuhe River to the north of Lianyungang city, and flows into Haizhou Bay through the Hongkou.

Southeast Asia edit

The Tha Chin River and Noi River are distributaries of the Chao Phraya River in Thailand, splitting off from the latter about 200 kilometers upstream from the Bay of Bangkok.

The Brantas River in East Java, Indonesia, branches off into two distributaries, Mas River, also known as Surabaya River, and Porong River.[2]

Indian Subcontinent edit

A seasonal distributary of the Kaveri River on the Kaveri delta, near Nannilam, India

Africa edit

  • The Nile River has two distributaries, the Rosetta and the Damietta branches. According to Pliny the Elder it had in ancient times seven distributaries (east to west):
    • The Pelusiac
    • The Tanitic
    • The Mendesian
    • The Phatnitic
    • The Sebennytic
    • The Bolbitine
    • The Canopic
See History of the Nile Delta.
  • The Okavango River ends in many distributaries in a large inland delta called the Okavango Delta. It is an example of distributaries that do not flow into any other body of water.

Oceania edit

Delta of Papua New Guinea's Fly River

Australia edit

A number of the rivers that flow inland from Australia's Great Dividing Range form distributaries, most of which flow only intermittently during times of high river levels and end in shallow lakes or simply peter out in the deserts. Yarriambiack Creek, which flows from the Wimmera River into Lake Coorong, and Tyrrell Creek, which flows from the Avoca River into Lake Tyrrell, are two distributaries in Victoria. The Narran River flows from the Balonne River in Queensland into Narran Lake in New South Wales.

Papua New Guinea edit

Many of Papua New Guinea's major rivers flow into the Gulf of Papua through marshy, low-lying country, allowing for wide, many-branched deltas. These include the Fly River, which splits into three major and several minor rivers close to its mouth. The Bamu River splits into several channels close to its mouth, among them the Bebea, Bina, Dibiri, and Aramia. The Kikori River also splits into a multitude of channels as it crosses the plains close to the Gulf of Papua. The Purari River splits into three major channels as it approaches its mouth.

New Zealand edit

New Zealand's second-longest river, the Clutha River, splits into two arms, the Matau and the Koua, some 10 kilometres from the South Island's Pacific Coast. A large island, Inch Clutha, lies between the two arms. Many of the rivers crossing the Canterbury Plains in the central South Island are braided rivers, and several of these split into separate branches before reaching the coast. Notable among these is the Rangitata River, the two arms of which are separated by the low-lying Rangitata Island.

References edit

  1. ^ John McPhee, The Control of Nature
  2. ^ Valiant, Raymond (2014). TANTANGAN DALAM PENGELOLAAN SUMBERDAYA AIR UNTUK MENCAPAI LINGKUNGAN LESTARI BERKELANJUTAN: POTRET DAERAH ALIRAN SUNGAI (DAS) BRANTAS. Seminar Pekan DAS Brantas 2014. Fakultas Teknik Universitas Brawijaya Malang. Retrieved 28 March 2024.

Citations edit