Distributary

"Branch river" redirects here. For other uses, seeBranch River (disambiguation).

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

Adistributary,or adistributary channelis astreamchannelthat branches off and flowsaway froma main stream channel. It is the opposite of atributary,a stream that flowstowards and intoanother stream or river. Distributaries are a result ofriver bifurcationand are often found where a river approaches alakeor anoceanand divides into distributary networks; as such they are a common feature ofriver deltas.They can also occur inland, onalluvial fans,or where a tributary stream bifurcates as it nears itsconfluencewith 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.

Related terms

Common terms to name individual river distributaries inEnglish-speaking countriesarearmandchannel.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 theFraser River,or the West Channel of theMackenzie River), or to one that does (e.g. Annacis Channel and Annieville Channel of theFraser River,separated byAnnacis Island).

In Australia, the termanabranchis used to refer to a distributary that diverts from the main course of the river and rejoins it later. InNorth Americasuch a branching river is called abraided river.

North America

Atchafalaya River

InLouisiana,theAtchafalaya Riveris an important distributary of theMississippi River.Because the Atchafalaya takes a steeper route to theGulf of Mexicothan does the Mississippi, over several decades the Atchafalaya has captured more and more of the Mississippi's flow, after the Mississippi meandered into theRed River of the South.TheOld River Control Structure,adamwhich regulates the outflow from the Mississippi into the Atchafalaya, was completed by theArmy Corps of Engineersin 1963. The dam is intended to prevent the Atchafalaya from capturing the main flow of the Mississippi and stranding the ports ofBaton RougeandNew Orleans.

InBritish Columbia,Canada, theFraser Riverhas numerous sloughs and side-channels which may be defined as distributaries. This river's final stretch has three main distributaries: theNorth Armand theSouth Arm,and a few smaller ones adjoining them.

Examples of inland distributaries:

• Teton River—a tributary ofHenrys ForkinIdaho—splits into two distributary channels, the North Fork and South Fork, which join Henrys Fork miles apart.
• Parting of the WatersNational Landmark within Wyoming'sTeton Wildernesson theContinental DividewhereNorth Two Ocean Creeksplits into two distributaries, Pacific Creek and Atlantic Creek, which ultimately flow into their respective oceans.
• Kings River (California)has deposited a large alluvial fan at the transition from its canyon in theSierra Nevadamountains to the flatCentral Valley.Distributaries flow north into the Pacific Ocean via theSan Joaquin Riverand south into anendorheic basinsurroundingTulare Lake.
• TheQu'Appelle River,inSaskatchewanandManitoba,is a distributary of theSouth Saskatchewan River.Its flow is controlled by theQu'Appelle River Dam.This dam forms the southern arm ofLake Diefenbaker.

South America

TheCasiquiare canalis an inland distributary of the upperOrinoco,which flows southward into theRio Negro,forming a unique naturalcanalbetween the Orinoco andAmazon riversystems. It is the largest river on the planet that links two major river systems.

Europe

Satellite image of part of theRhine–Meuse–Scheldt delta

• TheIJssel,theWaaland theNederrijn(Lower Rhine) are the three principal distributaries of theRhine.These are formed by two separate bifurcations within theRhine–Meuse–Scheldt delta.
• TheAkhtuba Riveris a major distributary of theVolga.The bifurcation occurs close to, but before, theVolga Delta.
• TheTärendö Riverin northernSwedenis aninland distributary,far from the mouth of the river. It begins at theTorne Riverand ends at theKalix River.
• TheLittle DanubeinSlovakiabranches off from theDanubenear Bratislava, and flows into theVahbefore rejoining the main river nearKomárno.The area in the middle is the largest freshwater island in Europe.
• TheAbbey River,Limerick,inIrelandis a distributary arm of theRiver Shannon.It rejoins the Shannon to form an island upon whichKing John's Castleis built.

Asia

Eastern Asia

TheHuai Riverin China splits into three streams. The main stream passes through the Sanhe Sluice, goes out of the Sanhe river, and enters theYangtze RiverthroughBaoyingLake andGaoyou Lake.On the east bank ofHongze Lake,another stream goes out ofGaoliang gianGate and enters theYellow Seaat theportof Bidan through Subei Guan'gai Zongqu, the mainirrigationchannel of NorthernJiangsu); 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 ofLianyungangcity, and flows into Haizhou Bay through the Hongkou.

Southeast Asia

TheTha Chin RiverandNoi Riverare distributaries of theChao Phraya RiverinThailand,splitting off from the latter about 200 kilometers upstream from theBay of Bangkok.

TheBrantas RiverinEast Java,Indonesia,branches off into two distributaries,Mas River,also known as Surabaya River, andPorong River.

Indian Subcontinent

A seasonal distributary of theKaveri Riveron the Kaveri delta, nearNannilam,India

• Kollidam Riveris a distributary of theKaveri River.
• Himalayanrivers including Ganges, Brahmaputra andIndusplus many tributaries form inland distributaries over vastalluvial fansas they transition from the mountain region to the flatIndo-Gangetic Plain.These areas are highly flood-prone, for example the2008 Bihar floodon theKosi River.
• Padma Riveris the main distributary of theGangesinBangladesh.
• Hoogli Riveris aGangesdistributary that flows throughIndia,whereas most of the Ganges-Brahmaputracomplex enters the sea throughBangladesh.
• Nara Riveris a distributary of theIndus River.

Africa

• TheNile Riverhas two distributaries, theRosettaand theDamiettabranches. According toPliny the Elderit had in ancient times seven distributaries (east to west):
  • The Pelusiac
  • The Tanitic
  • The Mendesian
  • The Phatnitic
  • The Sebennytic
  • The Bolbitine
  • The Canopic

SeeHistory of the Nile Delta.

• TheOkavango Riverends in many distributaries in a large inland delta called theOkavango Delta.It is an example of distributaries that do not flow into any other body of water.

Oceania

Delta of Papua New Guinea'sFly River

Australia

A number of the rivers that flow inland from Australia'sGreat Dividing Rangeform 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 theWimmera Riverinto Lake Coorong, and Tyrrell Creek, which flows from theAvoca RiverintoLake Tyrrell,are two distributaries inVictoria.TheNarran Riverflows from theBalonne RiverinQueenslandintoNarran LakeinNew South Wales.

Papua New Guinea

Many of Papua New Guinea's major rivers flow into theGulf of Papuathrough marshy, low-lying country, allowing for wide, many-branched deltas. These include theFly River,which splits into three major and several minor rivers close to its mouth. TheBamu Riversplits into several channels close to its mouth, among them theBebea,Bina,Dibiri,andAramia.TheKikori Riveralso splits into a multitude of channels as it crosses the plains close to the Gulf of Papua. ThePurari Riversplits into three major channels as it approaches its mouth.

New Zealand

New Zealand's second-longest river, theClutha River,splits into two arms, theMatauand theKoua,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 theCanterbury Plainsin the central South Island arebraided rivers,and several of these split into separate branches before reaching the coast. Notable among these is theRangitata River,the two arms of which are separated by the low-lyingRangitata Island.

References

Citations

• Olariu, Cornel; Bhattacharya, Janok P. (2006)."Terminal Distributary Channels and Delta Front Architecture of River-Dominated Delta Systems"(PDF).Journal of Sedimentary Research.76(2). Society for Sedimentary Geology: 212–233.Bibcode:2006JSedR..76..212O.doi:10.2110/jsr.2006.026.Archived fromthe original(PDF)on December 23, 2015.RetrievedDecember 10,2013.