Confluence of theBhagirathi andAlaknanda Rivers at theGanges inDevprayag, IndiaThe same confluence viewed from upstream at a different time; note the swirl of sediment from the Alaknanda River
Ingeography, aconfluence (alsoconflux) occurs where two or morewatercourses join to form a singlechannel.[1] A confluence can occur in several configurations: at the point where atributary joins a largerriver (main stem); or where two streams meet to become thesource of a river of a new name (such as the confluence of theMonongahela andAllegheny rivers, forming theOhio River); or where two separated channels of a river (forming ariver island) rejoin downstream from their point of separation.
Confluence of theMississippi,Missouri, andIllinois rivers with normal water levels in 1991, and during a flood in 1993
Confluences are studied in a variety of sciences.Hydrology studies the characteristic flow patterns of confluences and how they give rise to patterns of erosion, bars, and scour pools.[2] The water flows and their consequences are often studied withmathematical models.[3] Confluences are relevant to the distribution of living organisms (i.e.,ecology) as well; "the general pattern [downstream of confluences] of increasing stream flow and decreasing slopes drives a corresponding shift in habitat characteristics."[4]
Another science relevant to the study of confluences ischemistry, because sometimes the mixing of the waters of two streams triggers a chemical reaction, particularly in a polluted stream. TheUnited States Geological Survey gives an example: "chemical changes occur when a stream contaminated withacid mine drainage combines with a stream with near-neutralpH water; these reactions happen very rapidly and influence the subsequent transport of metals downstream of the mixing zone."[5]
A natural phenomenon at confluences that is obvious even to casual observers is a difference in color between the two streams; see images in this article for several examples. According to Lynch, "the color of each river is determined by many things: type and amount of vegetation in the watershed, geological properties, dissolved chemicals,sediments and biologic content – usuallyalgae." Lynch also notes that color differences can persist for miles downstream before they finally blend completely.[6]
Hydrodynamic features of a river/flume confluence can be separated into six identifiable distinct zones, also called confluence flow zones.
Hydrodynamic behaviour of flow in a confluence can be divided into six distinct features[7] which are commonly called confluence flow zones (CFZ). These include
Engineers must design these systems with consideration of factors that ensure the discharge point is structurally stable as the entrance of the lateral culvert into the main structure may compromise the stability of the structure due to the lack of support at the discharge; this often constitutes additional supports in the form of structural bracing.[8][9] The velocities and hydraulic efficiencies should be meticulously calculated and can be altered by integrating different combinations of geometries, components such a gradients, cascades and an adequate junction angle which is sympathetic to the direction of the watercourse's flow to minimise turbulent flow, maximise evacuation velocity and to ultimately maximise hydraulic efficiency.[10]
Since rivers often serve as political boundaries, confluences sometimes demarcate three abutting polities, such as nations, states, or provinces, forming atripoint. Various examples are listed below.
Many major cities, such asChongqing,St. Louis, andKhartoum, arose at confluences; further examples appear in the list. Within a city, a confluence often forms a visually prominent point, so that confluences are sometimes chosen as the site of prominent public buildings or monuments, as inKoblenz,Lyon, andWinnipeg. Cities also often build parks at confluences, sometimes as projects of municipal improvement, as atPortland andPittsburgh. In other cases, a confluence is an industrial site, as inPhiladelphia orMannheim. Often a confluence lies in the sharedfloodplain of the two rivers and nothing is built on it, for example atManaus, described below.
One other way that confluences may be exploited by humans is as sacred places inreligions. Rogers suggests that for the ancient peoples of theIron Age in northwest Europe, watery locations were often sacred, especially sources and confluences.[11] Pre-ChristianSlavic peoples chose confluences as the sites for fortified triangular temples, where they practiced human sacrifice and other sacred rites.[12] InHinduism, the confluence of two sacred rivers often is a pilgrimage site for ritual bathing.[13] In Pittsburgh, a number of adherents toMayanism consider their city's confluence to be sacred.[14]
AtKazungula inZambia, theChobe River flows into theZambezi. The confluence defines thetripoint ofZambia (north of the rivers),Botswana (south of the rivers) andNamibia (west of the rivers). The land border between Botswana andZimbabwe to the east also reaches the Zambezi at this confluence, so there is a second tripoint (Zambia-Botswana-Zimbabwe) only 150 meters downstream from the first. SeeKazungula andQuadripoint, and Gallery below for image.
NearAllahabad, India, theYamuna flows into the Ganges. InHinduism, this is a pilgrimage site for ritual bathing;[16] during aKumbh Mela event tens of millions of people visit the site. In Hindu belief the site is held to be atriple confluence (Triveni Sangam), the third river being the metaphysical (not physically present)Sarasvati.[17]
Karad, inMaharashtra,India, is the site of thePritisangam (meaning: Lovely Confluence), a T-shaped confluence ofKrishna River andKoyna River, where Koyna River mergers into Krishna River forming a T-shape and then the merged rivers flow to the east as Krishna River.[18]
The Kolam Biru in Kuala Lumpur
Kuala Lumpur, the capital ofMalaysia, is where theGombak River (previously known as Sungai Lumpur, which means "muddy river") flows into theKlang River at the site of theJamek Mosque. Recently, the Kolam Biru (Blue Pool), a pool with elaborate fountains, has been installed at the apex of the confluence.[19]
TheJialing flows into theYangtze atChongqing inChina. The confluence forms a focal point in the city, marked by Chaotianmen Square, built in 1998.
In the Far East, theAmur forms the international boundary between China andRussia. TheUssuri, which also demarcates the border, flows into the Amur at a point midway betweenFuyuan in China andKhabarovsk in Russia. The apex of the confluence is located in a rural area, part of China, where a commemorative park, Dongji Square, has been built; it features an enormous sculpture representing the Chinese character for "East".[20] The Amur-Ussuri border region was the location of theSino-Soviet border conflict of 1969; the borderline near the confluence was settled peacefully by treaty in 2008.
InGeorgia, in the town ofPasanauri on the southern slopes of theCaucasus Mountains, the Tetri Aragvi ("White Aragvi") is joined by the Shavi Aragvi ("Black Aragvi"). Together, these two rivers continue as theAragvi River. The conflux is known for its dramatic visual contrast of the two rivers.
TheSeine divides in the historical center ofParis, flowing around two river islands, theÎle Saint-Louis and theÎle de la Cité. At the downstream confluence, where the river becomes a single channel again, the Île de la Cité is crossed by the famousPont Neuf, adjacent to an equestrian statue of KingHenri IV and the historically more recent Vert Galant park. The site has repeatedly been portrayed by artists includingMonet,Renoir, andPissarro.
Further upstream, theMarne empties into the Seine atCharenton-le-Pont andAlfortville, just southeast of the Paris city limits. The site is dominated by theHuatian Chinagora [fr], a four-star hotel under Chinese management.
TheMosel flows into the Rhine further north atKoblenz. The name "Koblenz" itself has its origin in the Latin name "Confluentes". In German, this confluence is known as the "Deutsches Eck" ("German corner") and is the site of an imposing monument to German unification featuring an equestrian statue ofKaiser Wilhelm I.
Upstream inSwitzerland, a small town also namedKoblenz (for the same reason) is where theAare joins the Rhine.
The triple confluence inPassau; from left to right, theInn, theDanube, and theIlz.
Passau, Germany, sometimes called theDreiflüssestadt (City of Three Rivers), is the site of a triple confluence, described thus in a guidebook: "from the north the littleIlz sluices brackish water down from thepeat-richBavarian Forest, meeting the cloudy brown of theDanube as it flows from the west and the pale snow-melt jade of theInn from the south [i.e., theAlps] to create a murky tricolour."[21]
TheLusatian Neisse flows into theOder at a rural location in Poland opposite the German village of Ratzdorf. The two rivers form theOder-Neisse line, the postwar boundary of Germany and Poland.
The GreaterTwin Cities area ofMinneapolis andSt. Paul,Minnesota features two important Mississippi confluences. Near historicalFort Snelling and the town ofMendota—about 9 miles downstream on the Mississippi from Minneapolis—theMinnesota River flows into the Mississippi atPike Island. The area around this confluence is a location of spiritual, cultural, and historical significance to theDakota people and is also the site of the earliest European settlements in the Twin Cities area. About 30 miles further downstream from the Minnesota-Mississippi confluence—and 25 miles downstream from St. Paul—the Mississippi joins with theSt. Croix River nearHastings, Minnesota, andPrescott, Wisconsin.
The Ohio River is formed by the confluence of theMonongahela andAllegheny rivers, located inPittsburgh,Pennsylvania. The site is of great historical significance; in the 1970s it was upgraded by the creation ofPoint State Park, highlighted by a large fountain.
AtCohoes, New York, a few miles north ofAlbany, theMohawk River flows into theHudson in three channels separated by islands. The confluence is historically important: upstream traffic on or along the Hudson often took a left turn at the Mohawk, which offers a uniquely level passageway through theAppalachian Mountains that assisted commerce and the settlement of the West.
AtOttawa, the capital of Canada, theRideau River flows—unusually, as a waterfall—into theOttawa River; seeRideau Falls. On the island separating the two portions of the falls is a park with military monuments, among them theOttawa Memorial.
TheSnake River flows into theColumbia River at Sacagawea State park near theTri-Cities ofWashington. It should also be noted that the significant Yakima river also flows into the Columbia just a few miles upstream, thus giving the region the unofficial preposition of Three Rivers
A section of the Industrial Canal inNew Orleans also serves as the channel for the Gulf Intracoastal Waterway and the Mississippi River-Gulf Outlet Canal. The waterways are said to be 'confluent'.
The term confluence can also apply to the process of merging or flowing together of other substance.[27] For example, it may refer to the merger of the flow of twoglaciers.[28]
^A widely cited work is James L. Best (1986) The morphology of river channel confluences.Progress in Physical Geography 10:157–174. For work citing Best, see[1].
^A recent contribution with review of earlier work is Laurent Schindfessel, Stéphan Creëlle and Tom De Mulder (2015) "Flow patterns in an open channel confluence with increasingly dominant tributary inflow,"Water 7: 4724–4751; available on line.
^Quoted from Beechie et al. (2012), who cite earlier work. Tim Beechie, John S. Richardson,Angela M. Gurnell, and Junjiro Negishi (2012) "Watershed processes, human impacts, and process-based restoration." In Philip Roni and Tim Beechie (eds.) (2012)Stream and Watershed Restoration: A Guide to Restoring Riverine Processes and Habitats, John Wiley & Sons. Excerpts available on line at Google Books.
^U.S. Geological Survey, "How do contaminants mix at the confluence of two streams?", on line at[2]Archived 2021-03-28 at theWayback Machine.
^David Lynch (2014) "The Confluence of Rivers"; Earth Science Picture of the Day, at[3].
^Best, James L. (1987). "Flow Dynamics at River Channel Confluences: Implications for Sediment Transport and Bed Morphology".Recent Developments in Fluvial Sedimentology. pp. 27–35.doi:10.2110/pec.87.39.0027.ISBN978-0-918985-67-5.
^Moore, I.D.; García, D. Becerril; Sezen, H.; Sheldon, T. (2012-07-20).Structural Design of Culvert Joints. National Cooperative Highway Research Program, Transportation Research Board, National Academies of Sciences, Engineering, and Medicine. Washington, D.C.: Transportation Research Board.ISBN978-0-309-43495-9.
^Rogers, Adam (2011)Late Roman Towns in Britain: Rethinking Change and Decline. Cambridge: Cambridge University Press, p. 42. Excerpts available on line at Google Books.
^Gasparini, Evel (n.d.) "Slavic religion", inEncyclopedia Britannica, on line edition:[4]
^Source: Letizia (2017), who writes, "as rivers are considered holy entities, at the meeting of two streams the 'sacredness' of the first river add to that of the second one. The confluence seems to have a sort of 'additive fame' ... because it gives pilgrims the chance to bathe in two rivers at the same time."
^Ann Rodgers, "So how did the Point get on a Mayan calendar?",Pittsburgh Post-Gazette, June 22, 2008. On line at[5].
^SeeNew Straits Times, August 28, 2017, 'Najib launches River of Life, Blue Pool projects", at[8].
^See Bruno Maçães, "Signs and Symbols on the Sino-Russian Border", published inThe Diplomat. On line at[9].
^See Andrea Schulte-Peevers, Kerry Christiani, Marc Di Duca, Catherine Le Nevez, Tom Masters, Ryan Ver Berkmoes, and Benedict Walker (2016)Lonely Planet Germany, Lonely Planet Publishing. Excerpts posted on line at Google Books:[10]
^Kogovšek, Janja; Petrič, Metka; Zupan Hajna, Nadja; Pipan, Tanja."Planinska jama" [Planina Cave]. In Šmid Hribar, Mateja; Golež, Gregor; Podjed, Dan; Kladnik, Drago; Erhartič, Bojan; Pavlin, Primož; Ines, Jerele (eds.).Enciklopedija naravne in kulturne dediščine na Slovenskem [Encyclopedia of Natural and Cultural Heritage in Slovenia] (in Slovenian). Archived fromthe original on 19 April 2012. Retrieved17 May 2012.
^Park, Chris C. (2017).A dictionary of environment and conservation. Michael Allaby (3 ed.). [Oxford].ISBN978-0-19-182632-0.OCLC970401188.{{cite book}}: CS1 maint: location missing publisher (link)
^Vladimir Kotlyakov and Anna Komarova (2006)Elsevier's Dictionary of Geography: in English, Russian, French, Spanish and German. Elsevier. Passage cited may be accessed onGoogle Books.
Letizia, Chiara (2017) "The Sacred Confluence, between Nature and Culture," in Marie Lecomte-Tilouine (ed.)Nature, Culture and Religion at the Crossroads of Asia. Routledge. Extracts available on line at Google Books.
