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The Amazon River (dark blue) and the rivers which flow into it (medium blue)
The Loboc River in Bohol, Philippines



Rivers and streams are often considered major features within a landscape, however, they actually only cover around 0.1% of the land on Earth. They are made more obvious and significant to humans by the fact that many human cities and civilizations are built around the freshwater supplied by rivers and streams.[3] Most of the major cities of the world are situated on the banks of rivers, as they are, or were, used as a source of water, for obtaining food, for transport, as borders, as a defensive measure, as a source of hydropower to drive machinery, for bathing, and as a means of disposing of waste.



The Colorado River at Horseshoe Bend, Arizona
The Porvoo River (Porvoonjoki) in the medieval town of Porvoo, Finland

A river begins at a source (or more often several sources), follows a path called a course, and ends at a mouth or mouths. The water in a river is usually confined to a channel, made up of a stream bed between banks. In larger rivers there is often also a wider floodplain shaped by flood-waters over-topping the channel. Floodplains may be very wide in relation to the size of the river channel. This distinction between river channel and floodplain can be blurred, especially in urban areas where the floodplain of a river channel can become greatly developed by housing and industry.









Subsurface streams


Permanence of flow

An intermittent river (or ephemeral river) only flows occasionally and can be dry for several years at a time. These rivers are found in regions with limited or highly variable rainfall, or can occur because of geologic conditions such as a highly permeable river bed. Some ephemeral rivers flow during the summer months but not in the winter. Such rivers are typically fed from chalk aquifers which recharge from winter rainfall. In England these rivers are called bournes and give their name to places such as Bournemouth and Eastbourne. Even in humid regions, the location where flow begins in the smallest tributary streams generally moves upstream in response to precipitation and downstream in its absence or when active summer vegetation diverts water for evapotranspiration. Normally-dry rivers in arid zones are often identified as arroyos or other regional names.





Topographical classification


Alluvial rivers can be further classified by their channel pattern as meandering, braided, wandering, anastomose, or straight. The morphology of an alluvial river reach is controlled by a combination of sediment supply, substrate composition, discharge, vegetation, and bed aggradation.

At the start of the 20th century William Morris Davis devised the "cycle of erosion" method of classifying rivers based on their "age". Although Davis's system is still found in many books today, after the 1950s and 1960s it became increasingly criticized and rejected by geomorphologists. His scheme did not produce testable hypotheses and was therefore deemed non-scientific.[8] Examples of Davis's river "ages" include:

  • Mature river: A river with a gradient that is less steep than those of youthful rivers and flows more slowly. A mature river is fed by many tributaries and has more discharge than a youthful river. Its channels erode wider rather than deeper. Examples are the Mississippi, Saint Lawrence, Danube, Ohio, Thames and Paraná rivers.


Biotic classification


  • The crenon is the uppermost zone at the source of the river. It is further divided into the eucrenon (spring or boil zone) and the hypocrenon (brook or headstream zone). These areas have low temperatures, reduced oxygen content and slow moving water.

Whitewater classification


Stream order classification






Rivers have been a source of food since pre-history.[14] They are often a rich source of fish and other edible aquatic life, and are a major source of fresh water, which can be used for drinking and irrigation. Rivers help to determine the urban form of cities and neighbourhoods and their corridors often present opportunities for urban renewal through the development of foreshoreways such as river walks. Rivers also provide an easy means of disposing of waste water and, in much of the less developed world, other wastes.

Rivers have been used for navigation for thousands of years. The earliest evidence of navigation is found in the Indus Valley Civilization, which existed in northwestern India around 3300 BC.[15] Riverine navigation provides a cheap means of transport, and is still used extensively on most major rivers of the world like the Amazon, the Ganges, the Nile, the Mississippi, and the Indus. Since river boats are often not regulated, they contribute a large amount to global greenhouse gas emissions, and to local cancer due to inhaling of particulates emitted by the transports.[16][17]

Rivers have been important in determining political boundaries and defending countries. For example, the Danube was a long-standing border of the Roman Empire, and today it forms most of the border between Bulgaria and Romania. The Mississippi in North America and the Rhine in Europe are major east-west boundaries in those continents. The Orange and Limpopo Rivers in southern Africa form the boundaries between provinces and countries along their routes.


Watermill in Belgium


The coarse sediments, gravel, and sand, generated and moved by rivers are extensively used in construction. In parts of the world this can generate extensive new lake habitats as gravel pits re-fill with water. In other circumstances it can destabilise the river bed and the course of the river and cause severe damage to spawning fish populations which rely on stable gravel formations for egg laying. In upland rivers, rapids with whitewater or even waterfalls occur. Rapids are often used for recreation, such as whitewater kayaking.[19]


The organisms in the riparian zone respond to changes in river channel location and patterns of flow. The ecosystem of rivers is generally described by the river continuum concept, which has some additions and refinements to allow for dams and waterfalls and temporary extensive flooding. The concept describes the river as a system in which the physical parameters, the availability of food particles and the composition of the ecosystem are continuously changing along its length. The food (energy) that remains from the upstream part is used downstream.

The general pattern is that the first order streams contain particulate matter (decaying leaves from the surrounding forests) which is processed there by shredders like Plecoptera larvae. The products of these shredders are used by collectors, such as Hydropsychidae, and further downstream algae that create the primary production become the main food source of the organisms. All changes are gradual and the distribution of each species can be described as a normal curve, with the highest density where the conditions are optimal. In rivers succession is virtually absent and the composition of the ecosystem stays fixed .


The chemistry of rivers is complex and depends on inputs from the atmosphere, the geology through which it travels and the inputs from man's activities. The chemical composition of the water has a large impact on the ecology of that water for both plants and animals and it also affects the uses that may be made of the river water. Understanding and characterising river water chemistry requires a well designed and managed sampling and analysis.

Brackish water

Brackish waster occurs in most rivers where they meet the sea. The extent of brackish water may extend a significant distance upstream, especially in areas with high tidal ranges.


The mouth of the River Seaton in Cornwall after heavy rain caused flooding and significant erosion of the beach

Flooding is a natural part of a river's cycle. The majority of the erosion of river channels and the erosion and deposition on the associated floodplains occur during the flood stage. In many developed areas, human activity has changed the form of river channels, altering magnitudes and frequencies of flooding. Some examples of this are the building of levees, the straightening of channels, and the draining of natural wetlands. In many cases human activities in rivers and floodplains have dramatically increased the risk of flooding. Straightening rivers allows water to flow more rapidly downstream, increasing the risk of flooding places further downstream. Building on flood plains removes flood storage, which again exacerbates downstream flooding. The building of levees only protects the area behind the levees and not those further downstream. Levees and flood-banks can also increase flooding upstream because of the back-water pressure as the river flow is impeded by the narrow channel banks. Detention basins finally also reduce the risk of flooding significantly by being able to take up some of the flood water.


Studying the flows of rivers is one aspect of hydrology.[20]


River meandering course

Rivers flow downhill with their power derived from gravity. The direction can involve all directions of the compass and can be a complex meandering path.[21][22][23]

Rivers flowing downhill, from river source to river mouth, do not necessarily take the shortest path. For alluvial streams, straight and braided rivers have very low sinuosity and flow directly down hill, while meandering rivers flow from side to side across a valley. Bedrock rivers typically flow in either a fractal pattern, or a pattern that is determined by weaknesses in the bedrock, such as faults, fractures, or more erodible layers.




Fluvial erosion

In its youthful stage the river causes erosion in the water-course, deepening the valley. Hydraulic action loosens and dislodges the rock which further erodes the banks and the river bed. Over time, this deepens the river bed and creates steeper sides which are then weathered.


Waterfalls also form in the youthful river valley where a band of hard rock overlays a layer of soft rock. Differential erosion occurs as the river erodes the soft rock more readily than the hard rock, this leaves the hard rock more elevated and stands out from the river below. A plunge pool forms at the bottom and deepens as a result of hydraulic action and abrasion.[24]

Sediment yield


Frozen river in Alaska


River bank repair

Rivers are often managed or controlled to make them more useful or less disruptive to human activity.




See also

Arts, entertainment, and media


  1. 1 2 "Mapping, Remote Sensing, and Geospatial Data: What is the difference between 'mountain', 'hill', and 'peak'; 'lake' and 'pond'; or 'river' and 'creek?'". United States Geological Survey. Retrieved 25 August 2019.
  2. "WordNet Search: River". The Trustees of Princeton University. Retrieved 2 October 2009.
  3. Basic Biology (16 January 2016). "River".
  5. Garde, R.J. (1995). History of fluvial hydraulics. New Age Publishers. p. 14. ISBN 978-81-224-0815-7. OCLC 34628134.
  6. Garde, R.J. (1995). History of fluvial hydraulics. New Age Publishers. p. 19. ISBN 978-81-224-0815-7. OCLC 34628134.
  7. "Sand River" in Iraq is actually a rapid movement of ice blocks. Tampabayreview.com. Retrieved on 14 July 2016.
  9. River Classification scheme. sepa.org.uk
  10. NZ’s River Environment Classification system (REC). maf.govt.nz
  12. Illies, J.; Botosaneanu, L. (1963). "Problémes et méthodes de la classification et de la zonation éologique des eaux courantes, considerées surtout du point de vue faunistique". Mitt. Int. Ver. Theor. Angew. Limnol. 12: 1–57.
  14. "National Museum of Prehistory-The Peinan Site-Settlements of the Prehistoric Times". nmp.gov.tw.
  15. "WWF – The World's Rivers". panda.org.
  16. Meybeck, Michel (1993). "Riverine transport of atmospheric carbon: Sources, global typology and budget". Water, Air, & Soil Pollution. 70 (1–4): 443–463. Bibcode:1993WASP...70..443M. doi:10.1007/BF01105015. S2CID 189854355.
  17. Albrecht, Achim (2003). "Validating riverine transport and speciation models using nuclear reactor-derived radiocobalt". Journal of Environmental Radioactivity. 66 (3): 295–307. doi:10.1016/S0265-931X(02)00133-9. PMID 12600761.
  18. "Logging Camps: The Early Years". Minnesota DNR.
  19. Draper, Nick; Hodgson, Christopher (2008). Adventure Sport Physiology. John Wiley & Sons. ISBN 978-0-470-31913-0.
  21. Rosenberg, Matt (8 June 2006). "Do All Rivers Flow South?". About.com.
  22. Rosenberg, Matt. "Rivers Flowing North: Rivers Only Flow Downhill; Rivers Do Not Prefer to Flow South". About.com.
  24. "Landforms of the upper valley". www.coolgeography.co.uk. Retrieved 2 December 2016.

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