Rivers Classification Essay


Coastal (Surge Flood)

A coastal flood, as the name suggests, occurs in areas that lie on the coast of a sea, ocean, or other large body of open water. It is typically the result of extreme tidal conditions caused by severe weather. Storm surge — produced when high winds from hurricanes and other storms push water onshore — is the leading cause of coastal flooding and often the greatest threat associated with a tropical storm. In this type of flood, water overwhelms low-lying land and often causes devastating loss of life and property.

Coastal flooding is categorized in three levels:

  • Minor: A slight amount of beach erosion will occur but no major damage is expected.
  • Moderate: A fair amount of beach erosion will occur as well as damage to some homes and businesses.

Coastal flooding caused by Hurricane Sandy ravaged the Jersey Shore in October 2012.


  • Did you know? In the United States, over half of the nation's economic productivity is located within coastal zones.1

Fluvial (River Flood)


There are two main types of riverine flooding:


In September 2013, heavy rain caused catastrophic river flooding along Colorado's Front Range.


  • Did you know? According to the Federal Emergency Management Association (FEMA), riverine flooding is the most common flood event.2

Pluvial (Surface Flood)


There are two common types of pluvial flooding:


Torrential rain caused extensive pluvial flooding in the United Kingdom during the summer of 2007.

Pluvial flooding often occurs in combination with coastal and fluvial flooding, and although typically only a few centimeters deep, a pluvial flood can cause significant property damage. 

  • Did you know? In the United Kingdom, pluvial flooding represents about one-third of all flood risk, with approximately 2 million people at risk.3

Looking Ahead


Want to learn more about assessing flood risk? Download my free guide below.


For other uses, see River (disambiguation).

"Rivers" redirects here. For other uses, see Rivers (disambiguation).








The river channel typically contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river.[4] Extensive braided rivers are now found in only a few regions worldwide,[citation needed] such as the South Island of New Zealand. They also occur on peneplains and some of the larger river deltas. Anastamosing rivers are similar to braided rivers and are quite rare. They have multiple sinuous channels carrying large volumes of sediment. There are rare cases of river bifurcation in which a river divides and the resultant flows ending in different seas. An example is the bifurcation of Nerodime River in Kosovo.

A river flowing in its channel is a source of energy which acts on the river channel to change its shape and form. In 1757, the German hydrologist Albert Brahms empirically observed that the submerged weight of objects that may be carried away by a river is proportional to the sixth power of the river flow speed.[5] This formulation is also sometimes called Airy's law.[6] Thus, if the speed of flow is doubled, the flow would dislodge objects with 64 times as much submerged weight. In mountainous torrential zones this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks. A river valley that was created from a U-shaped glaciated valley, can often easily be identified by the V-shaped channel that it has carved. In the middle reaches where a river flows over flatter land, meanders may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake or billabong. Rivers that carry large amounts of sediment may develop conspicuous deltas at their mouths. Rivers whose mouths are in saline tidal waters may form estuaries.

Throughout the course of the river, the total volume of water transported downstream will often be a combination of the free water flow together with a substantial volume flowing through sub-surface rocks and gravels that underlie the river and its floodplain (called the hyporheic zone). For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow.

Subsurface streams


Permanence of flow

Main article: Intermittent river

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.



Rivers have been classified by many criteria including their topography, their biotic status, and their relevance to white water rafting or canoeing activities.

Topographical classification



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:

  • Youthful river: A river with a steep gradient that has very few tributaries and flows quickly. Its channels erode deeper rather than wider. Examples are the Brazos, Trinity and Ebro rivers.
  • 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.
  • Old river: A river with a low gradient and low erosive energy. Old rivers are characterized by flood plains. Examples are the Yellow, lower Ganges, Tigris, Euphrates, Indus and lower Nile rivers.
  • Rejuvenated river: A river with a gradient that is raised by tectonic uplift. Examples are the Rio Grande and Colorado River.

The ways in which a river's characteristics vary between its upper and lower course are summarized by the Bradshaw model. Power-law relationships between channel slope, depth, and width are given as a function of discharge by "river regime".

Biotic classification

There are several systems of classification based on biotic conditions typically assigning classes from the most oligotrophic or unpolluted through to the most eutrophic or polluted.[9] Other systems are based on a whole eco-system approach such as developed by the New Zealand Ministry for the Environment.[10] In Europe, the requirements of the Water Framework Directive has led to the development of a wide range of classification methods including classifications based on fishery status[11] A system of river zonation used in francophone communities[12][13] divides rivers into three primary zones:

  • 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.
  • The rhithron is the upstream portion of the river that follows the crenon. It has relatively cool temperatures, high oxygen levels, and fast, turbulent, swift flow.
  • The potamon is the remaining downstream stretch of river. It has warmer temperatures, lower oxygen levels, slow flow and sandier bottoms.

Whitewater classification

The International Scale of River Difficulty is used to rate the challenges of navigation—particularly those with rapids. Class I is the easiest and Class VI is the hardest.

Stream order classification


In certain languages, distinctions are made among rivers based on their stream order. In French, for example, rivers that run to the sea are called fleuve, while other rivers are called rivière. For example, in Canada, the Churchill River in Manitoba is called la rivière Churchill as it runs to Hudson Bay, but the Churchill River in Labrador is called le fleuve Churchill as it runs to the Atlantic Ocean. As most rivers in France are known by their names only without the word rivière or fleuve (e.g. la Seine, not le fleuve Seine, even though the Seine is classed as a fleuve), one of the most prominent rivers in the Francophonie commonly known as fleuve is le fleuve Saint-Laurent (the Saint Lawrence River).

Since many fleuves are large and prominent, receiving many tributaries, the word is sometimes used to refer to certain large rivers that flow into other fleuves; however, even small streams that run to the sea are called fleuve (e.g. fleuve côtier, "coastal fleuve").



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.[14] 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 gasemissions, and to local cancer due to inhaling of particulates emitted by the transports.[15][16]


Rivers have been a source of food since pre-history.[17] 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. Most of the major cities of the world are situated on the banks of rivers. 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.

Fast flowing rivers and waterfalls are widely used as sources of energy, via watermills and hydroelectric plants. Evidence of watermills shows them in use for many hundreds of years, for instance in Orkney at Dounby Click Mill. Prior to the invention of steam power, watermills for grinding cereals and for processing wool and other textiles were common across Europe. In the 1890s the first machines to generate power from river water were established at places such as Cragside in Northumberland and in recent decades there has been a significant increase in the development of large scale power generation from water, especially in wet mountainous regions such as Norway.


In upland rivers, rapids with whitewater or even waterfalls occur. Rapids are often used for recreation, such as whitewater kayaking.[18]



Main article: River ecosystem

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 in time.


Main article: River chemistry

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

Further information: Brackish water



Main article: Flood

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.


Studying the flows of rivers is one aspect of hydrology.[19]


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.[20][21][22]



Main article: Streamflow



Fluvial erosion

In the youthful stage;

V-shaped valleys: example. River Liffey, Dublin, Ireland.

When the river is subject to vertical erosion, deepening the valley. Hydraulic action loosens and dislodges the rock. The rivers load further erodes its banks and the river bed. Over time, this will deepen the river bed and create steeper sides which are then weathered.

The steepened nature of the banks causes the sides of the valley to move downslope causing the valley to become V-Shaped.

Waterfalls also form in the youthful river valley. example. Powerscourt Waterfall, County Wicklow, Ireland.

Waterfalls usually form where a band of hard rock lies next to a layer of soft rock (easier to erode). Differential erosion occurs as the river can erode the soft rock easier than the hard rock, this leaves the hard rock more elevated and stands out from the river below. Hydraulic action and abrasion are what erodes the soft rock and the water to fall down to the river bed. A plunge pool forms at the bottom and deepens as a result of hydraulic action and abrasion.[23]

Sediment yield

Sediment yield is the total quantity of particulate matter (suspended or bedload) reaching the outlet of a drainage basin over a fixed time frame. Yield is usually expressed as kilograms per square kilometre per year. Sediment delivery processes are affected by a myriad of factors such as drainage area size, basin slope, climate, sediment type (lithology), vegetation cover, and human land use / management practices. The theoretical concept of the 'sediment delivery ratio' (ratio between yield and total amount of sediment eroded) captures the fact that not all of the sediment is eroded within a certain catchment that reaches out to the outlet (due to, for example, deposition on floodplains). Such storage opportunities are typically increased in catchments of larger size, thus leading to a lower yield and sediment delivery ratio.


Main article: River engineering





See also

See also: geography, water cycle, and drainage basin

Arts, entertainment, and media


  1. ^"GNIS FAQ". United States Geological Survey. Retrieved 26 January 2012. 
  2. ^"WordNet Search: River". The Trustees of Princeton University. Retrieved 2 October 2009. 
  3. ^"Domestic Names: Frequently Asked Question (FAQs), #17". United States Geological Survey. Retrieved 2 October 2009. 
  4. ^Walther, John V. (15 February 2013). Earth's Natural Resources. Jones & Bartlett Publishers. ISBN 978-1-4496-3234-2. 
  5. ^Garde, R. J. (1995). History of fluvial hydraulics. New Age Publishers. p. 14. ISBN 81-224-0815-X. OCLC 34628134. 
  6. ^Garde, R. J. (1995). History of fluvial hydraulics. New Age Publishers. p. 19. ISBN 81-224-0815-X. OCLC 34628134. 
  7. ^"Sand River" in Iraq is actually a rapid movement of ice blocks. Tampabayreview.com. Retrieved on 14 July 2016.
  8. ^Castree, Noel (2006). Questioning geography: fundamental debates. Wiley-Blackwell. pp. 84–85. ISBN 978-1-4051-0192-9. 
  9. ^River Classification scheme. sepa.org.uk
  10. ^NZ’s River Environment Classification system (REC). maf.govt.nz
  11. ^Noble, Richard and Cowx, Ian et al. (May 2002) Compilation and harmonisation of fish species classification. University of Hull, UK. A project under the 5th Framework Programme Energy, Environment and Sustainable Management. Key Action 1: Sustainable Management and Quality of Water
  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. 
  13. ^Hawkes, H.A. (1975). River zonation and classification. River ecology. Blackwell. pp. 312–374. 
  14. ^"WWF – The World's Rivers". panda.org.
  15. ^Meybeck, Michel (1993). "Riverine transport of atmospheric carbon: Sources, global typology and budget". Water, Air, & Soil Pollution. 70 (1–4): 443–463. doi:10.1007/BF01105015. 
  16. ^Albrecht, Achim (2003). "Validating riverine transport and speciation models using nuclear reactor-derived radiocobalt". Journal of Environmental Radioactivity. Elsevier Science Ltd. 66 (3): 295–307. doi:10.1016/S0265-931X(02)00133-9. PMID 12600761. 
  17. ^"National Museum of Prehistory-The Peinan Site-Settlements of the Prehistoric Times". nmp.gov.tw.
  18. ^Draper, Nick; Hodgson, Christopher (2008-11-20). Adventure Sport Physiology. John Wiley & Sons. ISBN 978-0-470-31913-0. 
  19. ^Cave, Cristi. "How a River Flows". Stream Biology and Ecology. Archived from the original on 1 January 2015. 
  20. ^Rosenberg, Matt (8 June 2006). "Do All Rivers Flow South?". About.com. 
  21. ^Rosenberg, Matt. "Rivers Flowing North: Rivers Only Flow Downhill; Rivers Do Not Prefer to Flow South". About.com. 
  22. ^Rydell, Nezette (16 March 1997). "Re: What determines the direction of river flow? Elevation, Topography, Gravity??". Earth Sciences. 
  23. ^"Landforms of the upper valley -". www.coolgeography.co.uk. Retrieved 2 December 2016. 

Further reading

Nile River delta, as seen from Earth orbit. The Nile is an example of a wave-dominated delta that has the classic Greek letter delta (Δ) shape after which river deltas were named.
A radar image of a 400-kilometre (250 mi) river of methane and ethane near the north pole of Saturn's moon Titan
Flash flooding caused by a large amount of rain falling in a short amount of time


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