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The flora and fauna of rivers use the aquatic habitats available, from torrential waterfalls through to lowland mires. Although many organisms are restricted to the fresh-water in rivers, some, such as Salmon and Hilsa have adapted to be able to survive both in rivers and in the sea.
[edit] Flooding
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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 flood stage. Human activity, however, has upset the natural way flooding occurs by walling off rivers, straightening their courses and by draining of natural wetlands.
[edit] Direction of flow
Some people think that most rivers flow from north to south.[6][7] Rivers in fact flow downhill regardless of direction, often in a complex meandering path involving all directions of the compass.[8][9][10]
Few major rivers in the continental US flow north, as most of the country is located in the watershed of the Pacific or Atlantic oceans or the Gulf of Mexico, with very few rivers flowing northward toward the Arctic Ocean, Great Lakes, or Hudson Bay. However, thousands of north-flowing rivers exist elsewhere, including such major watercourses as the Nile, Mackenzie, Rhine, Yenisei, Nelson, and Lena. Four of the ten longest river systems of the world flow mainly north.
Studying the flows of rivers is one aspect of hydrology.[11]
[edit] Rate of water flow
Volumetric flow rate, also called volume flow rate and rate of water flow, is the volume of water which passes through a given volume per unit time, measured in cubic meters per second (1 m³/s = 35.51 ft³/s) or cubic feet per second, sometimes gallons per second.
[edit] Management
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Rivers are often managed or controlled to make them more useful, or less disruptive, to human activity.
- Dams (see above) or weirs may be built to control the flow, store water, or extract energy.
- Levees, known as dikes in Europe, may be built to prevent river water from flowing on floodplains or floodways.
- Canals connect rivers to one another for water transfer or navigation.
- River courses may be modified to improve navigation, or straightened to increase the flow rate.
River management is a continuous activity as rivers tend to 'undo' the modifications made by people. Dredged channels silt up, sluice mechanisms deteriorate with age, levees and dams may suffer seepage or catastrophic failure. The benefits sought through managing rivers may often be offset by the social and economic costs of mitigating the bad effects of such management. As an example, in parts of the developed world, rivers have been confined within channels to free up flat flood-plain land for development. Floods can inundate such development at high financial cost and often with loss of life.
[edit] River lists
[edit] Rating systems
- International Scale of River Difficulty – The scale is used to rate the challenges of navigation—particularly those with rapids. Class I is the easiest and Class VI is the hardest.
- Strahler Stream Order – The Strahler Stream Order ranks rivers based on the connectivity and hierarchy of contributing tributaries. Headwaters are first order while Amazon River is twelfth order. Approximately 80 percent of the rivers and streams in the world are of the first and second order.
[edit] See also
- See also: geography, water cycle, and drainage basin
Wikimedia Commons has media related to:
[edit] Crossings
[edit] Transport
[edit] References
- , River, Wordnet
- , USGS GNIS FAQ, #17 What is the difference between “mountain,” “hill,” and “peak”; “lake” and “pond”; or “river” and “creek”?
- , Garde, R. J. (1995). History of fluvial hydraulics. New Age Publishers, p. 19. ISBN 812240815X.
- , Hans-Henrik Stølum: "River Meandering as a Self-Organization Process", Science 271 (5256), 1710
- , Fermat's last theorem, Simon Singh, 1997
- , Children's Misconceptions about Science. Operation Physics, American Institute of Physics (September 1998).
- , William C. Philips (February 1991). Earth Science Misconceptions.
- , Matt Rosenberg (2006-06-08). Do All Rivers Flow South?.
- , Matt Rosenberg. Rivers Flowing North: Rivers Only Flow Downhill; Rivers Do Not Prefer to Flow South.
- , Nezette Rydell (1997-03-16). Re: What determines the direction of river flow? Elevation, Topography, Gravity??. Earth Sciences.
- , Cristi Cave. How a River Flows. Stream Biology and Ecology.
[edit] Further reading
- Beyond the Bridges Life on American Rivers told by Riverlorian, Jerry Hay. [1]for more information
- Luna B. Leopold (1994). A View of the River. Harvard University Press. ISBN. — a non-technical primer on the geomorphology and hydraulics of water
- Jeffrey W. Jacobs "Rivers, Major World". Water Encyclopaedia.
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