A river begins at a source (or more often several sources) and ends at a mouth, following a path called a course. The water in a river is usually confined to a channel, made up of a stream bed between banks. In larger rivers there is 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.
Rivers can flow down mountains, through valleys (depressions) or along plains, and can create canyons or gorges.
The term upriver (or upstream) refers to the direction towards the source of the river, i.e. against the direction of flow. Likewise, the term downriver (or downstream) describes the direction towards the mouth of the river, in which the current flows.
The river channel typically contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river. Extensive braided rivers are now found in only a few regions worldwide, 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 also quite rare. They have multiple sinuous channels carrying large volumes of sediment. There are only two cases in the world of rivers dividing and the resultant flows ending in different seas: one of these 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. This formulation is also sometimes called Airy's law. 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. In U-shaped glaciated valleys, the subsequent river 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.
Read more about this topic: River
Other articles related to "topography":
... standard diagnostic test for PMD is corneal topography ... However, it may not as specific as corneal pachymetry, because corneal topography only evaluates the degree and distribution of surface irregularities on the cornea, not the thickness of the cornea ... Corneal topography may show a "crab claw-like" appearance, a finding that is seen in both keratoconus and in pellucid marginal degeneration ...
... in elevation and the highest ratio between the topography and geoid height are over the southeastern part of the chain, falling with distance from the hotspot, particularly at the intersection of the Molokai and ... the swell, as well as lack of detected heat flow, caused scientists to suggest dynamic topography as the cause, in which the motion of the hot and buoyant mantle plume supports the high surface ...
... Topography has been applied to different science fields ... In neuroscience, the neuroimaging discipline uses techniques such as EEG topography for brain mapping ... In ophthalmology, corneal topography is used as a technique for mapping the surface curvature of the cornea ...
... The topography of the district is typical representative of an alluvial plain ... It owes its origin to the aggravation work of the Satluj River ...
... Macedonia also has scenic mountains ... They belong to two different mountain ranges the first is the Šar Mountains that continues to the West Vardar/Pelagonia group of mountains (Baba Mountain, Nidže, Kozuf and Jakupica), also known as the Dinaric range ...
Famous quotes containing the word topography:
“That the mere matter of a poem, for instanceits subject, its given incidents or situation; that the mere matter of a picturethe actual circumstances of an event, the actual topography of a landscapeshould be nothing without the form, the spirit of the handling, that this form, this mode of handling, should become an end in itself, should penetrate every part of the matter;Mthis is what all art constantly strives after, and achieves in different degrees.”
—Walter Pater (18391894)