![]() Such rivers are frequently found in regions with limestone geologic formations. Subterranean rivers flow underground in caves. Most but not all rivers flow on the surface. Subsurface rivers: subterranean and subglacial Rivers have been classified by many criteria including their topography, their biotic status, and their relevance to white water rafting or canoeing activities. For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow.Ī radar image of a 400-kilometre (250 mi) river of methane and ethane near the north pole of Saturn's moon Titan 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). Rivers whose mouths are in saline tidal waters may form estuaries. Rivers that carry large amounts of sediment may develop conspicuous deltas at their mouths. ![]() Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake or billabong. 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. 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 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. Thus, if the speed of flow is doubled, the flow would dislodge objects with 64 times as much submerged weight. This formulation is also sometimes called Airy's law. In 1757, 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. An example is the Nerodime River in Kosovo.Ī river flowing in its channel is a source of energy that acts on the river channel to change its shape and form. There are rare cases of river bifurcation in which a river divides into distributaries, and the resultant flows end in different seas. Anastamosing rivers are similar to braided rivers and are quite rare they have multiple sinuous channel - 1 carrying large volumes of sediment. The river channel typically contains a single stream, but some rivers flow as several interconnecting streams, producing a braided river, which occur on peneplains and some of the larger river deltas. Rivers can flow down mountains and hills through valleys and can create canyons or gorges, especially when traversing plains. ![]() In Earth science disciplines, potamology is the scientific study of rivers, while limnology is the study of inland waters in general.Ĭross-section of a river channel and its valley Towns often developed at the few locations suitable for fording, building bridges, or supporting ports many major cities, such as London, are located at the narrowest and most reliable sites at which a river could be crossed via bridges or ferries. In the pre-industrial era, larger rivers were a major obstacle to the movement of people, goods, and armies across regions. Most of the major cities of the world are situated on the banks of rivers, as they are (or were) depended upon as a vital source of drinking water, for food supply via fishing and agricultural irrigation, for shipping, as natural borders and/or defensive terrains, as a source of hydropower to drive machinery or generate electricity, for bathing, and as a means of disposing of waste. Rivers are significant to humankind since many human settlements and civilizations are built around sizeable rivers and streams. As a waterbody, rivers also serve crucial ecological functions by providing and feeding freshwater habitats for aquatic and semiaquatic fauna and flora, especially for migratory fish species, as well as enabling terrestrial ecosystems to thrive in the riparian zones. Rivers are also an important natural terraformer, as the erosive action of running water carves out rills, gullies, and valleys in the surface, as well as transferring silt and dissolved minerals downstream, forming river deltas and islands where the flow slows down. Rivers are often considered major features within a landscape however, they actually only cover around 0.1% of the land on Earth. Water from a drainage basin generally collects into a river through surface runoff from precipitation, meltwater released from natural ice and snowpacks, and other underground sources such as groundwater recharge and springs. Rivers are an important part of the water cycle. Melting toe of Athabasca Glacier, Jasper National Park, Alberta, Canada
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