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geomorphology Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or ...
, drainage systems, also known as river systems, are the patterns formed by the streams,
river A river is a natural flowing watercourse, usually freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the ...
s, and
lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much lar ...
s in a particular
drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
. They are governed by the topography of land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land.
Geomorphologist Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topography, topographic and bathymetry, bathymetric features created by physical, chemical or biological pro ...
s and hydrologists often view streams as part of drainage basins (and sub-basins). This is the topographic region from which a stream receives runoff, throughflow, and its saturated equivalent, groundwater flow. The number, size, and shape of the drainage basins varies and the larger and more detailed the
topographic map In modern mapping, a topographic map or topographic sheet is a type of map characterized by large-scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but histori ...
, the more information is available.Pidwirny, M., (2006). "The Drainage Basin Concept". ''Fundamentals of Physical Geography,'' 2nd Edition.
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Drainage patterns

Per the lie of channels, drainage systems can fall into one of several categories, known as drainage patterns. These depend on the
topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary s ...
and
geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ea ...
of the land. All forms of transitions can occur between parallel, dendritic, and trellis patterns.


Accordant versus discordant drainage patterns

A drainage system is described as accordant if its pattern correlates to the structure and relief of the landscape over which it flows. A discordant system or pattern does not correlate to the topography and geology of the area. Discordant drainage patterns are classified into two main types: ''
antecedent An antecedent is a preceding event, condition, cause, phrase, or word. The etymology is from the Latin noun ''antecedentem'' meaning "something preceding", which comes from the preposition ''ante'' ("before") and the verb ''cedere'' ("to go"). ...
'' and ''superimposed'', while ''ante position'' drainage patterns combine the two. In ''antecedent'' drainage, a river's vertical incision ability matches that of land uplift due to tectonic forces. ''Superimposed'' drainage develops differently: initially, a drainage system develops on a surface composed of 'younger' rocks, but due to denudation activities this surface of younger rocks is removed and the river continues to flow over a seemingly new surface, but one in fact made up of rocks of old geological formation.


Dendritic drainage pattern

Dendritic drainage systems (from
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
, ''dendrites'', "of or like a tree") are not straight and are the most common form of the drainage system. In this, there are many sub-tributaries (analogous to the twigs of a tree), which merge into tributaries of the main river (the branches and the trunk of the tree, respectively). They are seen to feed a river channel that matches and is strongly accordant to the overriding gradient of the land. Truly dendritic systems form in V-shaped valleys; as a result, the rock types must be impervious and non-porous.


Parallel drainage pattern

A parallel drainage system occurs on a common slope down linear ranges (or of rivers between linear series of
escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. The terms ''scarp'' and ''scarp face'' are often used interchangeably with ''esca ...
s, parallel, elongate landforms like outcropping resistant rock bands), typically following natural faults or erosion (such as prevailing wind scars). The watercourses run swift and straight, with very few tributaries, and all flow in the same direction. This system forms on very long, uniform slopes, for instance, high rivers flowing southeast from the Aberdare Mountains in Kenya and many rivers of
Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...
. This sometimes indicates a major fault that cuts across an area of steeply folded bedrock.


Trellis drainage pattern

The geometry of a trellis drainage system is similar to that of a common garden
trellis Trellis may refer to: Structures * Trellis (architecture), an architectural structure often used to support plants (especially vineyards) * Trellis drainage pattern, a drainage system Technology * Trellis (graph), a special kind of graph used ...
. Along a strike valley, smaller tributaries feed into the steep slopes of mountainsides. These tributaries enter the main river about perpendicular, causing a trellis-like appearance of the system. They form where hard and soft formations exist on both banks of the main river, and are reflective of height, accentuated by erosion. Trellis drainage is characteristic of folded mountains, such as the
Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. The ...
in North America and in the north part of
Trinidad Trinidad is the larger and more populous of the two major islands of Trinidad and Tobago. The island lies off the northeastern coast of Venezuela and sits on the continental shelf of South America. It is often referred to as the southernmos ...
.


Rectangular drainage pattern

Rectangular drainage develops on rocks that are of approximately uniform resistance to
erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is di ...
, but which have two directions of jointing at approximately right angles or 90 degrees. The joints are usually less resistant to erosion than the bulk rock so erosion tends to preferentially open the joints and streams eventually develop along the joints. The result is a stream system in which streams consist mainly of straight line segments with right-angle bends and tributaries join larger streams at right angles. This pattern can be found with the Arun River in Nepal.


Radial drainage pattern

In a radial drainage system, the streams radiate outwards from a central high point. Volcanos usually have archetypal features on which this commonly develops are modest or hard domes pattern develops when streams flow in many general directions (meaning quite long-term) In India, the
Amarkantak Amarkantak (NLK ''Amarakaṇṭaka'') is a pilgrim town and a Nagar Panchayat in Anuppur, Madhya Pradesh, India. The Amarkantak region is a unique natural heritage area and is the meeting point of the Vindhya and the Satpura Ranges, with the Maik ...
range and Ramgarh crater are most archetypal; and Dogu'a Tembien in
Ethiopia Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the Er ...
.


Centripetal drainage pattern

When the streams converge at a point, which is generally a depression or a basin they form centripetal or inland drainage pattern.


Deranged drainage pattern

A deranged drainage system is a drainage system in
drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
s where there is no coherent pattern to the rivers and lakes. These can form in areas with extensive limestone deposits, where surface streams can disappear into the groundwater via caves and subterranean drainage routes. They can also form in areas where there has been much geological disruption. A classic example is the Canadian Shield. During the last ice age, the
topsoil Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs. Description Topsoil is composed of mineral particles and organic matte ...
was scraped off, leaving mostly bare rock. The melting of the glaciers left land with many irregularities of elevation and a great deal of water to collect in the low points, explaining the large number of lakes which are found in
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...
. The drainage basins are young and are still sorting themselves out. Eventually the system will stabilize.


Annular drainage pattern

In an annular drainage pattern, streams trace a tangential or greater concentric path along a belt of weak rock so, with others, a roughly traced out ring can be seen. It is best displayed by streams draining a maturely dissected structural dome or basin where erosion has exposed rimming
sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
strata of greatly varying degrees of hardness, as in the Red Valley, which nearly encircles the domal structure of the
Black Hills The Black Hills ( lkt, Ȟe Sápa; chy, Moʼȯhta-voʼhonáaeva; hid, awaxaawi shiibisha) is an isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, United States. Black Elk P ...
of
South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...
.


Angular drainage pattern

Angular drainage patterns form where
bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of be ...
joints and faults intersect at angles other than rectangular drainage patterns. Angles can be more or less than 90 degrees.


Integrated drainage

An integrated drainage is a mature drainage system characteristic of arid climates. It is formed by coalescing of individual basins formerly separated by high ground, such as mountains or ridges. Headward erosion from a lower basin may breach the barrier, as may spilling over from a higher basin due to
aggradation Aggradation (or alluviation) is the term used in geology for the increase in land elevation, typically in a river system, due to the deposition of sediment. Aggradation occurs in areas in which the supply of sediment is greater than the amount o ...
(accumulation of sediments in the basin). The effect of integration of a drainage system is to replace local higher base levels with a single lower base level. An example of an integrated drainage is the area drained by the Rio Grande River. The sedimentary basins forming the modern Rio Grande Valley were not integrated into a single river system draining into the Gulf of Mexico until relatively recent geologic time. Instead, the basins formed by the opening of the Rio Grande rift were initially bolsons, with no external drainage and a central
playa Playa (plural playas) may refer to: Landforms * Endorheic basin, also known as a sink, alkali flat or sabkha, a desert basin with no outlet which periodically fills with water to form a temporary lake * Dry lake, often called a ''playa'' in the so ...
. An axial river existed in the Espanola Basin as early as 13 million years ago, reaching the Santo Domingo Basin by 6.9 million years ago. However, at this time, the river drained into a playa in the southern Albuquerque Basin where it deposited the Popotosa Formation. The upper reach of this river corresponded to the modern Rio Chama, but by 5 million years ago, an ancestral Rio Grande draining the eastern San Juan Mountains had joined the ancestral Rio Chama. The ancestral Rio Grande progressively integrated basins to the south, reaching the Palomas basin by 4.5 million years ago, the Mesilla basin by 3.1 million years, to Texas by 2.06 million years, and finally joining the Pecos River at 800,000 years to drain into the Gulf of Mexico. Volcanism in the Taos Plateau reduced drainage from the San Luis basin until a spillover event 440,000 years ago that drained
Lake Alamosa Lake Alamosa is a former lake in Colorado. It existed from the Pliocene to the middle Pleistocene in the San Luis Valley, fed by glacial meltwater from surrounding mountain ranges. Water levels waxed and waned with the glacial stages until at hig ...
and fully reintegrated the San Luis basin into the Rio Grande basin. Integrated drainages were widespread in western North America in the
Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...
and
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...
, and there is evidence of integrated drainages on the surface of
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmos ...
.


See also

*
Distributary A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel. Distributaries are a common feature of river deltas. The phenomenon is known as river bifurcation. The opposite of a distribut ...
* Integrated catchment management *
List of unusual drainage systems The following is a list of unusual drainage systems. List Bifurcation rivers (active) * The Casiquiare canal – natural waterway connecting the Orinoco and Amazon rivers. * The Chicago River and Calumet River artificially divert water from t ...
*
River bifurcation River bifurcation (from la, furca, fork) occurs when a river flowing in a single stream separates into two or more separate streams (called distributaries) which then continue downstream. Some rivers form complex networks of distributaries, ty ...
* Stream capture


References


External links


StarHydro – software tool that covers concepts of fluvial geomorphology and watershed hydrology
{{Authority control Drainage basins Geomorphology Limnology Hydrology Rivers Water streams Water and the environment