Location of the Red River Delta region in Vietnam

The Red River Delta (Vietnamese: Đồng Bằng Sông Hồng) is the flat plain formed by the Red River and its distributaries joining in the Thai Binh River in northern Vietnam. The delta measuring some 15,000 square km is well protected by a network of dikes. It is an agriculturally rich area and densely populated. Most of the land is devoted to rice cultivation.^[1]

Eight provinces together with two municipalities, the capital Hà Nội and the main port Hải Phòng form the delta. It has a population of about ten million.

Water puppetry originated in the rice paddies here.

The region was bombed during the Vietnam War.

Provinces[link]

Notes and references[link]

1. ^ Whitfield, D. Historical and Cultural Dictionary of Vietnam. Metuchen, NJ: The Scarecrow Press, 1976

This article about a location in Vietnam is a stub. You can help Wikipedia by expanding it. v t e

Nile River delta, as seen from Earth orbit. The Nile is an example of a wave-dominated delta that has the classic Greek delta (Δ) shape after which river deltas were named.

A delta is a landform that is formed at the mouth of a river, where that river flows into an ocean, sea, estuary, lake, or reservoir. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river. Over long periods of time, this deposition builds the characteristic geographic pattern of a river delta.

Contrary to popular belief, the term delta was not coined by Herodotus^[1].

Formation[link]

River deltas form when a river carrying sediment reaches either (1) a body of standing water, such as a lake, ocean, or reservoir, (2) another river that cannot remove the sediment quickly enough to stop delta formation, or (3) an inland region where the water spreads out and deposits sediments. When the flow enters the standing water, it is no longer confined to its channel and expands in width. This flow expansion results in a decrease in the flow velocity, which diminishes the ability of the flow to transport sediment. As a result, sediment drops out of the flow and deposits. Over time, this single channel will build a deltaic lobe (such as the bird's-foot of the Mississippi or Ural River deltas), pushing its mouth further into the standing water. As the deltaic lobe advances, the gradient of the river channel becomes lower because the river channel is longer but has the same change in elevation (see slope). As the slope of the river channel decreases, it becomes unstable for two reasons. First, the water under the force of gravity will tend to flow in the most direct course down slope. If the river breaches its natural leaves (i.e., during a flood), it will spill out onto a new course with a shorter route to the ocean, thereby obtaining a more stable steeper slope.^[2] Second, as its slope gets lower, the amount of sheer stress on the bed will decrease, which will result in deposition of sediment within the channel and a rise in the channel bed relative to the floodplain. This will make it easier for the river to breach its levees and cut a new channel that enters the body of standing water at a steeper slope. Often when the channel does this, some of its flow can remain in the abandoned channel. When these channel switching events occur a mature delta will gain a distributary network.

Another way in which these distributary networks may form is from the deposition of mouth bars (mid-channel sand and/or gravel bars at the mouth of a river). When this mid-channel bar is deposited at the mouth of a river, the flow is routed around it. This results in additional deposition on the upstream end of the mouth-bar, which splits the river into two distributary channels. A good example of the result of this process is the Wax Lake Delta in Louisiana.

In both of these cases, depositional processes force redistribution of deposition from areas of high deposition to areas of low deposition. This results in the smoothing of the planform (or map-view) shape of the delta as the channels move across its surface and deposit sediment. Because the sediment is laid down in this fashion, the shape of these deltas approximates a fan. It is closer to an ideal fan the more often the flow changes course because more rapid changes in channel position results in more uniform deposition of sediment on the delta front. The Mississippi and Ural River deltas, with their bird's-feet, are examples of rivers that do not avulse often enough to form a symmetrical fan shape. Alluvial fan deltas, as seen in their name, avulse frequently and more closely approximate an ideal fan shape.

Types of deltas[link]

Lower Mississippi River landloss over time

Delta lobe switching in the Mississippi Delta,  4600 yrs BP,  3500 yrs BP,  2800 yrs BP,  1000 yrs BP,  300 yrs BP,  500 yrs BP,  current

Deltas are typically classified according to the main control on deposition, which is usually either a river, waves, or tides.^[3] These controls have a large effect on the shape of the resulting delta.

Wave-dominated deltas[link]

In wave dominated deltas, wave erosion controls the shape of the delta, although deposition still outweighs the amount of erosion and the delta is able to advance into the sea. Deltas of this form, such as the Nile Delta, tend to have a characteristic Greek-capital-delta shape Failed to parse (Missing texvc executable; please see math/README to configure.): \left(\Delta\right) .

The Ganges Delta in India and Bangladesh is the largest delta in the world and it is also one of the most fertile regions in the world.

Tide-dominated deltas[link]

Erosion is also an important control in tide dominated deltas, such as the Ganges Delta, which may be mainly submarine, with prominent sand bars and ridges. This tends to produce a "dendritic" structure.^[3] Tidal deltas behave differently from river- and wave-dominated deltas, which tend to have a few main distributaries. Once a wave- or river- distributary silts up, it is abandoned, and a new channel forms elsewhere. In a tidal delta, new distributaries are formed during times when there's a lot of water around – such as floods or storm surges. These distributaries slowly silt up at a pretty constant rate until they fizzle out.^[3]

Gilbert deltas[link]

A Gilbert delta (named after Grove Karl Gilbert) is a specific type of delta that is formed by coarse sediments, as opposed to gently-sloping muddy deltas such as that of the Mississippi. For example, a mountain river depositing sediment into a freshwater lake would form this kind of delta.^{[4] [5]} While some authors describe both lacustrine and marine locations of Gilbert deltas,^[4] others note that their formation is more characteristic of the freshwater lakes, where it is easier for the river water to mix with the lakewater faster (as opposed to the case of a river falling into the sea or a salt lake, where less dense fresh water brought by the river stays on top longer).^[6]

G.K. Gilbert himself first described this type of delta on Lake Bonneville in 1885.^[6] Elsewhere, similar structures can be found e.g. at the mouths of several creeks flowing into Okanagan Lake in British Columbia and forming prominent peninsulas at Naramata (49°35′30″N 119°35′30″W / 49.59167°N 119.59167°W / 49.59167; -119.59167), Summerland (49°34′23″N 119°37′45″W / 49.57306°N 119.62917°W / 49.57306; -119.62917), or Peachland (49°47′00″N 119°42′45″W / 49.7833333°N 119.7125°W / 49.7833333; -119.7125)

Estuaries[link]

Other rivers, particularly those located on coasts with significant tidal range, do not form a delta but enter into the sea in the form of an estuary. Notable examples include the Saint Lawrence River and the Tagus estuary.

Inland deltas[link]

Okavango Delta

In rare cases the river delta is located inside a large valley and is called an inverted river delta. Sometimes a river will divide into multiple branches in an inland area, only to rejoin and continue to the sea; such an area is known as an inland delta, and often occur on former lake beds. The Inner Niger Delta and Peace–Athabasca Delta are notable examples. The Amazon has also an inland delta before the island of Marajó.

In some cases a river flowing into a flat arid area splits into channels which then evaporate as it progresses into the desert. Okavango Delta in Botswana is one well-known example.

Sedimentary structure[link]

The formation of a delta consists of three main forms: the topset, foreset/frontset, and bottomset.^[4]

• The bottomset beds are created from the suspended sediment that settles out of the water as the river flows into the body of water and loses energy. The suspended load is carried out the furthest into the body of water than all other types of sediment creating a turbidite. These beds are laid down in horizontal layers and consist of smaller grains.
• The foreset beds in turn build over the bottomset beds as the main delta form advances. The foreset beds consist of the bed load that the river is moving along which consists of larger sediments that roll along the main channel. When it reaches the edge of the form, the bed load rolls over the edge, and builds up in steeply angled layers over the top of the bottomset beds. The angle of the outermost edge of the delta is created by the sediments angle of repose. As the foresets build outward (which make up the majority of the delta) they pile up and miniature landslides occur. This slope is created in this fashion as the bedload continues to be deposited and the delta moves outward. In cross section, one would see the foresets lying in angled, parallel bands, showing each stage of the creation of the delta.
• The topset beds in turn overlay the foresets, and are horizontal layers of smaller sediment size that form as the main channel of the river shifts elsewhere and the larger particles of the bed load no longer are deposited. As the channels move across the top of the delta, the suspended load settles out in horizontal beds over the top. The topset bed is subdivided into two regions: the upper delta plain and the lower delta plain. The upper delta plain is unaffected by the tide, while the boundary with the lower delta plain is defined by the upper limit of tidal influence. ^[7]

Deltas and alluvial fans[link]

Deltas are differentiated from alluvial fans in that deltas have a shallow slope, contain fine-grained sediment (sand and mud), and always flow into a body of water. Alluvial fans, on the other hand, are steep, have coarse-grained sediments (including boulders), and are dominated by debris flows and large floods; these floods are often flash floods. They can either flow onto a land surface, or into a body of water; in the latter case, they are called alluvial fan deltas.

Examples of notable deltas[link]

The most famous delta is that of the Nile River, and it is this delta from which the term is derived. The Ganges/Brahmaputra combination delta spans most of Bangladesh and West Bengal, empties into the Bay of Bengal and is the world's largest delta. Other rivers with notable deltas include, the Fly River, the Cauvery, the Niger River, the Tigris-Euphrates, the Rhine, the Po, the Rhône, the Danube, the Ebro, the Volga, the Lena, the Indus, the Ayeyarwady (Irrawaddy), the Mekong, the Huanghe, the Yangtze, the Sacramento-San Joaquin, the Mississippi, the Orinoco, and the Paraná.

Ecological threats to deltas[link]

Human activities, including diversion of water and the creation of dams for hydroelectric power or to create reservoirs can radically alter delta ecosystems. Dams block sedimentation which can cause the delta to erode away. The use of water upstream can greatly increase salinity levels as less fresh water flows to meet the salty ocean water. While nearly all deltas have been impacted to some degree by humans, the Nile Delta and Colorado River Delta are some of the most extreme examples of the ecological devastation caused to deltas by damming and diversion of water.

Deltas in the economy[link]

Ancient deltas are a benefit to the economy due to their well sorted sand and gravel. Sand and gravel is often quarried from these old deltas and used in concrete for highways, buildings, sidewalks, and even landscaping. More than 1 billion tons of sand and gravel are produced in the United States alone.^[8] Not all sand and gravel quarries are former deltas, but for ones that are, a lot of the sorting is already done by the power of water.

Deltas on Mars[link]

Researchers have found a number of examples of deltas that formed in Martian lakes. Finding deltas is a major sign that Mars once had a lot of water. Deltas have been found over a wide geographical range. Below are pictures of a few.^[9]

• 

  Delta in Ismenius Lacus quadrangle, as seen by THEMIS.

• 

  Delta in Lunae Palus quadrangle, as seen by THEMIS.

• 

  Delta in Margaritifer Sinus quadrangle as seen by THEMIS.

• Distributary fan-delta.jpg

  Probable delta in a crater to the NE of Holden Crater, as seen by Mars Global Surveyor. Image in Margaritifer Sinus quadrangle.

See also[link]

• Alluvial fan
• Avulsion (river)
• Estuary
• Formation of delta-shaped river basin
• Mega delta
• Regressive delta

References[link]

Wikimedia Commons has media related to: River deltas

External links[link]

• Louisiana State University Geology – World Deltas

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Red River may refer to:

Australia[link]

• Red River (Victoria)

Canada[link]

• Red River, Nova Scotia a community
• Red River of the North, a river flowing north through Minnesota, North Dakota, and Manitoba into Lake Winnipeg
  • Red River Cereal, a flax-based hot breakfast cereal
• Arctic Red River, a tributary of the Mackenzie River
• Red River (British Columbia), a tributary of the Kechika River

China[link]

• Red River (Asia), Hóng Hé (China) or Sông Hồng (Vietnam), flowing from China through Vietnam to the Gulf of Tonkin

New Zealand[link]

• Red River, New Zealand, a minor river on the North Island

Pakistan[link]

• Sutlej River, Punjab is sometimes known as the Red River.

United Kingdom[link]

• Red River, Cornwall, a minor river in west Cornwall discharging into the sea on the north coast
• Red River, Marazion, a minor river discharging into the sea on the south coast of west Cornwall

United States[link]

• Red River of the North, see above (under Canada)
• Red River (Kentucky), tributary of the Kentucky River
• Red River (Maine), tributary of the Fish River
• Red River (Mississippi River), tributary of the Mississippi River flowing between Texas and Oklahoma
  • Red River Parish, Louisiana
  • Red River County, Texas
• Red River (New Mexico), tributary of the Rio Grande
  • Red River, New Mexico, home of the Red River Ski Area
• Red River, New York, tributary of the Moose River
• Red River (Tennessee-Kentucky), tributary of the Cumberland River
• Red River (Wisconsin), tributary of the Wolf River
  • Red River, Wisconsin, a town
  • Red River, Shawano County, Wisconsin, an unincorporated community

Vietnam[link]

• Red River (Asia), Hóng Hé (China) or Sông Hồng (Vietnam), flowing from China through Vietnam to the Gulf of Tonkin
  • Red River Delta, an administrative region of Vietnam comprising provinces in the Red River's delta

Other uses[link]

• The Halys River (Western cultures and languages from the Greek) in Anatolia (Asia Minor), Turkish Kızılırmak ("Red River").
  • Red River (manga), a Japanese graphic novel series centered in Anatolia.
• Red River (1948 film), a 1948 American film.
• Red River (2009 film) or Hong He, a Chinese film.
• Red River, a fictional river in City of Heroes
• Operation Flashpoint: Red River, a video game for the Xbox 360, PC and PS3..
• Curse of the Red River, an album by the band Barren Earth

See also[link]

• Red River Hog, a species of wild pig from Africa
• Red River Campaign, a series of battles fought in the American Civil War in 1864
• Red River Rivalry, an annual football game between the University of Oklahoma and the University of Texas teams
• 2009 Red River flood
• Red River Colony, in the valley of the same in Manitoba
• Red River Floodway
• Red River cart
• Red River Trails
• Red River Rebellion, the Métis rebellion led by Louis Riel in present-day Manitoba
• Red River Valley, a remnant of glacial Lake Agassiz
• Little Red River (disambiguation)
• Red River Expedition (disambiguation), various expeditions of that name
• Rouge River (disambiguation)
• Colorado River or Río Colorado, which means "Red River"
• Rivière-Rouge, Quebec

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