River delta

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Sacramento (California) Delta at flood stage, early-March 2009 Sacramento Delta at flood stage, 2009.jpg
Sacramento (California) Delta at flood stage, early-March 2009

A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. [1] [2] This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment. The size and shape of a delta is controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment. [3] [4] The size, geometry, and location of the receiving basin also plays an important role in delta evolution. River deltas are important in human civilization, as they are major agricultural production centers and population centers. They can provide coastline defense and can impact drinking water supply. [5] They are also ecologically important, with different species' assemblages depending on their landscape position.

Landform A natural feature of the solid surface of the Earth or other planetary body

A landform is a natural feature of the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Typical landforms include hills, mountains, plateaus, canyons, and valleys, as well as shoreline features such as bays, peninsulas, and seas, including submerged features such as mid-ocean ridges, volcanoes, and the great ocean basins.

Deposition (geology) Geological process in which sediments, soil and rocks are added to a landform or land mass

Deposition is the geological process in which sediments, soil and rocks are added to a landform or land mass. Wind, ice, water, and gravity transport previously weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.

Sediment Particulate solid matter that is deposited on the surface of land

Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation and if buried, may eventually become sandstone and siltstone.

Contents

Formation

Delta forms where river meets lake Delta Formation.svg
Delta forms where river meets lake

River deltas form when a river carrying sediment reaches either (1) a body of 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. The tidal currents also cannot be too strong, as sediment would wash out into the water body faster than the river deposits it. The river must carry enough sediment to layer into deltas over time. The river's velocity decreases rapidly, causing it to deposit the majority, if not all, of its load. This alluvium builds up to form the river delta. [7] 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 builds a deltaic lobe (such as the bird's-foot of the Mississippi or Ural river deltas), pushing its mouth 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).

Reservoir A storage space for fluids

A reservoir is, most commonly, an enlarged natural or artificial lake, pond or impoundment created using a dam or lock to store water.

Alluvium Loose soil or sediment that is eroded and redeposited in a non-marine setting

Alluvium is loose, unconsolidated soil or sediment that has been eroded, reshaped by water in some form, and redeposited in a non-marine setting. Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel. When this loose alluvial material is deposited or cemented into a lithological unit, or lithified, it is called an alluvial deposit.

Sediment transport The movement of solid particles, typically by gravity and fluid entrainment

Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems where the particles are clastic rocks, mud, or clay; the fluid is air, water, or ice; and the force of gravity acts to move the particles along the sloping surface on which they are resting. Sediment transport due to fluid motion occurs in rivers, oceans, lakes, seas, and other bodies of water due to currents and tides. Transport is also caused by glaciers as they flow, and on terrestrial surfaces under the influence of wind. Sediment transport due only to gravity can occur on sloping surfaces in general, including hillslopes, scarps, cliffs, and the continental shelf—continental slope boundary.

As the slope of the river channel decreases, it becomes unstable for two reasons. First, gravity makes the water flow in the most direct course down slope. If the river breaches its natural levees (i.e., during a flood), it spills out into a new course with a shorter route to the ocean, thereby obtaining a more stable steeper slope. [8] Second, as its slope gets lower, the amount of shear stress on the bed decreases, which results in deposition of sediment within the channel and a rise in the channel bed relative to the floodplain. This makes 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 remains in the abandoned channel. When these channel-switching events occur, a mature delta develops a distributary network.

Distributary stream that branches off and flows away from a main stream channel

A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel. They are a common feature of river deltas. The phenomenon is known as river bifurcation. The opposite of a distributary is a tributary. Distributaries usually occur as a stream nears a lake or an ocean, but they can occur inland as well, such as on alluvial fans or when a tributary stream bifurcates as it nears its confluence with a larger stream. In some cases, a minor distributary can divert so much water from the main channel that it can become the main route.

Another way these distributary networks form is from 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 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. The more often the flow changes course, the shape develops as closer to an ideal fan, 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 by their name, avulse frequently and more closely approximate an ideal fan shape.

In sedimentary geology and fluvial geomorphology, avulsion is the rapid abandonment of a river channel and the formation of a new river channel. Avulsions occur as a result of channel slopes that are much less steep than the slope that the river could travel if it took a new course.

Alluvial fan A fan- or cone-shaped deposit of sediment crossed and built up by streams

Alluvial fans are triangular-shaped deposits of water-transported material, often referred to as alluvium. They are an example of an unconsolidated sedimentary deposit and tend to be larger and more prominent in arid to semi-arid regions. These alluvial fans typically form in elevated or even mountainous regions where there is a rapid change in slope from a high to low gradient. The river or stream carrying the sediment flows at a relatively high velocity due to the high slope angle which is why coarse material is able to remain in the flow. When the slope decreases rapidly into a relatively plain or plateau, the stream loses the energy it needs to move its sediment. Deposition subsequently occurs and the sediment ultimately spreads out, creating an alluvial fan. Three primary zones occur within an alluvial fan which includes the proximal fan, medial fan, and the distal fan.

Most large river deltas discharge to intra-cratonic basins on the trailing edges of passive margins due to the majority of large rivers such as the Mississippi, Nile, Amazon, Ganges, Indus, and Yangtze discharging along passive continental margins. [9] This phenomenon is due to three big factors: topography, basin area, and basin elevation. [9] Topography along passive margins tend to be more gradual and widespread over a greater area enabling sediment to pile up and accumulate overtime to form large river deltas. Topography along active margins tend to be steeper and less widespread, which results in sediments not having the ability to pile up and accumulate due to the sediment traveling into a steep subduction trench rather than a shallow continental shelf.

There are many other smaller factors that could explain why the majority of river deltas form along passive margins rather than active margins. Along active margins, orogenic sequences cause tectonic activity to form over-steepened slopes, brecciated rocks, and volcanic activity resulting in delta formation to exist closer to the sediment source. [9] [10] When sediment does not travel far from the source, sediments that build up are coarser grained and more loosely consolidated, therefore making delta formation more difficult. Tectonic activity on active margins causes the formation of river deltas to form closer to the sediment source which may affect channel avulsion, delta lobe switching, and auto cyclicity. [10] Active margin river deltas tend to be much smaller and less abundant but may transport similar amounts of sediment. [9] However, the sediment is never piled up in thick sequences due to the sediment traveling and depositing in deep subduction trenches. [9]

Types of deltas

Lower Mississippi River land loss over time Lower Mississippi River landloss over time.jpg
Lower Mississippi River land loss 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 Mississippi Delta Lobes.jpg
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 a combination of river, wave, and tidal processes, [11] depending on the strength of each. [12] The other two factors that play a major role are landscape position and the grain size distribution of the source sediment entering the delta from the river. [13]

Wave-dominated deltas

In wave dominated deltas, wave-driven sediment transport controls the shape of the delta, and much of the sediment emanating from the river mouth is deflected along the coast line. [11] The relationship between waves and river deltas is quite variable and largely influenced by the deepwater wave regimes of the receiving basin. With a high wave energy near shore and a steeper slope offshore, waves will make river deltas smoother. Waves can also be responsible for carrying sediments away from the river delta, causing the delta to retreat. [5] For deltas that form further upriver in an estuary, there are complex yet quantifiable linkages between winds, tides, river discharge, and delta water levels. [14] [15]

The Ganges Delta in India and Bangladesh is the largest delta in the world, and one of the most fertile regions in the world. Ganges River Delta, Bangladesh, India.jpg
The Ganges Delta in India and Bangladesh is the largest delta in the world, and one of the most fertile regions in the world.

Tide-dominated deltas

Erosion is also an important control in tide-dominated deltas, such as the Ganges Delta, which may be mainly submarine, with prominent sandbars and ridges. This tends to produce a "dendritic" structure. [16] Tidal deltas behave differently from a river- and wave-dominated deltas, which tend to have a few main distributaries. Once a wave- or river-dominated distributary silts up, it is abandoned, and a new channel forms elsewhere. In a tidal delta, new distributaries are formed during times when there is a lot of water around – such as floods or storm surges. These distributaries slowly silt up at a more or less constant rate until they fizzle out. [16]

Gilbert deltas

A Gilbert delta (named after Grove Karl Gilbert) is a type of delta formed from 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. [17] [18] While some authors describe both lacustrine and marine locations of Gilbert deltas, [17] 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). [19]

Gilbert himself first described this type of delta on Lake Bonneville in 1885. [19] Elsewhere, similar structures occur, for example, at the mouths of several creeks that flow into Okanagan Lake in British Columbia and forming prominent peninsulas at Naramata, Summerland, and Peachland.

Tidal freshwater deltas

A tidal freshwater delta [20] is a sedimentary deposit formed at the boundary between an upland stream and an estuary, in the region known as the "subestuary". [21] Drowned coastal river valleys that were inundated by rising sea levels during the late Pleistocene and subsequent Holocene tend to have dendritic estuaries with many feeder tributaries. Each tributary mimics this salinity gradient from their brackish junction with the mainstem estuary up to the fresh stream feeding the head of tidal propagation. As a result, the tributaries are considered to be "subestuaries". The origin and evolution of a tidal freshwater delta involves processes that are typical of all deltas [4] as well as processes that are unique to the tidal freshwater setting. [22] [23] The combination of processes that create a tidal freshwater delta result in a distinct morphology and unique environmental characteristics. Many tidal freshwater deltas that exist today are directly caused by the onset of or changes in historical land use, especially deforestation, intensive agriculture, and urbanization. [24] These ideas are well illustrated by the many tidal freshwater deltas prograding into Chesapeake Bay along the east coastline of the United States. Research has demonstrated that the accumulating sediments in this estuary derive from post-European settlement deforestation, agriculture, and urban development. [25] [26] [27]

Estuaries

Other rivers, particularly those 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 Gulf of Saint Lawrence and the Tagus estuary.

Inland deltas

Okavango Delta OkavangoDelta.png
Okavango Delta

In rare cases the river delta is located inside a large valley and is called an inverted river delta. Sometimes a river divides into multiple branches in an inland area, only to rejoin and continue to the sea. Such an area is called an inland delta, and often occurs on former lake beds. The Inner Niger Delta and Peace–Athabasca Delta are notable examples. The Amazon also has an inland delta before the island of Marajó, and the Danube has one in the valley on the Slovak-Hungarian border between Bratislava and Iža.

In some cases, a river flowing into a flat arid area splits into channels that evaporate as it progresses into the desert. The Okavango Delta in Botswana is one example.

Mega deltas

The generic term mega delta can be used to describe very large Asian river deltas, such as the Yangtze, Pearl, Red, Mekong, Irrawaddy, Ganges-Brahmaputra, and Indus.

Sedimentary structure

Delta on Kachemak Bay at low tide Line5066 - Flickr - NOAA Photo Library.jpg
Delta on Kachemak Bay at low tide

The formation of a delta is complicated, multiple, and cross-cutting over time, but in a simple delta three main types of bedding may be distinguished: the bottomset beds, foreset/frontset beds, and topset beds. This three part structure may be seen in small scale by crossbedding. [17] [28]

Examples of deltas

The Ebro River delta at the Mediterranean Sea EbroRiverDelta ISS009-E-09985.jpg
The Ebro River delta at the Mediterranean Sea

The Ganges-Brahmaputra Delta, which spans most of Bangladesh and West Bengal, India empties into the Bay of Bengal, is the world's largest delta.

The St. Clair River delta, between the Canadian province of Ontario and the U.S. state of Michigan, is the largest delta emptying into a body of fresh water.

Other deltas

Ecological threats to deltas

Human activities, such as 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. Construction, irrigation, and land alteration have impacted delta formation. As humans have altered surface roughness, runoff, and groundwater storage, studies have shown river delta retreat. However, historical data documents show that during the Roman Empire and Little Ice Age (times where there was considerable anthropogenic pressure), there were significant sediment accumulation in deltas. The industrial revolution has only amplified the impact of humans on delta growth and retreat. [31]

Deltas in the economy

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. [32] Not all sand and gravel quarries are former deltas, but for ones that are, much of the sorting is already done by the power of water.

As lowlands often adjacent to urban areas, deltas often comprise extensive industrial and commercial areas as well as agricultural land. These uses are often in conflict. The Fraser Delta in British Columbia, Canada, includes the Vancouver Airport and the Roberts Bank Superport and the Annacis Island industrial zone, and a mix of commercial, residential and agricultural land. Space is so limited in the Lower Mainland region, and in British Columbia in general, which is very mountainous, that the Agricultural Land Reserve was created to preserve agricultural land for food production.

Deltas on Mars

Researchers have found a number of examples of deltas that formed in Martian lakes. Finding deltas is a major sign that Mars once had large amounts of water. Deltas have been found over a wide geographical range. Below are pictures of a few. [33]

See also

Related Research Articles

Estuary A partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.

Lagoon A shallow body of water separated from a larger body of water by barrier islands or reefs

A lagoon is a shallow body of water separated from a larger body of water by barrier islands or reefs. Lagoons are commonly divided into coastal lagoons and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. Lagoons are common coastal features around many parts of the world.

Braided river A network of river channels separated by small, and often temporary, islands called [[braid bar]]s

A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in British usage, aits or eyots. Braided streams occur in rivers with low speed, low slope, and/or large sediment load. Braided channels are also typical of environments that dramatically decrease channel depth, and consequently channel velocity, such as river deltas, alluvial fans, and peneplains.

Shoal A natural landform that rises from the bed of a body of water to near the surface and is covered by unconsolidated material

In oceanography, geomorphology, and earth sciences, a shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body of water to near the surface. Often it refers to those submerged ridges, banks, or bars that rise near enough to the surface of a body of water as to constitute a danger to navigation. Shoals are also known as sandbanks, sandbars, or gravelbars. Two or more shoals that are either separated by shared troughs or interconnected by past or present sedimentary and hydrographic processes are referred to as a shoal complex.

Longshore drift Sediment moved by the longshore current

Longshore drift from longshore current is a geological process that consists of the transportation of sediments along a coast parallel to the shoreline, which is dependent on oblique incoming wind direction. Oblique incoming wind squeezes water along the coast, and so generates a water current which moves parallel to the coast. Longshore drift is simply the sediment moved by the longshore current. This current and sediment movement occur within the surf zone.

Phosphorite non-detrital sedimentary rock which contains high amounts of phosphate bearing minerals

Phosphorite,phosphate rock or rock phosphate is a non-detrital sedimentary rock which contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pentoxide (P2O5). Marketed phosphate rock is enriched ("beneficiated") to at least 28%, often more than 30% P2O5. This occurs through washing, screening, de-liming, magnetic separation or flotation. By comparison, the average phosphorus content of sedimentary rocks is less than 0.2%. The phosphate is present as fluorapatite Ca5(PO4)3F typically in cryptocrystalline masses (grain sizes < 1 μm) referred to as collophane-sedimentary apatite deposits of uncertain origin. It is also present as hydroxyapatite Ca5(PO4)3OH or Ca10(PO4)6(OH)2, which is often dissolved from vertebrate bones and teeth, whereas fluorapatite can originate from hydrothermal veins. Other sources also include chemically dissolved phosphate minerals from igneous and metamorphic rocks. Phosphorite deposits often occur in extensive layers, which cumulatively cover tens of thousands of square kilometres of the Earth's crust.

Tidal marsh Marsh subject to tidal change in water

A tidal marsh is a marsh found along rivers, coasts and estuaries which floods and drains by the tidal movement of the adjacent estuary, sea or ocean. Tidal marshes experience many overlapping persistent cycles, including diurnal and semi-diurnal tides, day-night temperature fluctuations, spring-neap tides, seasonal vegetation growth and decay, upland runoff, decadal climate variations, and centennial to millennial trends in sea level and climate. They are also impacted by transient disturbances such as hurricanes, floods, storms, and upland fires.

Meander A sinuous bend in a series in the channel of a river

A meander is one of a series of regular sinuous curves, bends, loops, turns, or windings in the channel of a river, stream, or other watercourse. It is produced by a stream or river swinging from side to side as it flows across its floodplain or shifts its channel within a valley. A meander is produced by a stream or river as it erodes the sediments comprising an outer, concave bank and deposits this and other sediment downstream on an inner, convex bank which is typically a point bar. The result of sediments being eroded from the outside concave bank and their deposition on an inside convex bank is the formation of a sinuous course as a channel migrates back and forth across the down-valley axis of a floodplain. The zone within which a meandering stream shifts its channel across either its floodplain or valley floor from time to time is known as a meander belt. It typically ranges from 15 to 18 times the width of the channel. Over time, meanders migrate downstream, sometimes in such a short time as to create civil engineering problems for local municipalities attempting to maintain stable roads and bridges.

Cross-bedding

In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The original depositional layering is tilted, such tilting not being the result of post-depositional deformation. Cross-beds or "sets" are the groups of inclined layers, which are known as cross-strata.

Depositional environment The combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment

In geology, depositional environment or sedimentary environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record. In most cases the environments associated with particular rock types or associations of rock types can be matched to existing analogues. However, the further back in geological time sediments were deposited, the more likely that direct modern analogues are not available.

A foreset bed is one of the main parts of a river delta. It is the inclined part of a delta that is found at the end of the stream channel as the delta sediment is deposited along the arcuate delta front. As the sediments are deposited on a sloping surface the resulting bedding is not horizontal, but dips in the direction of current flow toward deeper water. A cross-section of a delta shows the cross bedding in the direction of stream flow into the still water.

Sedimentary structures include all kinds of features formed at the time of deposition. Sediments and sedimentary rocks are characterized by bedding, which occurs when layers of sediment, with different particle sizes are deposited on top of each other. These beds range from millimeters to centimeters thick and can even go to meters or multiple meters thick.

Wax Lake

Wax Lake was a lake in St. Mary Parish, Louisiana that was converted into an outlet channel to divert water from the Atchafalaya River to the Gulf of Mexico.

River mouth end of a river

A river mouth is the part of a river where the river debouches into another river, a lake, a reservoir, a sea, or an ocean.

Bar (river morphology) An elevated region of sediment in a river that has been deposited by the flow

A bar in a river is an elevated region of sediment that has been deposited by the flow. Types of bars include mid-channel bars, point bars, and mouth bars. The locations of bars are determined by the geometry of the river and the flow through it. Bars reflect sediment supply conditions, and can show where sediment supply rate is greater than the transport capacity.

A mouth bar is a bar in a river that is typically created in the middle of a channel in a river delta. It is created by a positive feedback between mid-channel deposition and flow divergence. As the flow diverges near the ocean, sediment settles out in the channel and creates an incipient mouth bar. As flow is routed around the incipient bar, additional sediment is deposited on the incipient bar. This continued process results in the formation of a full-fledged mouth bar, which causes the channel to bifurcate. This continued process leads to the characteristic fractal tree pattern found in some prograding river-dominated deltas.

A contourite is a sedimentary deposit commonly formed on continental rise to lower slope settings, although they may occur anywhere that is below storm wave base. Countourites are produced by thermohaline-induced deepwater bottom currents and may be influenced by wind or tidal forces. The geomorphology of contourite deposits is mainly influenced by the deepwater bottom-current velocity, sediment supply, and seafloor topography.

References

  1. Miall, A. D. 1979. Deltas. in R. G. Walker (ed) Facies Models. Geological Association of Canada, Hamilton, Ontario.
  2. Elliot, T. 1986. Deltas. in H. G. Reading (ed.). Sedimentary environments and facies. Backwell Scientific Publications, Oxford.
  3. Blum, M.D.; Tornqvist, T.E. (2000). "Fluvial responses to climate and sea-level change: a review and look forward". Sedimentology. 47: 2–48. doi:10.1046/j.1365-3091.2000.00008.x.
  4. 1 2 Pasternack, Gregory B.; Brush, Grace S.; Hilgartner, William B. (2001-04-01). "Impact of historic land-use change on sediment delivery to a Chesapeake Bay subestuarine delta". Earth Surface Processes and Landforms . 26 (4): 409–427. doi:10.1002/esp.189. ISSN   1096-9837.
  5. 1 2 Anthony, Edward J. (2015-03-01). "Wave influence in the construction, shaping and destruction of river deltas: A review". Marine Geology. 361: 53–78. doi:10.1016/j.margeo.2014.12.004.
  6. "How a Delta Forms Where River Meets Lake". 2014-08-12. Retrieved 2017-12-12.
  7. "Dr. Gregory B. Pasternack – Watershed Hydrology, Geomorphology, and Ecohydraulics :: TFD Modeling". pasternack.ucdavis.edu. Retrieved 2017-06-12.
  8. Slingerland, R. and N. D. Smith (1998), "Necessary conditions for a meandering-river avulsion," Geology (Boulder), 26, 435–438.
  9. 1 2 3 4 5 Milliman, J. D.; Syvitski, J. P. M. (1992). "Geomorphic/Tectonic Control of Sediment Discharge to the Ocean: The Importance of Small Mountainous Rivers". The Journal of Geology. 100 (5): 525–544. doi:10.1086/629606. JSTOR   30068527.
  10. 1 2 Goodbred, S. L.; Kuehl, S. A. (2000). "The significance of large sediment supply, active tectonism, and eustasy on margin sequence development: Late Quaternary stratigraphy and evolution of the Ganges-Brahmaputra delta". Sedimentary Geology. 133 (3–4): 227–248. doi:10.1016/S0037-0738(00)00041-5.
  11. 1 2 Galloway, W.E., 1975, Process framework for describing the morphologic and stratigraphic evolution of deltaic depositional systems, in Brousard, M.L., ed., Deltas, Models for Exploration: Houston Geological Society, Houston, Texas, pp. 87–98.
  12. Perillo, G. M. E. 1995. Geomorphology and Sedimentology of Estuaries. Elsevier Science B.V., New York.
  13. Orton, G.J.; Reading, H.G. (1993). "Variability of deltaic processes in terms of sediment supply, with particular emphasis on grain size". Sedimentology. 40 (3): 475–512. doi:10.1111/j.1365-3091.1993.tb01347.x.
  14. "Dr. Gregory B. Pasternack – Watershed Hydrology, Geomorphology, and Ecohydraulics :: TFD Hydrometeorology". pasternack.ucdavis.edu. Retrieved 2017-06-12.
  15. Pasternack, Gregory B.; Hinnov, Linda A. (October 2003). "Hydrometeorological controls on water level in a vegetated Chesapeake Bay tidal freshwater delta". Estuarine, Coastal and Shelf Science. 58 (2): 367–387. doi:10.1016/s0272-7714(03)00106-9.
  16. 1 2 Fagherazzi S., 2008, Self-organization of tidal deltas, Proceedings of the National Academy of Sciences, vol. 105 (48): 18692–18695,
  17. 1 2 3 Characteristics of deltas. (Available archived at – checked Dec 2008.)
  18. Bernard Biju-Duval, J. Edwin Swezey. "Sedimentary Geology". Page 183. ISBN   2-7108-0802-1. Editions TECHNIP, 2002. Partial text on Google Books.
  19. 1 2 "Geological and Petrophysical Characterization of the Ferron Sandstone for 3-D Simulation of a Fluvial-deltaic Reservoir". By Thomas C. Chidsey, Thomas C. Chidsey, Jr (ed), Utah Geological Survey, 2002. ISBN   1-55791-668-3. Pages 2–17. Partial text on Google Books.
  20. "Dr. Gregory B. Pasternack – Watershed Hydrology, Geomorphology, and Ecohydraulics :: Tidal Freshwater Deltas". pasternack.ucdavis.edu. Retrieved 2017-06-12.
  21. Pasternack, G. B. 1998. Physical dynamics of tidal freshwater delta evolution. Ph.D. Dissertation. The Johns Hopkins University, 227pp, 5 appendices.
  22. Pasternack, Gregory B.; Hilgartner, William B.; Brush, Grace S. (2000-09-01). "Biogeomorphology of an upper Chesapeake Bay river-mouth tidal freshwater marsh". Wetlands. 20 (3): 520–537. doi:10.1672/0277-5212(2000)020<0520:boaucb>2.0.co;2. ISSN   0277-5212.
  23. Pasternack, Gregory B; Brush, Grace S (2002-03-01). "Biogeomorphic controls on sedimentation and substrate on a vegetated tidal freshwater delta in upper Chesapeake Bay". Geomorphology. 43 (3–4): 293–311. doi:10.1016/s0169-555x(01)00139-8.
  24. Pasternack, Gregory B.; Brush, Grace S. (1998-09-01). "Sedimentation cycles in a river-mouth tidal freshwater marsh". Estuaries. 21 (3): 407–415. doi:10.2307/1352839. ISSN   0160-8347. JSTOR   1352839.
  25. Gottschalk, L. C. (1945). "Effects of soil erosion on navigation in upper Chesapeake Bay". Geographical Review. 35 (2): 219–238. doi:10.2307/211476. JSTOR   211476.
  26. Brush, G. S. (1984). "Patterns of recent sediment accumulation in Chesapeake Bay (Virginia-Maryland, U.S.A.) tributaries". Chemical Geology. 44 (1–3): 227–242. doi:10.1016/0009-2541(84)90074-3.
  27. Orson, R. A.; Simpson, R. L.; Good, R. E. (1992). "The paleoecological development of a late Holocene, tidal freshwater marsh of the upper Delaware River estuary". Estuaries. 15 (2): 130–146. doi:10.2307/1352687. JSTOR   1352687.
  28. D.G.A Whitten, The Penguin Dictionary of Geology (1972)
  29. 1 2 Robert L. Bates, Julia A. Jackson, Dictionary of Geological Terms AGI (1984)
  30. Hori, K. and Saito, Y. Morphology and Sediments of Large River Deltas. Tokyo, Japan: Tokyo Geographical Society, 2003
  31. Maselli, Vittorio; Trincardi, Fabio (2013-05-31). "Man made deltas". Scientific Reports. 3: 1926. doi:10.1038/srep01926. ISSN   2045-2322. PMC   3668317 . PMID   23722597.
  32. "Mineral Photos – Sand and Gravel". Mineral Information Institute. 2011. Archived from the original on 2011-10-06. Retrieved 2011-11-02.
  33. Irwin III, R. et al. 2005. An intense terminal epoch of widespread fluvial activity on early Mars: 2. Increased runoff and paleolake development. Journal of Geophysical Research: 10. E12S15

Bibliography