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Fluvial Geomorphology
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used. Fluvial processes Fluvial processes include the motion of sediment and erosion or deposition on the river bed. The movement of water across the stream bed exerts a shear stress directly onto the bed. If the cohesive strength of the substrate is lower than the shear exerted, or the bed is composed of loose sediment which can be mobilized by such stresses, then the bed will be lowered purely by clearwater flow. In addition, if the river carries significant quantities of sediment, this material can act as tools to enhance wear of the bed ( abrasion). At the same time the fragments themselves are ground down, becoming smaller and more rounded (attrition). Sediment in rivers is transported as either bedload (the coarser frag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Matanuska River 8727 , an impact crater on the minor planet 253 Mathilde
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Matanuska may refer to: *Matanuska Formation, the northern Chugach Mountains, Alaska *Matanuska Glacier, in the Chugach Mountains, Alaska *Matanuska River, in Alaska *Matanuska-Susitna Borough, Alaska, in Alaska *Matanuska-Susitna Valley, in Alaska *Matanuska Valley Colony in Alaska *M/V Matanuska, a vessel in the Alaska Marine Highway System * Matanuska (crater) Matanuska is an impact crater on the minor planet 253 Mathilde. It is in diameter. It is named after a coal field in the Matanuska-Susitna Valley of Alaska; the name was approved by the International Astronomical Union in 2000. References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cohesion (geology)
Cohesion is the component of Shear strength (soil), shear strength of a Rock (geology), rock or soil that is independent of interparticle friction. In soils, true cohesion is caused by following: # Electrostatic forces in stiff consolidation (soil), overconsolidated clays (which may be lost through weathering) # Cementing by Iron, Fe2Oxygen, O3, Calcium, Ca Carbon, CO3, Sodium, Na Chloride, Cl, etc. There can also be apparent cohesion. This is caused by: # Negative capillary pressure (which is lost upon wetting) # Pore pressure response during undrained loading (which is lost through time) # Root cohesion (which may be lost through logging or fire of the contributing plants, or through Solution (chemistry), solution) Typical values of cohesion Cohesion (alternatively called the cohesive strength) is typically measured on the basis of Mohr–Coulomb theory. Some values for rocks and some common soils are listed in the table below. Apparent cohesion of soil During critical state ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mississippi River
The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it flows generally south for to the Mississippi River Delta in the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains all or parts of 32 U.S. states and two Canadian provinces between the Rocky and Appalachian mountains. The main stem is entirely within the United States; the total drainage basin is , of which only about one percent is in Canada. The Mississippi ranks as the thirteenth-largest river by discharge in the world. The river either borders or passes through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana. Native Americans have lived along the Mississippi River and its tributaries for thousands of years. Most were hunter-ga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Delta
A river delta is a landform shaped like a triangle, created by deposition (geology), deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment. It is so named because its triangle shape resembles the Greek letter Delta. 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. 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 Coast, coastline defense and can impact drinking water supply. They are also Ecology, ecologically important, with different species' assemblages ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Floodplain
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudie, A. S., 2004, ''Encyclopedia of Geomorphology'', vol. 1. Routledge, New York. The soils usually consist of clays, silts, sands, and gravels deposited during floods. Because the regular flooding of floodplains can deposit nutrients and water, floodplains frequently have high soil fertility; some important agricultural regions, such as the Mississippi river basin and the Nile, rely heavily on the flood plains. Agricultural regions as well as urban areas have developed near or on floodplains to take advantage of the rich soil and fresh water. However, the risk of flooding has led to increasing efforts to control flooding. Formation Most floodplains are formed by deposition on the inside of river meanders and by overbank flow. Whereve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alluvium
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is typically geologically young and is not consolidated into solid rock. Sediments deposited underwater, in seas, estuaries, lakes, or ponds, are not described as alluvium. Floodplain alluvium can be highly fertile, and supported some of the earliest human civilizations. Definitions The present consensus is that "alluvium" refers to loose sediments of all types deposited by running water in floodplains or in alluvial fans or related landforms. However, the meaning of the term has varied considerably since it was first defined in the French dictionary of Antoine Furetière, posthumously published in 1690. Drawing upon concepts from Roman law, Furetière defined ''alluvion'' (the F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alluvial
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is typically geologically young and is not consolidated into solid rock. Sediments deposited underwater, in seas, estuaries, lakes, or ponds, are not described as alluvium. Floodplain alluvium can be highly fertile, and supported some of the earliest human civilizations. Definitions The present consensus is that "alluvium" refers to loose sediments of all types deposited by running water in floodplains or in alluvial fans or related landforms. However, the meaning of the term has varied considerably since it was first defined in the French dictionary of Antoine Furetière, posthumously published in 1690. Drawing upon concepts from Roman law, Furetière defined ''alluvion'' (the F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hjulström Curve
The Hjulström curve, named after Filip Hjulström (1902–1982), is a graph used by hydrologists and geologists to determine whether a river will erode, transport, or deposit sediment. It was originally published in his doctoral thesis "Studies of the morphological activity of rivers as illustrated by the River Fyris.Hjulstrom, F. (1935). Studies of the morphological activity of rivers as illustrated by the River Fyris, Bulletin. Geological Institute Upsalsa, 25, 221-527." in 1935. The graph takes sediment particle size and water velocity into account.Sediment transportation Last accessed 26 Dec 2011. The upper curve shows the critical erosion velocity in cm/s as a function of particle size in mm, while the lower curve shows the deposition velocity as a function of particle size. Note that the axes are [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into ''static friction'' ("stiction") between non-moving surfaces, and ''kinetic friction'' between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1). *Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. *Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. *Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. *Internal friction is the force resisting motion between the elements making up a so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flow Velocity
In continuum mechanics the flow velocity in fluid dynamics, also macroscopic velocity in statistical mechanics, or drift velocity in electromagnetism, is a vector field used to mathematically describe the motion of a continuum. The length of the flow velocity vector is the flow speed and is a scalar. It is also called velocity field; when evaluated along a line, it is called a velocity profile (as in, e.g., law of the wall). Definition The flow velocity ''u'' of a fluid is a vector field : \mathbf=\mathbf(\mathbf,t), which gives the velocity of an '' element of fluid'' at a position \mathbf\, and time t.\, The flow speed ''q'' is the length of the flow velocity vector :q = \, \mathbf \, and is a scalar field. Uses The flow velocity of a fluid effectively describes everything about the motion of a fluid. Many physical properties of a fluid can be expressed mathematically in terms of the flow velocity. Some common examples follow: Steady flow The flow of a fluid is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suspended Load
The suspended load of a flow of fluid, such as a river, is the portion of its sediment uplifted by the fluid's flow in the process of sediment transportation. It is kept suspended by the fluid's turbulence. The suspended load generally consists of smaller particles, like clay, silt, and fine sands''.'' Sediment transportation The suspended load is one of the three layers of the fluvial sediment transportation system. The bed load consists of the larger sediment which is transported by saltation, rolling, and dragging on the riverbed. The suspended load is the middle layer that consists of the smaller sediment that's suspended. The wash load is uppermost layer which consist of the smallest sediment that can be seen with the naked eye; however, the wash load gets easily mixed with suspended load during transportation due to the very similar process. The wash load never touches the bed even outside of a current. Composition The boundary between bed load and suspended load is not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bedload
The term bed load or bedload describes particles in a flowing fluid (usually water) that are transported along the stream bed. Bed load is complementary to suspended load and wash load. Bed load moves by rolling, sliding, and/or saltating (hopping). Generally, bed load downstream will be smaller and more rounded than bed load upstream (a process known as downstream fining). This is due in part to attrition and abrasion which results from the stones colliding with each other and against the river channel, thus removing the rough texture (rounding) and reducing the size of the particles. However, selective transport of sediments also plays a role in relation to downstream fining: smaller-than average particles are more easily entrained than larger-than average particles, since the shear stress required to entrain a grain is linearly proportional to the diameter of the grain. However, the degree of size selectivity is restricted by the hiding effect described by Parker and Klin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
