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Gravel Bar
A bar in a river is an elevated region of sediment (such as sand or gravel) that has been deposited by the flow. Types of bars include mid-channel bars (also called braid bars and common in braided rivers), point bars (common in meandering rivers), and mouth bars (common in river deltas). 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. Mid-channel bars A mid-channel bar is also often referred to as a braid bar because they are often found in braided river channels. Braided river channels are broad and shallow and found in areas where sediment is easily eroded like at a glacial outwash, or at a mountain front with high sediment loads. These types of river systems are associated with high slope, sediment supply, stream power, shear stress, and bed load transport rates. Braided rivers have complex and unpredictab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravel
Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gravel is classified by grain size, particle size range and includes size classes from granule (geology), granule- to boulder-sized fragments. In the grain size, Udden-Wentworth scale gravel is categorized into granular gravel () and pebble gravel (). ISO 14688 grades gravels as fine, medium, and coarse, with ranges for fine and for coarse. One cubic metre of gravel typically weighs about , or one cubic yard weighs about . Gravel is an important commercial product, with a number of applications. Almost half of all gravel production is used as construction aggregate, aggregate for concrete. Much of the rest is used for road construction, either in the road base or as the road surface (with or without bitumen, asphalt or other binders.) Natu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stream Power
Stream power, originally derived by Ralph Bagnold, R. A. Bagnold in the 1960s, is the amount of energy the water in a river or stream is exerting on the sides and bottom of the river. Stream power is the result of multiplying the density of the water, the acceleration of the water due to gravity, the volume of water flowing through the river, and the slope of that water. There are many forms of the stream power formula with varying utilities, such as comparing rivers of various widths or quantifying the energy required to move sediment of a certain size. Stream power is closely related to other criteria such as stream competency and shear stress. Stream power is a valuable measurement for Hydrology, hydrologists and Geomorphology, geomorphologists tackling sediment transport issues as well as for Civil engineering, civil engineers, who use it in the planning and construction of roads, bridges, dams, and culverts. History Although many authors had suggested the use of power formul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bed Load
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 Saltation (geology), 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 Wear, attrition and Abrasion (geology), abrasion which results from the stones colliding with each other and against the river channel, thus removing the rough texture (Rounding (sediment), 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 Entrainment (physical geography), entrained than larger-than average particles, since the shear stress required to entrain a grain is linearly proportional to the diameter of the grain. Howev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cut Bank
A cut bank, also known as a river cliff or river-cut cliff, is the outside bank of a curve (meander) in a water channel (stream), which is continually undergoing erosion.Essentials of Geology, 3rd Ed, Stephen Marshak Cut banks are found in abundance along mature or meandering streams, they are located opposite the '' slip-off slope'' on the inside of the stream meander. They are shaped much like a small cliff, and are formed as the stream collides with the river bank. It is the opposite of a point bar, which is an area of deposition of material eroded upstream in a cut bank. Typically, cut banks are steep and may be nearly vertical. Often, particularly during periods of high rainfall and higher-than average water levels, trees and poorly placed buildings can fall into the stream due to mass wasting events. Given enough time, the combination of erosion along cut banks and deposition along point bars can lead to the formation of an oxbow lake. Not only are cut banks steep and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dubuque, Iowa
Dubuque (, ) is a city in Dubuque County, Iowa, United States, and its county seat. The population was 59,667 at the 2020 United States census. The city lies along the Mississippi River at the junction of Iowa, Illinois, and Wisconsin, a region locally known as the Tri-State Area. It serves as the main commercial, industrial, educational, and cultural center for the area. Geographically, it is part of the Driftless Area, a portion of North America that escaped all three phases of the Wisconsin Glaciation, resulting in a hilly topography unlike most of the Midwestern United States. Dubuque is a regional tourist destination featuring the city's unique architecture, casinos, and riverside location. It is home to five institutions of higher education. While Dubuque has historically been a center of manufacturing, the local economy also includes health care, publishing, and financial service sectors. History Spain gained control of the Louisiana Territory west of the Mississippi R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thalweg
In geography, hydrography, and fluvial geomorphology, a thalweg or talweg () is the line or curve of lowest elevation within a valley or watercourse. Normally only the horizontal position of the curve is considered (as viewed on a map); the corresponding vertical position is represented in a '' stream profile''. Under international law, a thalweg is instead taken to be the middle of the primary navigable channel of a waterway which is the default legal presumption for the boundary between entities such as states. Thalwegs can have local proprietorial and administrative significance because their formerly somewhat shifting position, reliant on renewed soundings, now more fixed as described internationally, is part of centuries-old custom and practice in some jurisdictions. In some jurisdictions and between some states the median line (between banks) is the preferred boundary presumption as may extend from estuaries. Also being easy to map, drawing "turning points" are the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Streams
A stream is a continuous body of surface water flowing within the bed and banks of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long, large streams are usually called rivers, while smaller, less voluminous and more intermittent streams are known, amongst others, as brook, creek, rivulet, rill, run, tributary, feeder, freshet, narrow river, and streamlet. The flow of a stream is controlled by three inputs – surface runoff (from precipitation or meltwater), daylighted subterranean water, and surfaced groundwater (spring water). The surface and subterranean water are highly variable between periods of rainfall. Groundwater, on the other hand, has a relatively constant input and is controlled more by long-term patterns of precipitation. The stream encompasses surface, subsurface and groundwater fluxes that respond to geological, geomorphological, hydrological and biotic controls. ... [...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. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrology), 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 of regular flooding, floodplains frequently have high soil fertility since nutrients are deposited with the flood waters. This can encourage farming; some important agricultural regions, such as the Nile and Mississippi Basin, Mississippi Drainage basin, river basins, heavily exploit floodplains. Agricultural and urban regions have developed near or on floodplains to take advantage of the rich soil and freshwater. However, the Flood risk, risk of inundation has led to increasing efforts to Flood control, control flooding. Formation Most floodplai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bank (river)
In geography, a bank is the land alongside a body of water. Different structures are referred to as ''banks'' in different fields of geography. In limnology (the study of inland waters), a stream bank or river bank is the terrain alongside the bed of a river, creek, or stream. The bank consists of the sides of the channel, between which the flow is confined. Stream banks are of particular interest in fluvial geography, which studies the processes associated with rivers and streams and the deposits and landforms created by them. Bankfull discharge is a discharge great enough to fill the channel and overtop the banks. The descriptive terms ''left bank'' and ''right bank'' refer to the perspective of an observer looking downstream; a well-known example of this being the southern left bank and the northern right bank of the river Seine defining parts of Paris. The shoreline of ponds, swamps, estuaries, reservoirs, or lakes are also of interest in limnology and are somet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Island
An island or isle is a piece of land, distinct from a continent, completely surrounded by water. There are continental islands, which were formed by being split from a continent by plate tectonics, and oceanic islands, which have never been part of a continent. Oceanic islands can be formed from volcano, volcanic activity, grow into atolls from coral reefs, and form from sediment along shorelines, creating barrier islands. River islands can also form from sediment and debris in rivers. Artificial islands are those made by humans, including small rocky outcroppings built out of lagoons and large-scale land reclamation projects used for development. Islands are host to diverse plant and animal life. Oceanic islands have the sea as a natural barrier to the introduction of new species, causing the species that do reach the island to evolve in isolation. Continental islands share animal and plant life with the continent they split from. Depending on how long ago the continental is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Divergence
In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the rate that the vector field alters the volume in an infinitesimal neighborhood of each point. (In 2D this "volume" refers to area.) More precisely, the divergence at a point is the rate that the flow of the vector field modifies a volume about the point ''in the limit'', as a small volume shrinks down to the point. As an example, consider air as it is heated or cooled. The velocity of the air at each point defines a vector field. While air is heated in a region, it expands in all directions, and thus the velocity field points outward from that region. The divergence of the velocity field in that region would thus have a positive value. While the air is cooled and thus contracting, the divergence of the velocity has a negative value. Physical interpretation of divergence In physical terms, the divergence of a vector field is the extent to which the vector fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
