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Rivers are an essential component of the terrestrial realm and have been a preferable location for human settlements during history. River is the main expression used for river channels themselves, riparian zones, floodplains and terraces, adjoining uplands dissected by lower channels and river deltas. [3]
When the flow velocity is below 0.1 m/s, the biological community in a river is similar to that in a lake. Usually, in rivers, flow velocity between 0.1–1 m/s is most suitable for major-stream fish species. High flow velocity and turbulence are cues for timing migration and spawning of some fish. Asian carp lay floating eggs when they sense ...
When a species is removed from a river ecosystem the intensity of the effect is related to the connectedness of the species to the food web. [38] An invasive species could be removed with little to no effect, but if important and native primary producers, prey or predatory fish are removed you could have a negative trophic cascade . [ 38 ]
The theory is based on the concept of dynamic equilibrium in which streamforms balance between physical parameters, such as width, depth, velocity, and sediment load, also taking into account biological factors. [2] It offers an introduction to map out biological communities and also an explanation for their sequence in individual sections of ...
However the grains will continue to be transported even if the velocity falls below the entrainment velocity due to the reduced (or removed) friction between the grains and the river bed. Eventually the velocity will fall low enough for the grains to be deposited. This is shown by the Hjulström curve.
The river's discharge at that location depends on the rainfall on the catchment or drainage area and the inflow or outflow of groundwater to or from the area, stream modifications such as dams and irrigation diversions, as well as evaporation and evapotranspiration from the area's land and plant surfaces. In storm hydrology, an important ...
A major effect of river engineering has been a reduced sediment output of large rivers. For example, the Mississippi River produced 400 million tons of sediment per year. [ 22 ] Due to the construction of reservoirs , sediment buildup in man-made levees , and the removal of natural banks replaced with revetments , this sediment output has been ...
Bank erosion is natural, but can be accelerated by humans. Bank erosion is the wearing away of the banks of a stream or river. This is distinguished from erosion of the bed of the watercourse, which is referred to as scour. The roots of trees growing by a stream are undercut by such erosion. As the roots bind the soil tightly, they form ...