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. The soils usually consist of clays, silts, sands, and gravels deposited during floods.
An entrenched river, or entrenched stream is a river or stream that flows in a narrow trench or valley cut into a plain or relatively level upland. Because of lateral erosion streams flowing over gentle slopes over a time develops meandering course. Meanders form where gradient is very gentle, for example in floodplain and delta. Meandering is the feature of the middle and final course of the river. But very deep and wide meanders can also be found cutting hard rocks. Such meanders are called incised or entrenched meanders. The exception is that entrenched meanders are formed during the upliftment of land where river is young. They widen and deepen over time and can be found as deep gorges or canyons in hard rock. In the case of or either an entrenched stream or river, it is often presumed that the watercourse has inherited its course by cutting down into bedrock from a pre-existing plain with little modification of the original course. The down-cutting of the river system could be the result not only of tectonic uplift but also of other factors such as river piracy, decrease of load, increase of runoff, extension of the drainage basin, or change in base level such as a fall in sea level. General, nongeneric terminology for either a river or stream that flows in a narrow trench or valley, for which evidence of a preexisting plain or relatively level upland can be either absent or present is either valley meander or meander valley with the latter term being preferred in literature.
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 English usage, aits or eyots.
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.
A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank and deposits sediments on an inner, convex bank which is typically a point bar. The result of this coupled erosion and sedimentation is the formation of a sinuous course as the channel migrates back and forth across the axis of a floodplain.
The terms river morphology and its synonym stream morphology are used to describe the shapes of river channels and how they change in shape and direction over time. The morphology of a river channel is a function of a number of processes and environmental conditions, including the composition and erodibility of the bed and banks ; erosion comes from the power and consistency of the current, and can effect the formation of the river's path. Also, vegetation and the rate of plant growth; the availability of sediment; the size and composition of the sediment moving through the channel; the rate of sediment transport through the channel and the rate of deposition on the floodplain, banks, bars, and bed; and regional aggradation or degradation due to subsidence or uplift. River morphology can also be affected by human interaction, which is a way the river responds to a new factor in how the river can change its course. An example of human induced change in river morphology is dam construction, which alters the ebb flow of fluvial water and sediment, therefore creating or shrinking estuarine channels. A river regime is a dynamic equilibrium system, which is a way of classifying rivers into different categories. The four categories of river regimes are Sinuous canali- form rivers, Sinuous point bar rivers, Sinuous braided rivers, and Non-sinuous braided rivers.
A riffle is a shallow landform in a flowing channel. Colloquially, it is a shallow place in a river where water flows quickly past rocks. However, in geology a riffle has specific characteristics.
The environmental impact of reservoirs comes under ever-increasing scrutiny as the global demand for water and energy increases and the number and size of reservoirs increases.
Exposed riverine sediments, or ERS, are composed of silt, sand and gravel deposited by streams but exposed as water level falls.
Stream restoration or river restoration, also sometimes referred to as river reclamation, is work conducted to improve the environmental health of a river or stream, in support of biodiversity, recreation, flood management and/or landscape development.
A river is a natural flowing watercourse, usually freshwater stream, flowing on the surface or inside caves towards another waterbody at a lower elevation, such as an ocean, sea, bay, lake, wetland or another river. In some cases, a river flows into the ground or becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as creek, brook and rivulet. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and Northeast England, and "beck" in Northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague.
A log jam is a naturally occurring phenomenon characterized by a dense accumulation of tree trunks and pieces of large wood across a vast section of a river, stream, or lake. Log jams in rivers and streams often span the entirety of the water's surface from bank to bank. Log jams form when trees floating in the water become entangled with other trees floating in the water, or become snagged on rocks, large woody debris, or other objects anchored underwater. They can build up slowly over months or years, or they can happen instantaneously when large numbers of trees are swept into the water after natural disasters. A notable example caused by a natural disaster is the log jam that occurred in Spirit Lake following a landslide triggered by the eruption of Mount St. Helens. Until they are dismantled by natural causes or humans, log jams can grow exponentially as more wood arriving from upstream becomes entangled in the mass. Log jams can persist for many decades, as is the case with the log jam in Spirit Lake.
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.
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.
River channel migration is the geomorphological process that involves the lateral migration of an alluvial river channel across its floodplain. This process is mainly driven by the combination of bank erosion of and point bar deposition over time. When referring to river channel migration, it is typically in reference to meandering streams. In braided streams, channel change is driven by sediment transport.
Channel patterns are found in rivers, streams, and other bodies of water that transport water from one place to another. Systems of branching river channels dissect most of the sub-aerial landscape, each in a valley proportioned to its size. Whether formed by chance or necessity, by headward erosion or downslope convergence, whether inherited or newly formed. Depending on different geological factors such as weathering, erosion, depositional environment, and sediment type, different types of channel patterns can form.
Braid bars, or mid-channel bars, are river landforms typically present in braided river channels. These formations have many names, including medial, longitudinal, crescentic, and transverse bars, as well as the more colloquial sandflat. Braid bars are distinguished from point bars due to their presence in the middle of a flow channel, rather than along a bank of the river channel.
Riparian-zone restoration is the ecological restoration of riparian-zonehabitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies. A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth; the habitats of plant and animal communities along the margins and river banks are called riparian vegetation, characterized by Aquatic plants and animals that favor them. Riparian zones are significant in ecology, environmental management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grassland, woodland, wetland or sub-surface features such as water tables. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, or riparian strip are used to characterize a riparian zone.
A meander cutoff is a natural form of a cutting or cut in a river occurs when a pronounced meander (hook) in a river is breached by a flow that connects the two closest parts of the hook to form a new channel, a full loop. The steeper drop in gradient (slope) causes the river flow gradually to abandon the meander which will silt up with sediment from deposition. Cutoffs are a natural part of the evolution of a meandering river. Rivers form meanders as they flow laterally downstream, see sinuosity.
Legacy sediment (LS) is depositional bodies of sediment inherited from the increase of human activities since the Neolithic. These include a broad range of land use and land cover changes, such as agricultural clearance, lumbering and clearance of native vegetation, mining, road building, urbanization, as well as alterations brought to river systems in the form of dams and other engineering structures meant to control and regulate natural fluvial processes (erosion, deposition, lateral migration, meandering). The concept of LS is used in geomorphology, ecology, as well as in water quality and toxicological studies.
