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; if buried, they may eventually become sandstone and siltstone through lithification.
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 stream bed or streambed is the channel bottom of a stream or river, the physical confine of the normal water flow. The lateral confines or channel margins are known as the stream banks or river banks, during all but flood stage. Under certain conditions a river can branch from one stream bed to multiple stream beds. A flood occurs when a stream overflows its banks and flows onto its flood plain. As a general rule, the bed is the part of the channel up to the normal water line, and the banks are that part above the normal water line. However, because water flow varies, this differentiation is subject to local interpretation. Usually, the bed is kept clear of terrestrial vegetation, whereas the banks are subjected to water flow only during unusual or perhaps infrequent high water stages and therefore might support vegetation some or much of the time.
Deposition is the geological process in which sediments, soil and rocks are added to a landform or landmass. 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.
The term bed load or bedload describes particles in a flowing fluid that are transported along the stream bed. Bed load is complementary to suspended load and wash load.
Hans Albert Einstein was a Swiss-American engineer and educator, the second child and first son of Albert Einstein and Mileva Marić. Hans A. Einstein was a long-time professor of Hydraulic Engineering at the University of California, Berkeley.
First flush is the initial surface runoff of a rainstorm. During this phase, water pollution entering storm drains in areas with high proportions of impervious surfaces is typically more concentrated compared to the remainder of the storm. Consequently, these high concentrations of urban runoff result in high levels of pollutants discharged from storm sewers to surface waters.
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.
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.
Abrasion is a process of erosion which occurs when material being transported wears away at a surface over time. It is the process of friction caused by scuffing, scratching, wearing down, marring, and rubbing away of materials. The intensity of abrasion depends on the hardness, concentration, velocity and mass of the moving particles. Abrasion generally occurs four ways. Glaciation slowly grinds rocks picked up by ice against rock surfaces. Solid objects transported in river channels make abrasive surface contact with the bed and walls. Objects transported in waves breaking on coastlines cause abrasion. And, finally, abrasion can be caused by wind transporting sand or small stones against surface rocks.
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.
Stream load is a geologic term referring to the solid matter carried by a stream. Erosion and bed shear stress continually remove mineral material from the bed and banks of the stream channel, adding this material to the regular flow of water. The amount of solid load that a stream can carry, or stream capacity, is measured in metric tons per day, passing a given location. Stream capacity is dependent upon the stream's velocity, the amount of water flow, and the gradation.
Stream power originally derived by 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 quantify the energy required to move sediment of a certain size. Stream power is closely related to various other criterion such as stream competency and shear stress. Stream power is a valuable measurement for hydrologists and geomorphologist tackling sediment transport issues as well as for civil engineers using it in the planning and construction of roads, bridges, dams, and culverts.
Acoustic Doppler velocimetry (ADV) is designed to record instantaneous velocity components at a single-point with a relatively high frequency. Measurements are performed by measuring the velocity of particles in a remote sampling volume based upon the Doppler shift effect.
Three components that are included in the load of a river system are the following: dissolved load, wash load and bed material load. The bed material load is the portion of the sediment that is transported by a stream that contains material derived from the bed. Bed material load typically consists of all of the bed load, and the proportion of the suspended load that is represented in the bed sediments. It generally consists of grains coarser than 0.062 mm with the principal source being the channel bed. Its importance lies in that its composition is that of the bed, and the material in transport can therefore be actively interchanged with the bed. For this reason, bed material load exerts a control on river channel morphology. Bed load and wash load together constitute the total load of sediment in a stream. The order in which the three components of load have been considered – dissolved, wash, bed material – can be thought of as progression: of increasingly slower transport velocities, so that the load peak lags further and further behind the flow peak during any event.
A bedrock river is a river that has little to no alluvium mantling the bedrock over which it flows. However, most bedrock rivers are not pure forms; they are a combination of a bedrock channel and an alluvial channel. The way one can distinguish between bedrock rivers and alluvial rivers is through the extent of sediment cover.
In geology, degradation refers to the lowering of a fluvial surface, such as a stream bed or floodplain, through erosional processes. Degradation is the opposite of aggradation. Degradation is characteristic of channel networks in which either bedrock erosion is taking place, or in systems that are sediment-starved and are therefore entraining more material than they are depositing. When a stream degrades, it leaves behind a fluvial terrace. This can be further classified as a strath terrace—a bedrock terrace that may have a thin mantle of alluvium—if the river is incising through bedrock. These terraces may be dated with methods such as cosmogenic radionuclide dating, OSL dating, and paleomagnetic dating to find when a river was at a particular level and how quickly it is downcutting.
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.
In hydrology stream competency, also known as stream competence, is a measure of the maximum size of particles a stream can transport. The particles are made up of grain sizes ranging from large to small and include boulders, rocks, pebbles, sand, silt, and clay. These particles make up the bed load of the stream. Stream competence was originally simplified by the “sixth-power-law,” which states the mass of a particle that can be moved is proportional to the velocity of the river raised to the sixth power. This refers to the stream bed velocity which is difficult to measure or estimate due to the many factors that cause slight variances in stream velocities.
Subhasish Dey is a hydraulician and educator. He is known for his research on the hydrodynamics and acclaimed for his contributions in developing theories and solution methodologies of various problems on hydrodynamics, turbulence, boundary layer, sediment transport and open channel flow. He is currently a Professor of the Department of Civil Engineering, Indian Institute of Technology Kharagpur, where he served as the Head of the Department during 2013-15 and held the position of Brahmaputra Chair Professor during 2009-14 and 2015. He also held the Adjunct Professor position in the Physics and Applied Mathematics Unit at Indian Statistical Institute Kolkata during 2014-19. Besides he has been named a Distinguished Visiting Professor at the Tsinghua University in Beijing, China.
