Stream Channel Characteristics

Waste Systems 

Improvement of Streams – Streamflow starts when water is added to the surface from precipitation, dissolving snow, and groundwater. Waste frameworks form to move water off the land effectively. Streamflow starts as a moving sheet wash, which is a weak surface layer of water. The water descends along the steepest slope and begins to erode the surface by making small rill channels. As the rills bend, develop and cut into channels, more prominent channels materialise. Rapid erosion extends the diverted upslope in a procedure called headward erosion. After some time, nearby channels converge with smaller tributaries joining a more substantial trunk stream. The connected channels become what is known as a waste system. With continuous erosion of the channels, seepage systems change over time. 

Illustration showing stream channel characteristics

Seepage Patterns – Drainages will, in general, occur along zones where rock type and structure are more easily eroded. Therefore, different kinds of seepage patterns occur in an area and these waste examples mirror the structure of the stone. 

Dendritic waste examples are generally standard. They occur on a land surface where the first type of rock provides uniform protection from erosion. 

Outspread seepage patterns create encompassing regions of high geological features where a rise drops from a high focal region to surrounding low regions. 

Rectangular waste examples occur where straight zones of shortcoming, for example, joints or faults, cause the streams to cut down along the weak regions in the stone. 

Trellis waste examples occur where existing rocks separate an area. 

Waste Basins – Each stream in a seepage framework depletes a specific region, called a seepage basin (likewise called a catchment or a watershed). In a separate waste basin, all water falling in the basin channels into a similar stream. A seepage partition isolates a waste basin from other waste basins. Seepage basins can vary in size from a couple of square km, for little streams, to enormous territories, for example, the Mississippi River waste basin, which covers about 40% of the contiguous United States. 

Mainland Divides – Continents can be isolated into enormous waste basins that divide into various sea basins. For instance: North America can be separated into a few basins west of the Rocky Mountains that void into the Pacific Ocean. Streams in the northern part of North America void into the Arctic Ocean, and streams east of the Rocky Mountains void into the Atlantic Ocean or the Gulf of Mexico. Lines isolating these significant seepage basins are named Continental Divides. Such partitions typically run along high mountain peaks that formed so recently that they have not been eroded. Along these lines, primary mainland partitions and the waste examples in the significant basins mirror the ongoing geological history of the landmasses. 

Lasting Streams – Streams that stream all year are called perpetual streams. Their surface is at or underneath the water table. They happen in moist or mild atmospheres where there are adequate precipitation and low dissipation rates. Water levels fluctuate with the seasons, contingent upon the release. 

Ephemeral Streams – Streams that infrequently have water streaming are called ephemeral streams or dry washes. They are below the water table and happen in dry atmospheres with low measures of precipitation and high evaporation rates; they run, for the most part, during flash floods. 

Speed 

A stream’s speed relies upon the position in the stream channel, anomalies in the stream channel brought about by safe stone, and stream angle. Contact eases backwater along channel edges. Contact is more prominent in more extensive, shallower streams and less in smaller, more profound streams. 

In straight channels, the most elevated speed is in the middle. In bent channels, the most extreme speed follows the outside bend where the channel is specially scoured and developed. Within the bend where the speed is lower, the deposition of residue happens. The most profound piece of the channel is known as the thalweg, which meanders with the bend of the stream. Stream around bends follows a winding path.

A stream can be either laminar, in which all water particles travel along in equal ways, or turbulent, in which single particles take unpredictable paths. The stream is naturally violent. This is clamorous and inconsistent, with inexhaustible blending, twirling whirlpools, and occasionally at high speed. The disturbance is brought about by stream blocks and shear in the water. Violent swirls scour the channel bed and can keep dregs in suspension longer than a laminar stream and, in this way, helps erode the stream base. 

Cross-Sectional Shape 

Cross-sectional shapes fluctuate with the position in the stream and release. The most intense part of a channel happens where the stream speed is the most elevated. Both width and intensity increment downstream because of release increments downstream. As release builds, the cross-sectional shape will change, with the stream getting wider and more extensive. 

Erosion by Streams 

Streams erode because they can collect rock particles and transport them to another area. The size of the particles that can be transported relies upon the speed of the stream and whether the stream is laminar or fierce. The violent stream can keep pieces in suspension longer than the laminar stream. 

Streams can likewise erode by undermining their banks, bringing about mass-eroding forms like droops or slides. At the point when the undercut material falls into the stream, the pieces can be moved away by the stream. 

Streams can cut further into their channels if the area is inclined or if there is a regional change in the base level. As they cut further into their channels, the stream evacuates the material that once made up the channel base and sides. 

Albeit moderate, as rocks move along the stream base and slam into each other, abrasion of the stones occurs, making smaller pieces that would then be able to be transported by the stream. 

Eventually, since specific stones and minerals are effortlessly broken down in the water, disintegration happens, causing broken particles to be transported by the stream. 

Dregs Transport and Deposition 

The stone particles and broken particles conveyed by the stream are called the stream’s heap. Stream load is divided into three categories. 

Suspended load – Particles that are conveyed alongside the water in the first part of the streams. The size of these particles depends upon their thickness and the speed of the stream. Higher speed currents can convey bigger and denser particles. 

Bed Load – Denser and coarser particles that stay on the bed of the stream often move by saltation (hopping) because of crashing particles and fierce vortexes. Note that dregs can move between bedload and suspended burden as the speed of the stream changes. 

Broken download – Particles that have been brought into the water by compound enduring rocks. This heap is undetectable because the particles have disintegrated in the water. The disintegrated load comprises mostly of HCO3-2 (bicarbonate particles), Ca+2, SO4-2, Cl-, Na+2, Mg+2, and K+. These particles are ultimately conveyed to the seas and give the seas their salty nature. Streams that have a profound underground source, for the most part, have a higher broken-down burden than those whose source is on the Earth’s surface. 

The most extreme size of particles that can be conveyed as a suspended load by the stream is called the stream skill. The most extreme load conveyed by the stream is called the stream limit—both ability and limit increase with expanding release. At high release, rock and cobble-size material can move with the stream and are transported in this way. At low release, the more significant parts become stranded, and only the smaller, sand, residue, and mud sections move. 

At the point when the stream speed diminishes, the capability is decreased, and the dregs drop out. The water arranges residue in grain sizes. Sand is expelled from the rock, and mud from both. Rock settles in channels. Sand drops out close to channel situations. Sediment and mud cover floodplains from channels. 

Changes Downstream 

As one moves downstream: 

Release increases, as noted above, because water is added to the stream from tributary streams and groundwater. 

As release expands, the width, intensity, and average speed of the stream increases. 

The slope of the stream, in any case, will diminish. 

It might appear to be counter to your perceptions that speed increases in the downstream direction since when one watches a mountain stream close to the headwaters where the slope is high, it seems to have a higher speed than a stream streaming along a gentle angle. Be that as it may, the water in the mountain stream is likely streaming in a dense way, because of the enormous stones and cobbles which make up the streambed. On the off chance that the stream is turbulent, at that point, it takes more time for the water to reach every part of the equivalent straight separation, and along these lines, the average speed is lower.

Additionally, as one moves downstream, the size of particles that constitute the bed load of the stream will result in a general reduction. Even though the speed of the stream increases downstream, the bed load molecule size declines chiefly because the bigger particles are left in the bedload at higher rises and eroded areas of particles will, in general, decrease in size. The arrangement of the particles in the bed load will, in general, change along the stream as various bedrock is eroded and added to the stream’s heap. 

Long Profile 

A plot of height versus separation. Generally, this shows a high inclination or slant close to the source of the stream and a gentle angle as the stream moves toward its mouth. The long profile is inward and upward, as indicated in the diagram below.

Base Level 

The base level is characterized as the constraining level underneath where a stream cannot erode its channel. For streams that emptied into the seas, the base level is at ocean level. Regional base levels can happen where the stream meets a safe collection of rock, where a characteristic or man-made dam obstructs further channel erosion, or where the stream exhausts into a lake. 

At the point when a natural or man-made dam hinders a stream, the stream acclimatises to the new base level by altering its extended profile. In the model above, the long profile above and underneath the dam is balanced. Erosion happens downstream from the dam (mainly if it is a natural dam and water can stream over the top). Only upstream from the dam, the speed of the stream is brought down with the goal that the deposition of dregs happens, leading the slope to become lower. The dam becomes the new base level for the part of the stream upstream from the dam. 

As a rule, if the base level is lowered, the stream descends to its channel and erosion is quickened. On the off chance that the base level is raised, the stream stores silt and straightens out its profile to the new base level. 

Valleys and Canyons 

Land far above base level is liable to downcutting by the stream. Quick downcutting makes an eroded trough, which can turn out to be either a valley or gorge. A valley has gently slanting sidewalls that show a V-shape cross-area. A canyon has soak sidewalls that form precipices. Regardless of whether a valley or gorge, the shape relies upon the rate of erosion and quality of the stones. When all is said in done, slow downcutting and fragile, effectively erodable rocks cause valleys, and quick downcutting in more grounded rocks causes gullies. 

Since geologic procedures stack solid and frail rocks, such stratigraphic variety frequently yields a stepped profile of the ravine dividers, as found in the Grand Canyon. Solid rocks yield vertical bluffs, and fragile rocks produce more gently slanted gorge dividers. 

Dynamic downcutting flushes dregs out of channels. Only after the dregs are flushed, can we facilitate downcutting—valleys store silt when the base level is raised. 

Rapids 

Rapids are hard water with a turbulent surface. Rapids happen when the stream inclination unexpectedly increases, where the stream runs over huge clasts in the base of the stream, or where there is a sudden narrowing of the channel. The abrupt change in slope may happen where a functioning flaw crosses the stream channel. Large clasts might be moved into the stream by a tributary causing rapids where the two streams join. Unexpected narrowing of the stream may occur if the stream experiences solid stone that is not easily eroded. 

Waterfalls 

Waterfalls are transitory base levels brought about by substantial erosion of solid rocks. After arriving at the solid stone, the stream tumbles down the precarious slant in the form of waterfalls. Since the pace of the stream increases on this quick change in slope, erosion occurs at the base of the waterfall where a dive pool occurs. This can start rapid erosion at the base, undermining the bluff that caused the waterfall. When undermining happens, the precipice is subject to rockfalls or slides. These effects in the waterfall withdraw upstream and the stream ultimately dissolves through the bluff to expel the waterfall. 

Niagara Falls in New York is a genuine model. Lake Erie drops 55 m streaming toward Lake Ontario. A dolostone caprock is secure, and the hidden shale erodes—squares of unsupported dolostone break down and fall. 

Niagara Falls persistently erodes south toward Lake Erie. In brief, preoccupation with the water that streams over the American Falls separates uncovered large squares of rock. The pace of the southward retreat of Niagara Falls is directly 0.5 m/yr. Ultimately, the falls will arrive at Lake Erie, and when that happens, Lake Erie will deplete. 

Channel Patterns 

Straight Channels – Straight stream channels are uncommon. Where they do happen, the channel is generally constrained by a direct zone of shortcoming in the first rock, similar to say the lowest or joint framework. 

Indeed, even in straight diverted parts of water streams flow in a bent manner, with the most intense piece of the channel changing from close to one bank to approach the other. Speed is most elevated in the zone overlying the most intense part of the stream. In these regions, the residue is moved promptly, forming pools. Where the speed of the stream is low, dregs remain to shape bars. 

The bank nearest to the zone of most rapid speed is generally eroded and causes a cut bank. 

Meandering Channels – Because of the speed of a stream, and particularly in streams streaming over low slopes with effectively eroded banks, straight channels will inevitably cut into meandering channels. Erosion will occur on the outer edges of the meandering twists, where the speed of the stream is most significant. Silt deposition will happen along with the inward meandering twists where the speed is low. Such deposition of dregs causes open bars, called point bars. Since meandering streams are constantly dissolving on the outer twists and storing dregs along with the inward twists, meandering stream channels will, in general, relocate to and fro over their floodplain. 

If eroding, outwardly wandering twists keep occurring in the long run, a meandering twist can be cut off from the remainder of the stream. When this happens, the cut-off wandering twist, since it is as yet a downturn, will gather water and construct a kind of lake called an oxbow lake. 

Braided Channels – In streams having exceptionally and effectively eroded banks, dregs remain to frame bars and islands that are uncovered during times of low release. In such a stream, the water streams in a braided pattern around the islands and bars, partitioning and rejoining as it streams downstream. Such a channel is named a braided channel. During times of great release, the whole stream channel may contain water, and the islands are secured to become submerged bars. During such high release, a portion of the islands could erode, however, the silt would be resaved as the release diminishes, framing new islands or submerged bars. Islands may become impervious to erosion should they become reduced by vegetation.

Stream Deposits 

Abrupt changes in speed can bring about deposition by streams. Inside a stream, we have seen that the speed differs with the position, and if silt moves at the slower speed of some part of the stream, the residue will leave suspension and remain. Other unexpected changes in speed that influence the entire stream can likewise happen. For instance, if the release is expanded suddenly, as it may be during a flood, the stream will overflow its banks and flow onto the floodplain where the speed will, at that point, abruptly decline. These result in the deposition of high points such as levees and floodplains. If the slope of the stream suddenly changes by exhausting into a level permanent basin, a sea basin, or a lake, the speed of the stream will unexpectedly diminish, bringing about the deposition of residue that can never again be moved. This can bring about the deposition of such landforms as alluvial fans and deltas. 

Floodplains and Levees – As a stream overflows its banks during a flood, the speed of the flood will initially be high. However, it will gradually decline as the water streams out over the gentle inclination of the floodplain. On account of the decline in speed, the coarser-grained suspended dregs will settle along the riverbank, in the long run developing a natural levee. Natural levees furnish some assurance from flooding because with each flood, the levee is fabricated higher, and in this way, the release must be higher for the ensuing flood to happen. (Note that the levees we observe along the Mississippi River here in New Orleans are not regular levees, but man-made levees, built to shield the floodplain from floods. The regular levees do shape the high ground as confirmed by the flooding that happened because of levee ruptures during Hurricane Katrina). 

Terraces- Terraces are uncovered previous floodplain stores that occur when the stream starts downcutting into its flood plain (this is generally brought about by provincial elevation or by bringing down the regional base level, for example, a drop in ocean level). 

Alluvial Fans – When a lofty mountain stream enters a level valley, there is an unexpected decrease in inclination and speed. Dregs carried in the stream will unexpectedly settle along the valley dividers in an alluvial fan. As the speed of the mountain stream eases back, it gathers dregs and separates into various distributary channels. 

Deltas – When a stream enters a stationary waterway, for example, a lake or sea, again, there is an unexpected decrease in speed and the stream stores its dregs in a store called a delta. Deltas assemble outwardly from the coastline. However, they will possibly endure if the sea currents are not sufficiently able to evacuate the silt.

As the speed of a stream diminishes on entering the delta, the stream gets bogged with residue and conditions become conducive to a plaited stream channel, yet instead of twisting, the stream branches into numerous smaller streams called distributary streams. 

In the course of the last 1,000 years, the vast majority of the land that makes up southern Louisiana has been worked by the Mississippi River, saving residue to frame delta flaps. These delta flaps have moved to and fro over time as the River’s course changed because of changes in ocean level and the River attempting to keep up the briefest and steepest way to the Gulf of Mexico.

Read more about Braided Channels

References

Cite/Link to This Article

  • "Stream Channel Characteristics". Geography Revision. Accessed on August 19, 2022. https://geography-revision.co.uk/a-level/physical/stream-channel-characteristics/.

  • "Stream Channel Characteristics". Geography Revision, https://geography-revision.co.uk/a-level/physical/stream-channel-characteristics/. Accessed 19 August, 2022.

  • Stream Channel Characteristics. Geography Revision. Retrieved from https://geography-revision.co.uk/a-level/physical/stream-channel-characteristics/.