Drainage divide - Wikipedia
The correlation between physiographic characteristics of drainage basin to various . initial catchment i.e. from the part of basin divide to discharge zones are .. susceptible to erosion can be divided into the three stages viz. monadnock (old). Alternative Titles: catchment area, catchment basin, watershed The boundary between drainage basins is a drainage divide: all the precipitation on opposite. Stratigraphic and topographic relationships indicate that early erosional erosion of drainage divides and stream capture, overflow of the divides, or headward growth of highly susceptible to this type of modification, which does not occur.
The various morphometric parameters have been correlated with each other to understand their underlying relationship and control over the basin hydrogeomorphology. The result thus generated provides adequate knowledge base required for decision making during strategic planning and delineation of prioritised hazard management zones in mountainous terrains.Drainage system geography for ssc
The form and structure of drainage basins and their associated drainage networks are described by their morphometric parameters. Morphometric properties of a drainage basin are quantitative attributes of the landscape that are derived from the terrain or elevation surface and drainage network within a drainage basin. Application of quantitative techniques in morphometric analysis of drainage basins was initially undertaken by Horton et al.
Remote sensing and Geographical Information System GIS techniques are increasingly being used for morphometric analysis of drainage basins throughout the world [ 9 — 13 ]. Quantitative techniques have been applied to study the morphometric properties of different drainage basins in India [ 14 — 23 ]. Several authors have studied morphometric properties of drainage basins as indicators of structural influence on drainage development and neotectonic activity [ 24 — 27 ].
In many studies morphometric analysis has been used to assess the groundwater potentiality of the basins and to locate suitable sites for construction of check dams and artificial recharge structures [ 28 — 32 ]. Watershed prioritisation based on morphometric characteristics has also been carried out and aids in the mapping of high flood potential and erosion prone zones [ 33 — 37 ].
Drainage basin | geology | yogaua.info
Present study bridges the connection between surface morphometry and subsurface geology of a drainage basin to produce effective information as a part of basin management. So the objective of the present research is to study the morphometric parameters of Supin River basin and to identify the influence of the underlying geology on the morphometric parameters of the basin and finally to generate a substantial knowledge base regarding the relationship between surface morphometry and subsurface lithology for integrated basin management.
The basin covers an area of The study area has three climatic zones: The region receives heavy snowfall between November and March. The rainfall varies from 1, to 1, mm annually. Location map of Supin River basin having an area of Knick points are marked as K.
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- Drainage basin
The basin is underlain by rocks belonging to three main geological formations: Martoli, Vaikrita, and Garhwal.
The upstream portion of the Supin basin, which is mainly drained by its three major tributaries, namely, Har Ki Dun Gad, Borasu Gad, and Ruinsara Gad, is underlain by granite-gneisses and two mica schists belonging to the MCT sheet. The middle portion of the basin is underlain by rocks consisting of Greater Himalayan Gneisses Augen gneisses and porphyritic granites and phyllites, quartzites, and biotite grade schists separated by the Munsiari Thrust MTwhereas near the mouth of the basin, it consists of leucogranite Figure 2 c [ 46 — 48 ].
The generation of depressionless DEM is always the preparatory step for morphometric analysis of drainage basin. Depressions are data errors or result from the averaging involved in assigning elevation values to cells pixels of finite area. These spurious depressions interfere with the correct routing of flow paths during the watershed analysis, especially in areas of low relief.
The Watershed process solves this problem by first locating and filling the depressions. This depressionless DEM is used to compute the flow direction and flow accumulation raster. Further simulation of these two raster produces the standard flow paths and subwatersheds. The Supin River basin has been classified into 27 subwatersheds. Only those watersheds have been considered for this study which includes streams of at least three different orders. Thereafter, 36 morphometric parameters Table 1 have been computed for the entire Supin basin, as well as for each of the subwatersheds.
The morphometric parameters have been evaluated from four different aspects—drainage network, basin geometry, drainage texture, and relief. Streams carry dissolved ions, the products of chemical weathering, into the oceans and thus make the sea salty. Streams are a major part of the erosional process, working in conjunction with weathering and mass wasting.
Much of the surface landscape is controlled by stream erosion, evident to anyone looking out of an airplane window. Streams are a major source of water, waste disposal, and transportation for the world's human population.
Most population centers are located next to streams.
When stream channels fill with water the excess flows onto the the land as a flood. Floods are a common natural disaster. The objectives for this discussion are as follows: How do drainage systems develop and what do they tell us about the geology of an area? How do stream systems operate? How do streams erode the landscape? What kinds of depositional features result from streams?
How do drainage systems evolve? What causes flooding and how can we reduce the damage from floods? Drainage Systems Development of Streams - Steamflow begins when water is added to the surface from rainfall, melting snow,and groundwater.
Drainage systems develop in such a way as to efficiently move water off the land. Streamflow begins as moving sheetwash which is a thin surface layer of water. The water moves down the steepest slope and starts to erode the surface by creating small rill channels. As the rills coalesce, deepen, and downcut into channels larger channels form. Rapid erosion lengthens the channel upslope in a process called headward erosion. Over time, nearby channels merge with smaller tributaries joining a larger trunk stream.
The linked channels become what is known as a drainage network. With continued erosion of the channels, drainage networks change over time. Drainage Patterns - Drainages tend to develop along zones where rock type and structure are most easily eroded. Thus various types of drainage patterns develop in a region and these drainage patterns reflect the structure of the rock. Dendritic drainage patterns are most common. They develop on a land surface where the underlying rock is of uniform resistance to erosion.
Radial drainage patterns develop surrounding areas of high topography where elevation drops from a central high area to surrounding low areas. Rectangular drainage patterns develop where linear zones of weakness, such as joints or faults cause the streams to cut down along the weak areas in the rock.
Trellis drainage patterns develop where registrant rocks break up the landscape see figure Drainage Basins - Each stream in a drainage system drains a certain area, called a drainage basin also called a catchment or a watershed.
In a single drainage basin, all water falling in the basin drains into the same stream. A drainage divide separates each drainage basin from other drainage basins. Continental Divides - Continents can be divided into large drainage basins that empty into different ocean basins.
North America can be divided into several basins west of the Rocky Mountains that empty into the Pacific Ocean. Lines separating these major drainage basins are termed Continental Divides. Such divides usually run along high mountain crests that formed recently enough that they have not been eroded. Thus major continental divides and the drainage patterns in the major basins reflect the recent geologic history of the continents.
Permanent Streams - Streams that flow all year are called permanent streams. Their surface is at or below the water table. They occur in humid or temperate climates where there is sufficient rainfall and low evaporation rates. Water levels rise and fall with the seasons, depending on the discharge. Ephemeral Streams - Streams that only occasionally have water flowing are called ephemeral streams or dry washes. They are above the water table and occur in dry climates with low amounts of rainfall and high evaporation rates.
They flow mostly during rare flash floods. Geometry and Dynamics of Stream Channels Discharge The stream channel is the conduit for water being carried by the stream.
The stream can continually adjust its channel shape and path as the amount of water passing through the channel changes. The volume of water passing any point on a stream is called the discharge. As the amount of water in a stream increases, the stream must adjust its velocity and cross sectional area in order to form a balance. Discharge increases as more water is added through rainfall, tributary streams, or from groundwater seeping into the stream.
As discharge increases, generally width, depth, and velocity of the stream also increase. Velocity A stream's velocity depends on position in the stream channel, irregularities in the stream channel caused by resistant rock, and stream gradient. Friction slows water along channel edges. Friction is greater in wider, shallower streams and less in narrower, deeper streams.
In straight channels, highest velocity is in the center. In curved channels,The maximum velocity traces the outside curve where the channel is preferentially scoured and deepened. On the inside of the curve were the velocity is lower, deposition of sediment occurs. The deepest part of the channel is called the thalweg, which meanders with the curve the of the stream.
Flow around curves follows a spiral path. Stream flow can be either laminar, in which all water molecules travel along similar parallel paths, or turbulent, in which individual particles take irregular paths.
Stream flow is characteristically turbulent. This is chaotic and erratic, with abundant mixing, swirling eddies, and sometimes high velocity. Turbulence is caused by flow obstructions and shear in the water. Turbulent eddies scour the channel bed, and can keep sediment in suspension longer than laminar flow and thus aids in erosion of the stream bottom. Cross Sectional Shape Cross-sectional shape varies with position in the stream, and discharge.
The deepest part of channel occurs where the stream velocity is the highest. Both width and depth increase downstream because discharge increases downstream. As discharge increases the cross sectional shape will change, with the stream becoming deeper and wider. Erosion by Streams Streams erode because they have the ability to pick up rock fragments and transport them to a new location. The size of the fragments that can be transported depends on the velocity of the stream and whether the flow is laminar or turbulent.
Turbulent flow can keep fragments in suspension longer than laminar flow. Streams can also erode by undercutting their banks resulting in mass-wasting processes like slumps or slides. When the undercut material falls into the stream, the fragments can be transported away by the stream. Streams can cut deeper into their channels if the region is uplifted or if there is a local change in base level.
As they cut deeper into their channels the stream removes the material that once made up the channel bottom and sides. Although slow, as rocks move along the stream bottom and collide with one another, abrasion of the rocks occurs, making smaller fragments that can then be transported by the stream. Finally, because some rocks and minerals are easily dissolved in water, dissolution also occurs, resulting in dissolved ions being transported by the stream.
Sediment Transport and Deposition The rock particles and dissolved ions carried by the stream are the called the stream's load. Stream load is divided into three categories. Suspended Load - particles that are carried along with the water in the main part of the streams.
The size of these particles depends on their density and the velocity of the stream.
Higher velocity currents in the stream can carry larger and denser particles. Bed Load - coarser and denser particles that remain on the bed of the stream most of the time but move by a process of saltation jumping as a result of collisions between particles, and turbulent eddies. Note that sediment can move between bed load and suspended load as the velocity of the stream changes. Dissolved Load - ions that have been introduced into the water by chemical weathering of rocks. This load is invisible because the ions are dissolved in the water.
These ions are eventually carried to the oceans and give the oceans their salty character. Streams that have a deep underground source generally have higher dissolved load than those whose source is on the Earth's surface. The maximum size of particles that can be carried as suspended load by the stream is called stream competence. The maximum load carried by the stream is called stream capacity. Both competence and capacity increase with increasing discharge.
At high discharge boulder and cobble size material can move with the stream and are therefore transported. At low discharge the larger fragments become stranded and only the smaller, sand, silt, and clay sized fragments move. When flow velocity decreases the competence is reduced and sediment drops out. Sediment grain sizes are sorted by the water. Sands are removed from gravels; muds from both.
Gravels settle in channels. Sands drop out in near channel environments.
Silts and clays drape floodplains away from channels. Changes Downstream As one moves along a stream in the downstream direction: Discharge increases, as noted above, because water is added to the stream from tributary streams and groundwater. As discharge increases, the width, depth, and average velocity of the stream increase. The gradient of the stream, however, will decrease.
Streams and Drainage Systems
It may seem to be counter to your observations that velocity increases in the downstream direction, since when one observes a mountain stream near the headwaters where the gradient is high, it appears to have a higher velocity than a stream flowing along a gentle gradient.
But, the water in the mountain stream is likely flowing in a turbulent manner, due to the large boulders and cobbles which make up the streambed.
If the flow is turbulent, then it takes longer for the water to travel the same linear distance, and thus the average velocity is lower. Also as one moves in the downstream direction, The size of particles that make up the bed load of the stream tends to decrease.
Even though the velocity of the stream increases downstream, the bed load particle size decreases mainly because the larger particles are left in the bed load at higher elevations and abrasion of particles tends to reduce their size. The composition of the particles in the bed load tends to change along the stream as different bedrock is eroded and added to the stream's load.
Long Profile A plot of elevation versus distance. Usually shows a steep gradient or slope, near the source of the stream and a gentle gradient as the stream approaches its mouth. The long profile is concave upward, as shown by the graph below. Base Level Base level is defined as the limiting level below which a stream cannot erode its channel. For streams that empty into the oceans, base level is sea level.
Local base levels can occur where the stream meets a resistant body of rock, where a natural or artificial dam impedes further channel erosion, or where the stream empties into a lake. When a natural or artificial dam impedes stream flow, the stream adjusts to the new base level by adjusting its long profile. In the example here, the long profile above and below the dam are adjusted. Erosion takes place downstream from the dam especially if it is a natural dam and water can flow over the top.
Just upstream from the dam the velocity of the stream is lowered so that deposition of sediment occurs causing the gradient to become lower. The dam essentially become the new base level for the part of the stream upstream from the dam. In general, if base level is lowered, the stream cuts downward into its channel and erosion is accelerated. If base level is raised, the stream deposits sediment and readjusts its profile to the new base level. Valleys and Canyons Land far above base level is subject to downcutting by the stream.
Rapid downcutting creates an eroded trough which can become either a valley or canyon. A valley has gently sloping sidewalls that show a V-shape in cross-section. A Canyon has steep sidewalls that form cliffs. Whether or valley or canyon is formed depends on the rater of erosion and strength of the rocks. Because geologic processes stack strong and weak rocks, such stratigraphic variation often yields a stair step profile of the canyon walls, as seen in the Grand Canyon.
Strong rocks yield vertical cliffs, whereas weak rocks produce more gently sloped canyon walls. Active downcutting flushes sediment out of channels. Only after the sediment is flushed our can further downcutting occur. Valleys store sediment when base level is raised. Rapids Rapids are turbulent water with a rough surface. Rapids occur where the stream gradient suddenly increases, where the stream flows over large clasts in the bed of the stream, or where there is an abrupt narrowing of the channel.
Sudden change in gradient may occur where an active fault crosses the stream channel. Large clasts may be transported into the stream by a tributary stream resulting in rapids where the two streams join. Abrupt narrowing of the stream may occur if the stream encounters strong rock that is not easily subject to erosion.
Waterfalls Waterfalls are temporary base levels caused by strong erosion resistant rocks. Upon reaching the strong rock, the stream then cascades or free falls down the steep slope to form a waterfalls. Because the rate of flow increases on this rapid change in gradient, erosion occurs at the base of the waterfall where a plunge pool forms. This can initiate rapid erosion at the base, resulting in undercutting of the cliff that caused the waterfall.
When undercutting occurs, the cliff becomes subject to rockfalls or slides. This results in the waterfall retreating upstream and the stream eventually eroding through the cliff to remove the waterfall. Niagara Falls in upstate New York is a good example. Lake Erie drops 55 m flowing toward Lake Ontario. A dolostone caprock is resistant and the underlying shale erodes. Blocks of unsupported dolostone collapse and fall.