how does a river choose its course

A river changes with increasing distance downstream from its source towards its mouth. It moves through its upper course, to its mid-course and finally into its lower course. Steep valley sides are typical of a river's upper course in upland areas. The valley here has steep sides and the valley bottom is narrow.

Full Answer

Why do rivers become wide towards the lower part of course?

The water flows at a slow speed, it cannot very much erode the bed nor can it transport much material. But as the volume of water is more, the banks are eroded and the river becomes wide. Towards the lower part of the plain course, the slope of the river bed becomes still less. The speed of the current also decreases.

How is the upper course of a river formed?

The upper course of a river is often in steep, mountain areas. This section of a river is cold, clear and fast-flowing. It has a very steep slope. When the river flows down through the upper course the river channel becomes narrow. This creates vertical erosion forming a V-shaped valley.

How many courses does a river have?

If we look into the whole length of a river we will notice that it has three definite courses: 1. The Upper or Mountain Course 2. The Middle or Plain Course 3. The Lower or Deltaic Course.

What is the middle course of a river?

The Middle Course: As a river leaves the hilly area and enters into a plain, its middle course starts. The slope of the river bed is less on a plain. Hence, the speed of the current is also less, compared to the upper course. The river is fed by many tributaries and its volume of water increases.

How does a river flow?

What is a river?

What is the watershed of a river?

Why is it so hard to measure the length of a river?

What happens when a river tears away rocks and soil?

Why are rivers important?

Which is the largest river in Africa?

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How is the course of a river determined?

Topography plays a major role in determining a river's course. Water will always seek the path of least resistance. It will go around or under rather than up and over whenever possible.

How do rivers change their path?

Abrasion, hydraulic action, and solution are all the ways in which a river erodes the bank and river bed through friction between water, soil, rocks, and other natural material.

What does the course of a river mean?

COURSE OF RIVER Definition & Legal Meaning The course of a river is a line parallel with its banks; the term is not synonymous with the “current” of the river.

Why does it take to get a river to change course or curve?

0:212:56Why Do Rivers Curve? - YouTubeYouTubeStart of suggested clipEnd of suggested clipWater rushes into the newly formed hollow sweeping away loose dirt. And making the hollow evenMoreWater rushes into the newly formed hollow sweeping away loose dirt. And making the hollow even hollow er which lets the water rush a little faster.

How do rivers never stop flowing?

Why do rivers continue to flow, even when little or no rain has fallen? Much of the water feeding a stream runs slowly underground through shallow aquifers. These sediments are saturated like natural sponges and respond slowly to rainfall and drought.

Why are rivers not straight?

It's actually small disturbances in topography that set off chain reactions that alter the path of a river. Any kind of weakening of the sediment on one side of a river due to animal activity, soil erosion, or human activity can draw the motion of the water towards that side.

How many courses are in river?

threeIf we look into the whole length of a river we will notice that it has three definite courses: 1. The Upper or Mountain Course 2. The Middle or Plain Course 3. The Lower or Deltaic Course.

How many courses has a river?

three differentRiver Systems. The river has three different "courses", the Upper Course, Middle Course and Lower Course, each with their own different characteristics. waterfalls, interlocking spurs. meanders, floodplains.

Why is the course of a river divided into three parts?

Rivers are split up into three parts: the upper course, the middle course, and the lower course. The upper course is closest to the source of a river. The land is usually high and mountainous, and the river has a steep gradient with fast-flowing water. There is a lot of vertical erosion and weathering.

Why are rivers zigzag?

If one bank of a river is disturbed and begins to crumble, water fills the hole and sweeps away loose dirt. Over time, this creates a bigger and bigger hole in the river bank. As the water begins to rush faster through the new opening, it slows on the opposite river bank.

Why do rivers flow south?

Most rivers in the world flow downhill, often South, due to gravity. The Nile River is an exception to this rule, flowing from South to North. Other rivers have the ability to flow different directions due to where sloping occurs away from their headwaters.

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What Are the Physical Characteristics of a River?

A river is characterized by continuously flowing water from an upland source into lakes, wetlands or the sea. Rivers are fed by tributary streams or springs, and they include a river channel, shoreline and a floodplain.

What Is the Definition of a River System? - Reference.com

Tony Wheeler/Lonely Planet Images/Getty Images. A river system is a way of describing the larger networks of streams, lakes and rivers that are part of a larger river’s network of tributaries and distributaries; for example, multiple rivers, including the Ohio, Red and Missouri rivers empty into the Mississippi River, serving as tributaries and are part of the Mississippi River’s system.

What is the middle course of a river?

The middle or valley course – In this part of the course, the lateral corassion overtakes the vertical corrasion. The banks continuously get eroded and widen the valley to form the V-shaped valley. The confluence of tributaries in this region increases the volume of water which increases the load of the river. Some deposition of material also occur in this region but transportation is still the main event in this region. The interlocking spurs are formed on both sides of the valley. Rainwash, landslides, soil creep and gullying eventually widen the valley.

What is the role of deposition in river formation?

In this region, deposition plays a chief role in the formation of river beds and extensive flood plains. The volume of water increase due to the joining of many tributaries to the mainstream. The heavy material is dropped and the finer material is carried to the mouth of the river. The deposited material makes the river to get distributed in several small channels forming braid like structure.

How are gorges formed?

The main action of the river is done by vertical corassion. Consequently, a narrow, deep and unique V-shaped valley is formed. Lateral corrasion gets overpowered by the pace of downward lateral cutting and hence do not play an important part. The formation of gorges occurs where the rocks are too hard and resistant. Example – the gorge formed by Indus river in Kashmir. In arid regions, where the rainfall is very low, the narrow deep valleys are formed called canyons. For example – The Bryce Canyon, Utah, U.S.A.

What happens when a rock is dissolved in water?

Corrosion or solution – When soluble or partly soluble rocks come in the contact of water, it gets dissolved by the chemical action and is carried away with water in the form of solution. The best example of these kinds of rocks is limestone rocks which contains calcium carbonate and get easily dissolved and are moved with the water. The splashed water enters the crevices and cracks which makes way for the disintegration of the rocks. Also, the softer rocks are broken down easily when water comes in the contact of these rocks. By this process, the loose fragments of both bed and bank get carried away with water.

Why is the movement of boulders seen during floods?

If you double the velocity of the river, the transporting power increases at least tenfold which is why the movement of even large boulders is seen during floods. Also, the movement of the seasonal rivers is intermittent. It does not remain equally active at all year round. It is most active during the rainy season.

How much water is being carried off by running water?

According to estimates, for every square kilometre of the earth surface, around 200 tons of material in the form of a suspension and 50 tons in form of the solution are being carried off by running water every year. Half of the area of the U.S.A is drained by Mississippi River, takes away more than two million tons of eroded material into the Gulf of Mexico daily. This leads to the lowering of river basins. River Irrawaddy that is located in Myanmar lowers its drainage basin by about 0.5 meters in every 400 years.

Why does the river look muddy?

During floods, the material carried by river doubles which is why the colour of the river looks muddy during a flood.

How does a river flow?

From its source, a river flows downhill as a small stream. Precipitation and groundwater add to the river’s flow. It is also fed by other streams, called tributaries. For instance, the Amazon River receives water from more than 1,000 tributaries.

What is a river?

A river is a large, natural stream of flowing water. Rivers are found on every continent and on nearly every kind of land. Some flow all year round. Others flow seasonally or during wet years. A river may be only kilometers long, or it may span much of a continent. The longest rivers in the world are the Nile in Africa and ...

What is the watershed of a river?

A river’s watershed includes the river, all its tributaries, and any groundwater resources in the area. The end of a river is its mouth. Here, the river empties into another body of water—a larger river, a lake, or the ocean. Many of the largest rivers empty into the ocean.

Why is it so hard to measure the length of a river?

For centuries, scientists have debated which river is longer. Measuring a river is difficult because it is hard to pinpoint its exact beginning and end. Also, the length of rivers can change as they meander, are dam med, or their deltas grow and recede.

What happens when a river tears away rocks and soil?

Little by little, a river tears away rocks and soil along its bed, and carries them downstream. The river carves a narrow, V-shaped valley. Rapids and waterfall s are common to rivers, particularly near their sources. Eventually, the river flows to lower land.

Why are rivers important?

Rivers are important for many reasons. One of the most important things they do is carry large quantities of water from the land to the ocean. There, seawater constantly evaporate s. The resulting water vapor forms clouds. Cloud s carry moisture over land and release it as precipitation. This freshwater feeds rivers and smaller streams. The movement of water between land, ocean, and air is called the water cycle. The water cycle constantly replenish es Earth’s supply of freshwater, which is essential for almost all living things.

Which is the largest river in Africa?

Africa’s two largest rivers are the Nile and the Congo.

What are the three courses of a river?

Article shared by : ADVERTISEMENTS: If we look into the whole length of a river we will notice that it has three definite courses: 1. The Upper or Mountain Course 2. The Middle or Plain Course 3. The Lower or Deltaic Course. 1. The Upper Course: In the mountainous course, a river passes through a steep slope.

What are the main activities of a river in the upper course?

Erosion and transportation are the main activities of a river in the upper course. A river has a deep and narrow channel in this stage. Moreover, some of the rocks over which a river flows are very hard, while the others are soft. As a result of this, the river course is not smooth.

What is the name of the type of erosion that occurs in the upper course of a river?

As a result, the source of the river retreats. This type of erosion of the river is called Headword Erosion. The sources of Sutlej and Koshi have retreated towards Tibetan side and of Kaveri towards west in western ghats. The other two important formations of the upper course of a river are—rapids and waterfalls.

What are the main activities of a mountainous river?

Under such a condition the water can dig the river bed very deeply and carries or pools down heavy boulders and pebbles. Erosion and transportation are the main activities of a river in the upper course.

What is the name of the channel that changes its course very often and becomes winding?

It can hardly erode and transport at this stage. The additional sediments carried by the river during the floods are deposited in this part. The channel is sometimes blocked, the river changes its course very often and becomes winding. Such a winding channel is known as a meander.

What are the two main formations of the upper course of a river?

The other two important formations of the upper course of a river are—rapids and waterfalls . When water flows with high speed over the hard rock surface it is called rapids and when the water falls vertically downward it is called waterfalls .

What is the name of the formation that flows through the river?

In that situation the two sides of the river become so steep that they become almost vertical. The formation is known as Gorge. There are many gorges on the upper course of the Brahmaputra, the Indus, and the Ganges.

What is the upper course of a river?

The upper course of a river is often in steep, mountain areas. This section of a river is cold, clear and fast-flowing. It has a very steep slope. When the river flows down through the upper course the river channel becomes narrow.

What are the functions of rivers?

They provide a home, drinking water, and/ or a hunting ground for many organisms. Furthermore, rivers provide drinking water, irrigation water, transportation, hydro-electrical power, drainage, food, and recreation opportunities. In this lesson we are going to learn about the courses of a river and their wild life.

Where do rivers end?

Rivers flow down to the sea and end there. Many plant and animals live in or near rivers.

What is the winding lowland part of a river?

This winding lowland parts of a river contain muddy, slightly warmer water, which flows more slowly. Plants grow in the bed of the river and at its edges. It also contains a deposition. Large meanders, large flood plains as well as oxbow lakes can be formed at this stage.

What is river landscape?

River Landscape. Rivers are flowing bodies of waters. There are rivers on every continent (except Antarctica). A river basically, has three parts. We call them the courses of a river. This lesson on river landscape (also called riverscape) explains to you about these courses or stages of a river and their wildlife.

What type of erosion creates a V-shaped valley?

This creates vertical erosion forming a V-shaped valley. Waterfalls are also, usually formed at this stage. Rivers with steep slopes form valleys with steep walls and a bottom. Valleys formed by shallower slopes may be broader and gentler.

Why is the volume of water in a river at its greatest in the lower course?

The volume of water in a river is at its greatest in the lower course. This is due to the contribution of water from tributaries. The river channel is deep and wide and the land around the river is flat. Energy in the river is at its lowest and deposition occurs.

When a river floods more substantial material and the majority of deposition occurs next to the river channel?

When a river floods more substantial material and the majority of deposition occurs next to the river channel as the result of increased friction (with the flood plain ). The velocity of the river slows and therefore rapidly reduce its ability to transport material. This leaves a ridge of higher material next to the river channel on both banks of the river known as a levee.

What is the name of the body of water that is found at the mouth of a river?

Estuary . An estuary is a wide, sheltered body of water found at a river’s mouth where it broadens into the sea. It is a combination of salt water from the sea and fresh water from a river. As the river meets the sea at high tide, it slows the flow of water leading to deposition. Mudflats and saltmarsh form in these areas.

What is the area over which rivers flood?

Rivers flood on a regular basis. The area over which they flood is known as the floodplain, and this often coincides with regions where meanders form. Meanders support the formation of floodplains through lateral (sideways) erosion. When rivers flood the velocity of water slows.

What is the path a river takes?

The path that a river takes in its journey over Earth's surface is a bit like the life a human leads between birth and death but, where a human's life is spread out in time, a river's spreads out in geographical space.

How do rivers form?

In warmer places, rivers typically form when water drains from a whole series of upland slopes known as a basin. Water drains from each slope to form a small trickle called a rill.

Why do rivers matter to people?

Photo: Villagers gather on the banks of a river in Bangladesh waiting for humanitarian aid. Photo by Anthony J. DeCapite courtesy of US Marine Corps and US Navy.

How does gravity affect river flow?

Rivers gradually slow down because the water has to overcome friction as it flows —friction as the moving water rubs against the banks and bottom of the river channel itself and friction as layers of water flow past one another. The rate at which a river flows is also affected by the climate and the seasons. Some smaller streams (known as winterbornes ) dry up entirely in summer. Humans also have a huge effect on river flows through abstraction (removing water for many different uses), from irrigation (watering crops in the countryside) to supplying factories and homes with the water they need.

Why do rivers slow down?

Rivers gradually slow down because the water has to overcome friction as it flows—friction as the moving water rubs against the banks and bottom of the river channel itself and friction as layers of water flow past one another. The rate at which a river flows is also affected by the climate and the seasons.

Why do rivers enthrall us?

W hy do rivers enthrall us? Maybe it's because they're teeming with life —everything from nibbling midges to flashing kingfishers and trout and salmon wiggling beneath the ripples. Perhaps it's because water is so central to our existence and so vital to life. Possibly it's to do with the tranquility of a river; in countryside or in cities, the sight of water has an instantly calming effect. All these things come to mind, instinctively or very consciously, whenever we think of rivers or spend time near them swimming, fishing, boating, or canoeing. Let's take a look at what makes rivers so amazing!

Why is sand and gravel bad for rivers?

Removing sand and gravel from river beds for building materials can damage them, for example, while pouring untreated sewage and other wastewater into rivers causes pollution, lowers water quality, and reduces how much life they can support. Thankfully, many people recognize just how important rivers are.

What are the differences between the surface and the bottom of a river?

Temperature differences can be significant between the surface and the bottom of deep, slow-moving rivers. Climate, shading and elevation all affect water temperature. Species living in these environments are called poikilotherms – their internal temperature varies to suit their environmental conditions.

What is the ecology of a river?

The ecology of the river refers to the relationships that living organisms have with each other and with their environment – the ecosystem. An ecosystem is the sum of interactions between plants, animals and microorganisms and between them and non-living physical and chemical components in a particular natural environment.

How does water flow affect the shape of riverbeds?

Flow can be affected by sudden water input from snowmelt, rain and groundwater. Water flow can alter the shape of riverbeds through erosion and sedimentation, creating a variety of changing habitats. The Waikato River is a lotic system.

What is the substrate of a river?

Substrate. The substrate is the surface on which the river organisms live. It may be inorganic, consisting of geological material from the catchment area such as boulders, pebbles, gravel, sand or silt, or it may be organic, including fine particles, leaves, wood, moss and plants.

What is the main factor that makes river ecology different from other water ecosystems?

Water flow is the main factor that makes river ecology different from other water ecosystems. This is known as a lotic (flowing water) system. The strength of water flow varies from torrential rapids to slow backwaters. The speed of water also varies and is subject to chaotic turbulence.

How do fish live in a river?

The ability of fish to live in a river system depends on their speed and duration of that speed – it takes enormous energy to swim against a current. This ability varies and is related to the area of habitat the fish may occupy in the river. Most fish tend to remain close to the bottom, the banks or behind obstacles, swimming in the current only to feed or change location. Some species never go into the current. Most river systems are typically connected to other lotic systems (springs, wetlands, waterways, streams, oceans), and many fish have life cycles that require stages in other systems. Eels, for example, move between freshwater and saltwater. Fish are important consumers and prey species.

How is water chemistry determined?

It is often determined by inputs from the surrounding environment or catchment area but can also be influenced by rain and the addition of pollution from human sources.

How does a river flow?

From its source, a river flows downhill as a small stream. Precipitation and groundwater add to the river’s flow. It is also fed by other streams, called tributaries. For instance, the Amazon River receives water from more than 1,000 tributaries.

What is a river?

A river is a large, natural stream of flowing water. Rivers are found on every continent and on nearly every kind of land. Some flow all year round. Others flow seasonally or during wet years. A river may be only kilometers long, or it may span much of a continent. The longest rivers in the world are the Nile in Africa and ...

What is the watershed of a river?

A river’s watershed includes the river, all its tributaries, and any groundwater resources in the area. The end of a river is its mouth. Here, the river empties into another body of water—a larger river, a lake, or the ocean. Many of the largest rivers empty into the ocean.

Why is it so hard to measure the length of a river?

For centuries, scientists have debated which river is longer. Measuring a river is difficult because it is hard to pinpoint its exact beginning and end. Also, the length of rivers can change as they meander, are dam med, or their deltas grow and recede.

What happens when a river tears away rocks and soil?

Little by little, a river tears away rocks and soil along its bed, and carries them downstream. The river carves a narrow, V-shaped valley. Rapids and waterfall s are common to rivers, particularly near their sources. Eventually, the river flows to lower land.

Why are rivers important?

Rivers are important for many reasons. One of the most important things they do is carry large quantities of water from the land to the ocean. There, seawater constantly evaporate s. The resulting water vapor forms clouds. Cloud s carry moisture over land and release it as precipitation. This freshwater feeds rivers and smaller streams. The movement of water between land, ocean, and air is called the water cycle. The water cycle constantly replenish es Earth’s supply of freshwater, which is essential for almost all living things.

Which is the largest river in Africa?

Africa’s two largest rivers are the Nile and the Congo.