Gcse Core Geography Wjec A (Rivers)

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GSCE GEOGRAPHY CORE: RIVERS

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1) What is the water cycle?

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Seas and oceans contain 97% of the world's water, and ice holds 2%. That leaves just 1% of the world's water as fresh water on land or in the air. This water is recycled again and again through the process of evaporation, condensation and water transfers such as surface run-off.

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Definitions:

1) drainage basin

2) catchment area

3) watershed

4) source

5) confluence

6) tributary

7) Mouth

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1) The area of land drained by a river. 2) The area within the drainage basin.3) The edge of highland surrounding a drainage basin. It marks the boundary between two drainage basins.4) The beginning or start of a river.5) The point at which two rivers or streams join.6) A stream or smaller river which joins a larger stream or river.7) The point where the river comes to the end, usually when entering a sea.

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1) Explain what a long profile of a river is.

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1) Source of river often in an upland area. Near source, a river flows over steep slopes with an uneven surface. (flow over waterfalls and rapids) Highland areas, usually composed of hard igneous rocks.

As river flows down steep slopes the water performs vertical erosion. This form of erosion cuts down towards the river bed and carves out steep-sided V-shaped valleys. As the river flows towards the mouth, the slopes become less steep. Eventually the river will flow over flat land as it approaches the sea. The discharge (amount of water flowing) will increase as the river approaches the sea.

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1) Explain what a cross section of a river profile is.

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Near source of river there is more vertical erosion as river flows downhill, using energy to overcome friction. As a result the channels are narrow and shallow and may contain large boulders and angular fragments eroded and weathered from the steep valley sides. The sediment in the river creates turbulence and friction.

As the river approaches the mouth, velocity and energy increase due to increased discharge. The river performs more lateral erosion making the channel wider, and smoother. As a result there is less turbulence and friction, making the flow of water more efficient.

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1) what is erosion?

2) name and define the four main types of erosion

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1)Erosion is the wearing away of rock and soil found along the river bed and banks. Erosion also involves the breaking down of the rock particles being carried downstream by the river.

2) Hydraulic action is the force of the river against banks can cause air to be trapped in cracks. The pressure weakens the banks and gradually wears it away. - Abrasion is when rocks are carried along by the river wear down the river bed and banks. - Attrition is rocks being carried by the river smash together and break into smaller, smoother and rounder particles. - Solution is soluble particles are dissolved into the river.

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1) what is river transport?

2) name and define the four main types of river transport

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1) Rivers pick up and carry material as they flow downstream

2)Solution is minerals are dissolved in the water and carried along in solution. - Suspension is when fine light materials are carried along in the water. - Saltation is small pebbles and stones are bounced along the river bed. - Traction is large boulders and rocks are rolled along the river bed.

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1) Explain how the levels of energy in a river can effect the transportation process

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1) A Rivers need energy to transport material, and levels of energy change as the river moves from source to mouth. When energy levels are very high, large rocks and boulders can be transported. Energy levels are usually higher near a river's source, when its course is steep and its valley narrow. Energy levels rise even higher in times of flood. When energy levels are low, only small particles can be transported (if any). Energy levels are lowest when velocity drops as a river enters a lake or sea (at the mouth).

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1) what is decomposition in a river?

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1) It's when a river loses energy, it will drop or deposit some of the material it is carrying. It may take place when a river enters an area of shallow water or when the volume of water decreases - for example, after a flood or during times of drought. It is common towards the end of a river's journey, at the mouth. At the mouth of a river it can form deltas - for example, the Mississippi Delta.

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1) Explain the upper course of a river and what features it may from

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1) As the river moves through the upper course it cuts downwards. The gradient here is steep and the river channel is narrow. Vertical erosion in this highland part of the river helps to create steep-sided V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges. Interlocking spurs (look a bit like interlocking parts of zip) are when the river erodes the landscape in the upper course, and it winds and bends to avoid areas of hard rock. Rapids and waterfalls may from when a river runs over alternating layers of hard and soft rock.

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1) Explain the middle course of a river and what features it may form

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1) The river has more energy and a high volume of water. Gradient is gentle and lateral (sideways) erosion has widened the river channel. The river channel has also deepened. A larger river channel means there is less friction, so the water flows faster.As the river erodes laterally, to the right side then the left side, it forms large bends, and meanders.

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1) Explain how a meander is formed

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The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream. The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy due to decreased friction.On the inside of the bend, where the river flow is slower, material is deposited, as there is more friction. Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through, eg during a flood when the river has a higher discharge and more energy, and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake

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1) Explain the lower course of a river and what features it may from

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1) In the lower course, the river has a high volume and a large discharge. The river channel is now deep and wide and the landscape around it is flat. However, as a river reaches the end of its journey, energy levels are low and deposition takes place.The river now has a wide floodplain and Deltas can be found at the mouth of large rivers.

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1) what is a floodplain?

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1) A floodplain is the area around a river that is covered in times of flood. A floodplain is a very fertile area due to the rich alluvium deposited by floodwaters. This makes floodplains a good place for agriculture. A build up of alluvium on the banks of a river can create levees, which raise the river bank.

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1) what is a Delta?

2) what are the three main types of delta?

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1) A delta is formed when the river deposits its material faster than the sea can remove it.

2) 1. Arcuate or fan-shaped - the land around the river mouth arches out into the sea and the river splits many times on the way to the sea, creating a fan effect. 2. Cuspate - the land around the mouth of the river juts out arrow-like into the sea. 3.Bird's foot - the river splits on the way to the sea, each part of the river juts out into the sea, rather like a bird's foot.