Unit 2 - Natural Environment: River Landscapes Flashcards
(77 cards)
0
Q
Define solution
A
Minerals that are dissolved in the water and are carried around in solution
1
Q
Types of transport
A
Solution
Suspension
Saltation
Traction
2
Q
Define suspension
A
Fine light material that is carried along in the water
3
Q
Define saltation
A
Small pebbles and stones are bounced along the river bed
4
Q
Define traction
A
Large boulders and rocks are rolled down the river bed
5
Q
What is a drainage basin??
A
The geographical area drained by a river and its tributaries, area of water runoff. The area that covers all tributaries and the mouth
6
Q
Define source?
A
This is were the river starts. Many sources form small streams that form together to make a big river.
7
Q
Define watershed?
A
The boundary between to drainage basins, normally marked by a high point of land.
8
Q
Define tributary
A
These are small streams connecting the sources to the main rivers.
9
Q
Define hydraulic action?
A
The force of the river against the banks can cause are to be trapped in the cracks and crevices. The pressure weakens the banks and they will eventually fall away.(worn away)
10
Q
Define corrasion?
A
Waves carrying debris such as sand shingle and pebbles and hurled against the sides of the river bank wearing it slowly away.
11
Q
Corrosion(solution)
A
This is a chemical process, certain chemicals in the river water wear away the minerals in the river bank in tern weakening it so it can be worn away.
12
Q
Define attrition?
A
Rocks being carried by the river smash together and break into smaller, smoother rocks and particles.
13
Q
Define abrasion?
A
Rocks being carried along by the river wear away the bottom of the river and also the river banks.
14
Q
What are the three main types of weathering?
A
Biological
Chemical
Physical
15
Q
Define biological erosion?
A
This is when plants and animals were away the rocks. Etc.. Burrowing animals weaken rocks or plant roots break up rocks.
16
Q
Define physical erosion?
A
This is caused by physical effects such as the wind, the rain the temperature (freeze-thaw)
17
Q
Define chemical erosion?
A
This is when rocks are eroded by chemicals such as acid rain. This dissolves the minerals in the rocks, in tern weakening them and becoming more susceptible to erosion.
18
Q
What are the two main methods of mass movement?
A
Soil creep
Slumping
19
Q
Define soil creep
A
This is when soil and rock slowly moves down a hill due to is mass and the pull of gravity. It moves faster when the soil is saturated due to rain fall.
20
Q
Define slumping?
A
This is when earth slides down a plain, often due to gravity and the weakness of the rock.
21
Q
Define rotational slumping?
A
This is when earth slides down a concave plate. Like a slide it moves outwards
22
Q
How many UK properties are at risk from flooding?
A
2.1 million
23
Q
how many UK properties are at risk from flooding on the coast?
A
1.05 million
24
What flood information will people find on the Environment Agency website?
Information on the likelihood of a flood, by issuing warning codes that show people how to react, also a hotline number.
25
In what other ways can flooding be reduced?
adding good flood defense into the design of the building, houses should not be built in areas where it is likely to flood.
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Where does flooding normally happen?
Normally an occurrence in the lower course of the river, hence why there is a flood plain.
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What are human causes of flooding?
- Ploughing up and down slopes rather than around them channels the rainwater to the river faster.
- Vegetation has been removed so there is less interception and water will move to the river more quickly
- Dams may burst which will cause excess water in river channels and flooding of large areas.
- of there is a town on a flood plain, storm drains will allow water to move into the river at a greater speed and so make flooding more likely.
28
What normally causes flooding?
It is normally a significant rainfall event:
- A long continuous period of rainfall which saturates the ground increasing overland flow.
- A 'cloudburst' or heavy thunderstorm which inundates an area.
- A sudden rise in temperature which rapidly melts snow and ice - often this run off cannot be absorbed as the ground remains frozen.
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How can households be helped to take precautions?
this is done in the UK through a chain of events,
- the met office predicts the likelihood of a river flooding.
- They then give the info to people via TV etc..
- tells people to be proactive and ring the flood hotline if there is anything wrong.
31
How does the Environment Agency flood warning system work?
- this shows people the likely hood of a flood in there area using a warning code.
- The ratings go FLOOD WATCH, FLOOD WARNING, SEVERE FLOOD WARNING, ALL CLEAR.
- Gives information to people of what they should do and what they should expect.
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Who are DEFRA?
The Department of Environment, Food and Rural Affairs.
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How can DEFRA help?
UK government department responsible for policy and regulations on environmental, food and rural issues. Our priorities are to grow the rural economy, improve the environment and safeguard animal and plant health.
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Negative impacts on flooding?
Floods can cause damage to homes and possessions as well as disruption to communications.
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Positive impacts of flooding?
Flooding deposits fine silt (alluvium) onto the floodplain, making it very fertile and excellent for agriculture. People living on or near floodplains may rely upon regular flooding to help support their farming and therefore provide food.
LEDCs tend to be affected more than MEDCs by the effects of flooding. This is partly because LEDCs have more farms, and farming communities are attracted to fertile flood plains. LEDCs often do not have the resources to prevent flooding or deal with the aftermath of flooding.
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Rivers, hard engineering techniques?
Embankments, channelization, Flood relief, Dams, flood walls and storage areas
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What are Embankments?
These are raised banks along the river.
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What is Channelization?
the river channel may be widened or deepened to carry more water. Or the river channel may be straightened so water can travel faster.
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What are Flood relief channels?
The channel course of the river can also be altered, diverting floodwater away from settlements.
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What are dams?
dams are built along the course of a river in order to control the flow. Water is held back and the dam releases water in a controlled way.
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Advantages and disadvantages of Embankments?
- Can be used as a path for pedestrians beside the river.
- Concrete embankments are very effective to erosion
- However the banks are often not built high enough, many people claim that they are ugly and spoil the view.
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Advantages and disadvantages of channelization?
- very effect, water moves away faster.
- Long lasting
- however flooding could happen down stream because water is carried faster.
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Advantages and disadvantages of Flood relief channels?
- Makes the people who live close to the main river safe as water is diverted into the relief channel.
- can be used for water sports.
- It requires vast amounts of land which can be expensive.
- It is also very expensive anyway to do.
44
Advantages and disadvantages of Dams?
- water is stored behind the dam and it can be used for hydroelectric power which is renewable energy.
- However is very expensive,
- sediment is trapped behind the wall leading to further erosion downstream.
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What are Flood walls?
A vertical barrier usually made of concrete.
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What are the advantages and disadvantages of flood walls?
- They can be used in areas where space is limited.
- Quick to put up
- However they need to be made well or water may come through the joints.
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What are Storage areas?
A large depression that is close to the river that will fill with water if the river overflows and therefore protect the surrounding land.
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What are the advantages and disadvantages of Storage areas?
- they are natural looking and do not damages the environment.
- they need a large amount of land and also only come in to use when the river floods.
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What are techniques of soft engineering?
Floodplain zoning
Washlands
Warning syestems
Afforestation
50
What is Floodplain zoning?
This is when local authorities and the national government introduce policies to control urban development close to the flood plain.
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What are Washlands?
The river is allowed to flood naturally in wasteland areas, to prevent flooding in other areas, for example near settlements/
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What are Warning systems?
A network of sirens which give people early warning of possible flooding. there are also other ways such as via TV radio and comms.
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What is Afforestation?
Trees are planted in the catchment area of the river to intercept te rainfall and slow down the flow of water to the river.
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What are advantages and disadvantages of Floodplain zoning?
- A very cheap way of reducing the risk of flooding to properties.
- There can be resistance to restricting development in areas where there is a shortage of housing.
- Enforcing planning permissions for this may be more difficult in LIC's.
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what are the advantages and disadvantages of washlands?
- Very cost effective because nothing is built and also provides habitats for animals.
- the deposition that occurs will help the land become for fertile.
- Large areas of land will not be built on and productive land may be turned into marshland.
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What are the advantages and disadvantages of warning systems?
- They are very cheap to install and are very effective
| - The sirens could be vandalized and there may not be enough time for residents to prepare for the flood.
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What are the advantages and disadvantages of Afforestation?
- This is relatively low cost and improves the quality of the environment, soil erosion is avoided
- It is often conifers that are planted which make the soil acidic, people complain that trees ruin the landscape.
58
What is Physical weathering?
This is when water gets into cracks in the rocks and then freezes and expands, this process is repeated until the rocks are broken off. this is hydraulic action.
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What is Chemical weathering?
This happens when rain water containing weak acids reacts with certain rock types, such as carbonates in limestone, this can cause the rocks to break up and disintegrate.
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What is Biological weathering?
this is the action of plants and animals such as when seeds fall into cracks and begin to grow forcing the rocks apart with there roots, also burrowing animals.
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The higher course of the river what are the characteristic?
The river is normally very shallow and narrow and is very fast moving. Normally a V-shaped valley. There is mostly vertical erosion with the a lot of erosion Hydraulic action, abrasion and attrition. Some traction and saltation at high flow. Deposition of large material and Large load.
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In the middle course of the river what are the characteristics?
the channel is wider and deeper, there is some vertical erosion; lateral erosion more important. Hydraulic action less important, suspension main transpiration; salutation and traction still present. Deposition more obvious and load size reduced.
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in the lower course of the river what are the characteristics?
Here is the widest, deepest channel. less erosion; only a little lateral. All erosion much less important. Suspension dominant. Deposition of fine material. Large amount of load, size now very small.
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what is discharge?
amount of water in the river and the speed of which it is traveling downstream.
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What is the channel depth?
this is the depth of the channel, the river gets deeper a the further it goes.
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What is the load quantity?
This shows how much sediment is in it. More sediment the further you are down stream.
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What is the bed roughness?
how rocky the river bed is, normally more rocky at the top.
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What does the upper course of the river normally contain?
Upper-course river features include steep-sided V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges.
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What does the middle course of the river normally contain?
Middle-course river features include wider, shallower valleys, meanders, and oxbow lakes.
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What does the lower course of the river normally contain?
Lower-course river features include wide flat-bottomed valleys, floodplains and deltas.
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How are interlocking spurs formed?
As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs, which look a bit like the interlocking parts of a zip.
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Why do waterfalls form?
Waterfalls form where the river bed has a layer of harder rock overlying the softer rocks.
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How are waterfalls formed?
- As water falls the softer rock is eroded much more quickly than the harder rock; therefore undercutting the harder rock.
- The hard, overhanging rock eventually collapses.
- The collapsed rocks fall into the plunge pool causing more erosion of the soft rocks and a deeper plunge pool.
- This goes on continuously causing the waterfall to retreat upstream.
- The waterfall leaves a steep sided gorge as it retreats.
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What are deltas?
Deltas are found at the mouth of large rivers - for example, the Mississippi. A delta is formed when the river deposits its material faster than the sea can remove it
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How are oxbow lakes formed?
In the lower course of the river, meander bends become very large. With continued erosion on the outside of the banks and deposition on the inside, the ends of the meander bend become closer. When flooding occur, the river is able to cut through the gap and, in time, forms a new straight channel . continued deposition results in the old bend being cut off resulting in a oxbow lake.
76
The characteristics of the river Nene?
- the river Nene is south of rutland.
- It runs south east of Leicestershire
- Rockingham forest makes it less likely to flood Trees take up 150 gallons of water
- Lots of meanders
- Many tributary (potential for lots of water to enter river)
- A short fat drainage basin
- The river runs from the south west to the north east
77
Case studies River landscapes?
Nene - Peterborough flooding
