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17 Cards in this Set

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Name and describe the features of a drainage basin, including watershed and channel network – River Tay, UK.
- 119 miles long – the longest river in Scotland and the seventh-longest in the United Kingdom
- Starts in the mountains in the West of Scotland and flows east, through Perth and Dundee and flows into the North Sea
River Tay: Upper Course
Characteristics of river - small channel, fast flowing, high energy. Falls of Acharn near Kenmore
Waterfalls are a popular tourist resort
V-shaped valleys steep and narrow
Characteristics of Landscape - Wet marshy hilltop
Rain collects and forms into channel, Water forced down by gravity – Energy builds = vertical erosion.
Other facts - Sheep farming
On one of the Tay’s major tributaries – River Tummel – provides 1/5th of water supply by HEP
River Tay: Middle Course
Characteristics of River - Tributaries common (River Tummel), Wider river that begins to meander, interlocking spurs, dark brown water due to load, higher velocity.
Characteristics of Landscape - gentler slope. When river floods it spills out onto flat land – flood plain
River Tay: Middle Course
Landforms: Meanders, rapids, river cliffs
Uses of Land and River: Fertile soil is ideal for arable and mixed farming – farmers can’t prevent flooding so they have to work around the river’s regime (timetable). Rivers provided a transport route through inaccessible areas. Settlements flourished like Dunkeld which was a major religious centre. Important for industry – power used for water wheels to power textile mills and factories.
Controversy - Tourism is important (economically and socially) to the people who live along the River Tay but there different needs result in conflict. Anglers are unhappy that sporting activities such as white-water rafting is taking place on the river because this activity unsettles the fish.
River Tay: Lower Course
- very short
Characteristics of River: much wider and deeper
Landforms: Ox-bow lakes, meanders, estuaries
Processes: Little energy to carry load of material so it deposits them as islands or deltas. Because of amount of deposition dredgers often have to dig out sand to enable shipping but sand doesn’t go to waste – sold to other parts of Britain.
Uses: Delta on Tay is used as a golf course since it is very flat
Explain why rivers flood – Boscastle, UK - background information
In Boscastle, north coast of Cornwall, 60mm of rain fell in 2 hours – the equivalent to the area’s average August rainfall. There were numerous causes to the short lag time. 2 rivers – Valency and Jordan
Physical Causes of Boscastle Flood
- Very steep gradient
- steep valley sides caused quick surface run-off
- ground and river was saturated due to heavy rain
- The weather on the 16th August was extremely hot, causing convectional rainfall
- 12cm of rain fell in 6 hours
Physical Causes of Boscastle Flood
- The narrow valley, small river channel and fast surface run-off caused the river to reach bank full discharge very quickly - short lag time
- Much of the valley rock is impermeable which shortened lag time
- The valleys of North Cornwall are known as ‘flashy catchments’ and as they are short and steep, water was accelerated down the hills. The Valency is very narrow which led to a high discharge descending into the valley.
- Relief – Boscastle is bottom of a steep hill so like a funnel it attracts more overland flow
Human Causes of Boscastle Flood
- no flood barriers
- The sewer and drainage system in Boscastle were very old so they became full very quickly
- A bridge in the centre of Boscastle caused material to get stuck behind. This caused a temporary dam causing the river to flood around the village
- Boscastle was built in a narrow valley next to a river. Residents had never experienced a major flood event so were unprepared.
Human Causes of Boscastle Flood
- Although Boscastle is only a small urban area, urbanisation can contribute to flooding. Urbanisation creates impermeable surfaces which stops infiltration and increases surface run-off into rivers.
- Deforestation – the moor surrounding Boscastle has in the past been deforested which means there was less vegetation interception to slow the movement of water and increase lag time
Water storage project – Three Gorges Dam
(When was it started, aims etc.)
The Three Gorges Dam Project begun in 1994 and was completed in 2008. China is the world’s most populate country and has fastest growing economy. This project is also a symbol of the country’s rapid growth and development into a modern world economic power. The reason it was constructed is to reduce flooding, to improve navigation for shipping and to generate electricity via HEP (3 aims).
Environmental Successes
• The energy produced will meet 10% of China’s present electricity needs – as it is 3rd largest river in world it offered huge HEP potential
• Equivalent to 50 million tons of coal so is reducing the greenhouse gas emissions
• Increase irrigation water for cropland below dam
Social Successes
• The dam will become a tourist attraction and will attract a lot of people to the area. Many tertiary sector/service jobs will be created.
• Reduces chance of downstream flooding for 15 million people
Economical Successes
• Larger ships can navigate river therefore there are more ports + trade
• More tourism
• China will prosper; government will like it as it makes them appear more powerful
Environmental Weaknesses
• Some animals are threatened – the baiji or Chinese river dolphin became extinct in 2006
• Environmentalists have questioned the wisdom of the whole project. They argue that a series of smaller HE dams on the tributaries of the Yangtze would have been a more efficient way of generating electricity and reducing risk of flood.
• There is still some flooding downstream
• Silt-built up behind the dam – around 250 million tonnes of silt could be deposited behind the dam every year – this could reduce the storage capacity of the reservoir AND increase river and coastal erosion downstream
• This silt-build up is shrinking the wetlands at the mouth of the Yangtze near Shanghai, the winter home of 95% of the remaining population of the endangered Siberian crane
• The water in reservoir is becoming heavily polluted from shipping and waste discharged from cities
• Dam is located in a tectonically active region
Social Weaknesses
• 1.4 million People were forced to move homes to accommodate the dam, reservoir and power stations. Those displaced were promised compensation for the losses but many have not received this.
• Cultural monuments have been lost including the Zhang Fei Temple
• POLITICAL – war; dam is a vulnerable target
Economical Weaknesses
• Cost £25 million to build
• Dredging that will be necessary is expensive