Flooding on the Yangtze River, China

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  • Created by: emma why
  • Created on: 03-04-14 09:17
What is the main input to the hydrological system of the Yangtse towards the north-west ?
Snowmelt from Tibetan Plateau
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What is the main input to the hydrological system of the Yangtze towards the north-east?
Monsoon rains moving from east to west up the Yangtse basin
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How many main tributaries does the Yangze have?
Six major tributaries
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What is there occasional input into the Yangtze hydrological system from?
Tropical storms
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What do some of the tributaries encourage at major junctions? (due to something called 'network geometry'?)
Floodwave magnification
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What is the headwaters of a river?
Source
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What can the source be defined as?
is the furthest place in that river or stream from its estuary or confluence with another river, as measured along the course of the river
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What is the impact of high relief in the headwaters of the Yangtze?
Rapid response to rain or snowmelt
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The Yangtze is the longest river in Asia, what does it rank as globally?
The third longest river in the world
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Where is the source of the Yangtze?
In Quinghai Province
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Why is precipitation high at the source of the Yangtze?
Height of the mountains
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What is the altitude in the Qinghai-Tibet plateau where the Yangtse is at its source?
Over 5000m
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What is the drainage basin area of the Yangtse?
Over 1,800,000km2
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What is the average discharge of the Yangtse?
31,9000m3/s
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How is Yangtze spelt?
With a Z
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What is the Chinese name for the Yangtze river?
Chang Jiang
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In China, what percentage of economic losses by all natural disasters are caused by flooding and meteorological disasters?
70%
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What does metereology involve?
Study of atmosphere
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In China each year what does the crop area damaged by meteorological disasters exceed?
50 million hectares
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How many in China each year are affected by meterological disasters?
Over 400mn
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What is the total loss due to meteorological disasters in China?
3-5% of GDP
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Inflooding in the early 21st century, how many deaths were caused by flooding of Yangtze?
3700
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What factors have influenced flooding of the Yangtze in recent years?
Monsoon rains, destruction of the levees, deforestation, heavy rainfall and rapid snowmelt
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Factor Influencing Flooding - Monsoon Rains
In the early part of the 20th century monsoon raisn caused deaths on the Huang He and Yangtze
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In the early 20th century, how many deaths were caused by monsoon rains on the Haung He and Yangtze?
100,000 deaths
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In 1938 how many deaths occurred due to the destruction of the levees by military?
Over 1 million deaths
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When was rainfall along the Yangtze River at the highest level ever recorded?
November 1997 to April 1998
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When did the most serious snowmelt disaster of the 20th century on the Quinghai-Tibet plateau occur?
Between November 1997 to February 1998
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What percentage of the watershed's original tree cover has been removed?
Up to 85%
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What can a watershed also be referred to as?
Drainage basin
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What has left the flood plain inadequately protected?
Incomplete levees
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Generally, what are the reasons for increasing disaster losses on the Yangtze?
Population growth, environmental degradation, urbanisation and industrialisation, land use and planning, poor housing conditions, inadequate prevention capacity and preparation, climate change
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Why can population growth lead to increase in disaster loss?
High population density means likelihood of more deaths in event of disaster
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What has forced people to settle on vulnerable flood plains and hillside?
Growing population pressures
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What do satellite photographs taken of the Yangtze River over the past decade show?
Increasing numbers of people moving into the most flood-prone areas
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In 1985 what was the approximate population of the Yangtze?
360,000,000
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In 2005 what was the approximate population of the Yangtze?
420,000,000
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What does environmental degradation lead to?
Increases chance of flooding and landslides
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What are examples of environmental degradation in river basins such as the Yangtze?
Deforestation, excessive land reclamation, large scale road construction, mining, mining in mountainous areas and wetlands destruction
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How much has soil erosion rate along the Yangtze River risen by since the 1950s?
40-50%
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What has exacerbated the problem of landslides and floods in recent years?
Deforestation and construction of dams
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Why have there been large increase in number of landslides along the shorelines of the reservoir created by the Three Gorges Dam?
Dam has created higher water levels
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What are dykes?
Artificial embankment to protect low lying land from flooding
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What has been the impact of dykes in the Yangtze river basin?
Hemmed in the Yangtze River and has eliminated wetlands
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During the 1950s what did the forest cover of Sichuan province fall from and to?
From 19% to about 6.5%
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During the 1950s what was significant about the rate of tree cutting in Sichuan province?
Was over double the natural tree growth rate
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What is the impact of destruction of forests?
Results in natural water storage loss and silting of rivers/lakes, also raises level of river bed
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What is the tree situation like in the upper catchment of the Yangtze?
Still contains large areas of mixed forests with tree roots stabilising soil so that water can infilitrate
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Without forests what would happen?
Large amounts of rainwater falling in mountains would run-off quickly into the river
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What do people living in areas of the Yangtze river basin use the forests for?
Firewood, food and living in - there is plenty of fallen dead wood to be used and in towns timber for building
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Since when has felling been banned in the upper catchment of the Yangtze?
1998
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In Huize County, there was originally 40% forest cover. What has that been reduced by in 40 years?
Has been reduced by 50% to only 20% forest cover
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What is there now a policy of regarding trees?
Afforestation on denuded land
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What is the issue with the current policy of afforestation?
Trees take time to grow!
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What is denuded land?
Uncovered/stripped land
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Why is the loss of lake and pond surface area volume an important cause of flooding?
Because there is less space to store water naturally in the flood basin
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Which lake is a major regulator of hte Yangtze floods that shrunk from 6000km2 in 1700 to 2820km2 by 1980?
Dongting Lake
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Although Dongting Lake has shrunk in size, what size can in reach in times of flooding?
20,000km2 as water and sediment from Yangtze flows in
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Why is Dongting Lake now only the second largest lake in China when it was the largest?
Land reclamation for farming
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What is a joint Norwegian-Chinese project on the Yangtze which began in 2005 and according to 2007 China Daily article, hopes to restore sustainable biodiversity to Dongting Lake area within 5-10 years?
Sino-Norwegian Project of Biodiversity Protection Management
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What does rapid urbanisation lead to?
Bigger and more frequent floods on one hand and also larger economic losses
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What do urban areas create?
Impermeable surfaces
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What happened when the government of Hunan Province tore down a km of dikes in order to open up new agricultural land in May 1992?
80,000 hectares of farmland and 700,000 lost their protection from flooding
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What does using land for pasture result in?
As vegetation is not allowed to regenerate - leaves the land left as scrub vegetation
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Why were large areas of land deforested to provide fuel to power furnaces?
Due to Mao Zedong's policy of building steelworks in the mid-1950s
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What has happened since the closure of steelworks?
Land terraced but only buckwheat grown as soil is so poor
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What is an issue with the terraces created after closure of steelworks?
Many poorly constructed
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What happens during periods of heavy rain with the terraces?
Water runs of hillside quickly and takes nutrient rich topsoil with it
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When heavy rain falls on hillside, where there is poor quality land, why is there increased risk of flooding?
Minimum interception and infiltration
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Other cards in this set

Card 2

Front

What is the main input to the hydrological system of the Yangtze towards the north-east?

Back

Monsoon rains moving from east to west up the Yangtse basin

Card 3

Front

How many main tributaries does the Yangze have?

Back

Preview of the front of card 3

Card 4

Front

What is there occasional input into the Yangtze hydrological system from?

Back

Preview of the front of card 4

Card 5

Front

What do some of the tributaries encourage at major junctions? (due to something called 'network geometry'?)

Back

Preview of the front of card 5
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