Earth Hazards Case Studies

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Case studies for mudslides, flooding, earthquakes and volcanoes.

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Earth Hazards ­ Case Studies
The Venezuelan Mudslides
Natural factors:
Unusually high amount of rainfall
Human factors:
Corrupt politicians and bad planning from previous governments
Social impacts:
Many died
Many homeless
Communities and settlements destroyed
Economic impacts:
Buildings and infrastructure destroyed and need to be replaced
Oil leaks
Over US$3 billion to recover
Environmental impacts:
Ecosystems damaged by oil
Short term response:
Search and rescue operation
Emergency relief
Long term response:
Government rebuilt

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Earth Hazards ­ Case Studies
The Aberfan Disaster, 1996
Waste coal tip at steep angle
Prolonged heavy rain
Tip built on spring
Little vegetation on the tip to bind it
No management of the tip
It was assumed that any slide would be slow
147 killed (116 school children)
20 houses and a farm buried
Huge psychological impacts
Loss of a generation
Cost of clean up
Short term responses:
Emergency rescue services
People stopped work to help out
Long term responses:
Other tips…read more

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Earth Hazards ­ Case Studies
In the 1970's the sea was eroding the cliffs at a rate of approximately 1m per year
Rotational slip
Gulley's in the cliff face (incision in the cliff face)
The sea was eroding the bottom of the cliff by LSD moving from west to east
Human interference added to the problem.…read more

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Earth Hazards ­ Case Studies
Swiss Alps, Jan 2007
Heavy snowfall ­ 75cm
Mild winter
Trees had been removed to help skiers
Strong winds built up drifts
Skiers were going off piste
Reshaping of slopes for hotels
8 killed
Some buildings damaged
Damage to ski slopes
High cost of recue services
Roads blocked
Short term responses:
Rescue services
Long term responses:
Fencing off avalanche prone areas
Structures designed to slow and divert avalanches
Warnings and education
Setting off potential avalanches
4…read more

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Earth Hazards ­ Case Studies
Coastal flooding case study: North Sea
Storm surge, 1st Feb 1953
Physical causes
Storm surge ­ strong winds from NE pushing water South
Intense depression so sea level rises (1cm per 1mb fall)
High spring tide
North Sea narrows to South
Heavy rain so rivers swollen
Shallow coastal waters and low lying coast
Human causes
Dredging of sand offshore reduced coastal protection
Neglected sea walls
Global warming = sea level rise
Salt marshes reclaimed
Rivers embanked
Rapid urbanisation of coast…read more

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Earth Hazards ­ Case Studies
Short term
Evacuation of people and livestock
Search and rescue
Property pumped out
Army called in to seal sea walls
Long term
Early warning system with sea level monitoring
Sea levels raised or managed retreat accepted
Areas allowed to flood to take pressure off walls
Flood barrages on rivers
The Thames Barrier: 10 steel gates which rotate to hold back water and prevent it from
reaching the capital.…read more

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Earth Hazards ­ Case Studies
Why did Chiswell used to flood?
If the backwash is greater than the swash the beach is reduced so it is easier for the waves
to break over the crest of the beach
Percolation flooding is when the beach becomes completely saturated so the water just
passes through it
Heavy precipitation increases water level
What happened in December 1978 and February 1979?
Wave height of about 4.…read more

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Earth Hazards ­ Case Studies
The sheet steel piling (wave wall) has partly been pushed out of place in areas by hydraulic
The storm of 1989 had minimal impacts on Chiswell showing that the schemes were a success
The council has started to build new houses in the former flood risk areas
8…read more

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Earth Hazards ­ Case Studies
Bangladesh Flood, 1998
Most of Bangladesh is river delta
Most of the country is low lying and flat
Over half the land is below 5m above sea level
Cannot afford to invest in flood defences
Lack of doctors
Large population
Intense monsoon rainfall
Ganges water level rose by 2m in one month
Brahmaputra exceeded flood level July ­ September
Sea level in Bay of Bengal was 5.…read more

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Earth Hazards ­ Case Studies
Forecasting ­ Predicting with measuring of rainfall, river flow and weather patterns
10…read more


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