Natural Hazards Case Studies
- Created by: Bethany Ball
- Created on: 10-06-14 16:05
Mass Movement
Hollbeck hall 1993
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A landslip along the upper sections of boulder clay, at the 60m cliffs in Scarborough.
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Destroyed the 1883 Hollbeck hall.
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Its part of the most rapidly retreating area in Britain; would have cost too much to protect it.
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Agriculture blamed droughts for making the land unstable.
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It rained, the clay became saturated, causing an earth flow.
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Nothing to do with erosion.
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Nothing could be done until the slope slid to 25 degrees.
Swiss Alps 2007
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Avalanche
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Caused by: Heavy snowfall 75cm, mild winter so warmer layers, trees removed to help skiers, strong winds built up-drift, skiers went off piste, slopes reshaped for hotels.
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Impacts: 8 killed, some damage to buildings, high cost of rescue services, roads blocked.
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Responses: short term – rescue services, helicopters. Long term – fence off avalanche prone areas, structures to slow or divert avalanches, warnings and education, setting off potential avalanches, reforestation.
Aberfan 1966
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Flow/landslide
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Causes – Waste coal tip at a steep angle, prolonged heavy rain, tip built on a spring so water seeped through sandstone, little vegetation to bind the waste, no management of tip, assumed any slide would be slow.
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Impacts – 147 killed, 116 were children, 20 houses and a farm buried, huge physiological impact, loss of a generation, cost of clean up, it was slow enough to give a warning.
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Responses – short term: emergency rescue services. Long term: £20 million in clean up, no prosecutions, over £20 million in donations, 1969 Mines and Quarry Act passed which controls the siting of tips, other tips checked and their slope angles reduced.
Venezuelan Mudslide 1999
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High rainfall (410mm in one day)
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Precipitation 40% higher than average.
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Started with an avalanche of rocks/mud pour down slopes of 2000m Mt Avila, burying 300m of land.
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The rain triggered mudslides, landslides and flash floods that killed 30-50,000 people in a ***** between the mountains and the Caribbean sea.
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150,000 became homeless.
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Slums were buried and swept out to sea.
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The mud was 30ft deep.
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Infrastructure was destroyed.
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Airport closed
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Ports flooded so supplies couldn’t be brought in.
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Container ships were damaged and hazardous materials leaked.
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Total cost $3 billion.
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Blamed corrupt politicians for allowing shanty towns to develop around the mountain.
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Search and rescue, few survivors found.
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Emergency relief, accommodation, food, water and medicine.
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Encouraged people to move away from overcrowded coast.
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Government announced it was to expend the city and build homes in the north coastal region.
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Reconstruction of canels and ports.
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Vargras built quickly.
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The town ruined was replaced with parks.
Flooding
North Sea Storm Surge 1953
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Physical causes – Storm surge: strong winds from north/east pushing water south, intense depression so sea level rose, high spring tide, north sea narrows towards south so greater wave size, heavy rain so rivers swollen.
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Human causes – Dredging of sand offshore, neglected sea walls, global warming so sea level rise, salt marshes reclaimed, rivers embanked, rapid urbanisation of coast, encroachment onto natural flood holding areas.
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Enviro impacts: Land lost to…
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