Transcript Natural Hazards

Natural Hazards
Chapter 4
Natural Hazard
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What is a Natural hazard? Why should we study it?
 Natural events causing great loss of life or property
damage
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Different types of Natural Hazards:
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2004: Asian Tsunami: >200,000
1970: Bangladesh Cyclone: 300,000
1976: China earthquake: 300,000
Volcanism, earthquakes, Hurricane, tornado, Tsunami, Flooding,
Landslides
Damages from different types of Natural Hazards
Magnitude, frequency, catastrophe
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Impact of a disaster is related to magnitude (how big) and
frequency (how often). These two are inversely related. Actual
damage depends on other factors too, such as population,
climate, landuse, geology etc etc.
Catastrophe: immense damage: recovery and rehabilitation is a
long invloved process
Damages from Natural Hazards in US
Benefits of Natural hazards
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Flooding :
 deposits
fertile sediments in floodplains
 Nourishes beaches
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Volcano:
 Adds
landmass e.g., in Hawaii
 Produces fertile soil
 Created the atmosphere and hydrosphere
Evaluating Hazards
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Fundamental Principles:
 Hazards
are repetitive and predictable
 Risk Analysis is important for understanding
impact
 Hazards are linked, e.g., volcano, earthquake,
tsunami, landslide, flooding, forest fire..
 Human interference is magnifying damage
 Consequences can be minimized
Disaster Prediction
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Location:
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Probability of occurrence
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Volcanoes, earthquakes, landslide, flooding..often associated
with precursor events
Forecasting
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Hazards are cyclical,
With sufficient data probability of occurrence can be calculated
Precursor events
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e.g., Volcanoes and earthquakes along plate boundaries
Is possible by monitoring hazards e.g., hurricanes, tsunamis,
volcanic eruption etc
Warning
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Should be issued even at the risk of the hazard not materializing
Risk Assesment
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Risk Determination
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Acceptable Risk
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Risk= probability X damage
Risk-tolerance level of the society
Can vary: High for automobiles but low for nuclear accident
Problem and opportunities
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Lack of long term data– how do we calculate risk?
Information may be complex and difficult to analyze e.g., what is
the effect of radiation leak from a nuclear reactor?
Better risk assessment will lead to better decisions
Human Response to hazards
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Reactive – traditional response
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Impact
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Stages:
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Emergency: Search and Rescue, shelter, opening roads
Restoration: water and power, return to home, cleaning of rubble
Reconstruction I: Return to pre-disaster level
Reconstruction II: improvement
Rapid Restoration can be counter-productive
Anticipatory – a better way to reduce damage
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Direct (People killed, property damaged – affects individuals or small groups) and
Indirect effects (mental trauma, tax, donations—affects population)
Hazard perception by people and by government
Land-use planning: avoid hazardous locations
Insurance: often not extended to high risk areas
Evacuation
Disaster preparedness
Artificial control
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Difficult, expensive and often cause more harm
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Channelization of Kissimmee river
Sea walls, dams…
Future trends
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Global Climate and hazard
 Global
warming is increasing weather related
disasters
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Population and hazard
 Greater
population density leads to higher risk
 Change in land-use pattern magnifies
damages
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Recent floods in Haiti related to deforestation
. Global climate and hazards
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A. Global and regional climate change may
significantly affect incidence of storms,
landslides, drought, fires
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how climate change may affect magnitude and
frequency of natural events
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a. sea level rise may increase coastal erosion
b. shift in food production areas
c. expansion of deserts and semi-deserts
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warming of oceans will channel more energy from
ocean water into atmosphere
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likely will increase hazardous weather-related processes
Population increase, land-use
change, and natural hazards
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A. Population increase and hazardous events
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1. as population increases, need for planning to minimize losses from
natural disasters also increases
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a. more people at risk of an event
b. forces more people into hazardous areas
B. Land-use change and hazardous events
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1. past half-century has seen dramatic increase in great catastrophes
2. vast majority of natural disaster deaths between 1985-1995 were in
developing world
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a. Hurricane Mitch: hillsides stripped because of heavy rains on cleared and
burned land
b. Yangtze River: timber harvest and conversion to agriculture has increased
flood hazard