Natural Hazards

1
Natural Hazards

• Chapter 4

2
Natural Hazard

• What is a Natural hazard? Why should we study it?
• Natural events causing great loss of life or
  property damage
• 2004 Asian Tsunami gt200,000
• 1970 Bangladesh Cyclone 300,000
• 1976 China earthquake 300,000
• Different types of Natural Hazards
• Volcanism, earthquakes, Hurricane, tornado,
  Tsunami, Flooding, Landslides
• Damages from different types of Natural Hazards
• Magnitude, frequency, catastrophe
• 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

3
Damages from Natural Hazards in US
4
Benefits of Natural hazards

• Flooding
• deposits fertile sediments in floodplains
• Nourishes beaches
• Volcano
• Adds landmass e.g., in Hawaii
• Produces fertile soil
• Created the atmosphere and hydrosphere

5
Evaluating Hazards

• 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

6
Disaster Prediction

• Location
• e.g., Volcanoes and earthquakes along plate
  boundaries
• Probability of occurrence
• Hazards are cyclical,
• With sufficient data probability of occurrence
  can be calculated
• Precursor events
• Volcanoes, earthquakes, landslide,
  flooding..often associated with precursor events
• Forecasting
• Is possible by monitoring hazards e.g.,
  hurricanes, tsunamis, volcanic eruption etc
• Warning
• Should be issued even at the risk of the hazard
  not materializing

7
Risk Assesment

• Risk Determination
• Risk probability X damage
• Acceptable Risk
• Risk-tolerance level of the society
• Can vary High for automobiles but low for
  nuclear accident
• Problem and opportunities
• 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

8
Human Response to hazards

• Reactive traditional response
• Impact
• Direct (People killed, property damaged affects
  individuals or small groups) and
• Indirect effects (mental trauma, tax,
  donationsaffects population)
• Stages
• 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
• 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
• Difficult, expensive and often cause more harm
• Channelization of Kissimmee river

9
Future trends

• Global Climate and hazard
• Global warming is increasing weather related
  disasters
• Population and hazard
• Greater population density leads to higher risk
• Change in land-use pattern magnifies damages
• Recent floods in Haiti related to deforestation

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. Global climate and hazards

• A. Global and regional climate change may
  significantly affect incidence of storms,
  landslides, drought, fires
• 1. how climate change may affect magnitude and
  frequency of natural events
• a. sea level rise may increase coastal erosion
• b. shift in food production areas
• c. expansion of deserts and semi-deserts
• 2. warming of oceans will channel more energy
  from ocean water into atmosphere
• likely will increase hazardous weather-related
  processes

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Population increase, land-use change, and natural
hazards

• A. Population increase and hazardous events
• 1. as population increases, need for planning to
  minimize losses from natural disasters also
  increases
• a. more people at risk of an event
• b. forces more people into hazardous areas
• B. Land-use change and hazardous events
• 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
• 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