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Ihsan Al-Aasm
Phone: (519) 253-3000 ext:2494

School of Physical Sciences

University of Windsor
401 Sunset Avenue Windsor, Ontario Canada N9B 3P4

Hazards, disasters, and natural processes

A. Natural disasters: loss of life and property damages
1. several million people killed since 1970’s
2. financial losses exceed $50 billion per year
3. natural disasters caused by natural hazards that have always existed
a. extent of disasters affected by human population density and land-use patterns

Why natural processes are sometimes hazards?
1. Natural hazards are basically natural processes
2. Natural processes become hazardous when people live or work in areas where the processes occur

Magnitude and frequency
Impact of event is a function of its magnitude and frequency
a. magnitude: amount of energy released
b. frequency: recurrence interval
c. magnitude and frequency are typically inversely related

Impact of an event is also a function of other factors

a. climate
b. geology
c. vegetation
d. population
e. land use

3- Frequency of event is generally inversely proportional to its magnitude

D. Benefits of natural hazards

Dangerous natural events also provide benefits or natural service functions
a. flooding causes erosion in mountains but delivers sediment to beaches and flushes pollutants from estuaries
b. landslides can create mountain lakes
c. volcanic eruptions provide numerous benefits
d. earthquakes can create fault gouge, which can influence water resources

Death and damage caused by natural hazards
1. Greatest loss of human life is not necessarily correlated to extensive property damage
2. Potential to produce catastrophe is an important aspect of all natural hazards
a. hazards most likely to produce catastrophe
1. floods
2. hurricanes
3. tornadoes
4. earthquakes
5. volcanic eruptions
6. large wildfires

Effects of natural hazards change with time
a. changes in land-use patterns cause development on marginal lands
b. urbanization changes physical properties of Earth materials
c. increasing population puts more people at risk

Evaluating hazards: history, linkages, disaster prediction, and risk assessment

A. Role of history in understanding hazards
1. hazards are repetitive events
a. studying their history provides information for hazards reduction

Example: flooding
a. historic information
b. prehistoric information from geologic environment
c. to understand nature and extent of flood hazards, must understand occurrence, location and effects of past floods
d. present conditions and recent land-use change must be integrated with historical information

Linkages between hazardous events

1. Many hazards are linked
a. examples: hurricanes associated with flooding, coastal erosion, landslides
2. Natural hazards and characteristics of Earth materials are linked
a. example: shale is prone to landslides

Disaster prediction and warning
a. typically we know where a particular kind of event will occur
b. regional scale: general distribution of hazards
c. local scale: need to study details

Probability of occurrence
a. determining probability of event within particular time span is an essential goal of hazard evaluation
b. example: flood hazards
Precursor events
a. help predict when and where an event is likely to happen
b. examples: creep of ground prior to landslide, swelling of a volcano

a. determine when certain natural events are likely to occur
b. examples: flood stage forecasting, hurricane forecasting, tsunami forecasting
a . alerting public once a hazardous event has been forecast or predicted
b. concerns include unreliable predictions and poor communication between scientists and the media
c. false warnings may ultimately help disaster preparedness

Risk assessment
1. Risk determination
a. risk is the probability of an event multiplied by the consequences (e.g. damage to people, property, etc) should it occur
2. acceptable risk
a. the risk that society or individuals are willing to endure
b. determination is complex and dependent upon the situation

Problems and opportunities for risk assessment

a. lack of reliable data is often a major problem
b. improvement of methods of prediction has occurred in some areas, as has improvement of ability to estimate consequences

The human response to hazards
A. Reactive response: impact of and recovery from disasters
1. response after a disaster
a. search and rescue
b. firefighting
c. providing emergency food, water, shelter

Direct effects of disaster
a. people killed, injured, displaced, or otherwise damaged
b. felt only by individuals immediately affected
3Indirect effects of disaster: responses
a. emotional distress, donation of money or goods, paying taxes to finance recovery
b. felt by the general populace

Stages of recovery
a. emergency work
b. restoration of services and communication lines
c. reconstruction

Anticipatory response: perceiving, avoiding, and adjusting to hazards
1. hazard perception
a. government
b. public
2. land-use planning
a. avoiding construction on floodplains, areas of active landslides, places where coastal erosion is likely to occur, etc.

3. insurance
4. evacuation
a. concerns include timely public response to warnings and potential for panic at last minute
5. disaster preparedness
Artificial control of natural processes
1. attempts have met with mixed success

IV. 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
a. likely will increase hazardous weather-related processes

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

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