GLG 110
Part 2
Chapter 5
Introduction to Natural Hazards
5.1
Hazards, Disasters, and Natural Processes
Annual loss of life: about 150,000
Hazards include: earthquakes, floods, cyclones, hurricanes
Financial loss: exceeds $50 billion
Impact of natural disasters is high due to population density and land-use
patterns
Natural hazards are natural processes
Environmental geologists identify processes and pass on info to authorities
Unfortunately, many people question our suggestions
Frequency of natural disasters is inversely related to their magnitude
Benefits
of Natural Hazards
River flooding provides nutrients
Erosion provides sediment for beaches and flushes out pollutants
Landslides provide materials for dams in mountainous regions
Volcanic eruptions provide new land, nutrients for soil
Earthquakes provide subsurface barriers for water, build mountains
Death
and Damage Caused by Natural Hazards
The most deadly natural hazards are commonly not the most costly ones
Individual events vary greatly in their effect on property and human life
Each natural hazard has the potential of becoming a catastrophe
Catastrophe potential of natural hazards may vary due to changes in land-use
patterns
5.2 Evaluating Hazards: History, Linkages, Disaster Prediction, and Risk Assessment
Disaster prediction is an important endeavor
In most instances we do not have enough info to predict
Therefore we look for patterns in past history to predict range of possible
problems
Disaster Prediction and Warning
To predict a natural disaster we look for the following:
- location: we know where certain events have taken place (e.g. earthquakes)
- probability of occurrence: based on probability and chance (e.g. river flooding)
- precursor events: many events have some type of precursor event associated with it (e.g. earthquakes)
- forecasting: some events are seasonal (e.g. hurricanes, floods)
- warning: scientists analyze data and pass the warning to officials, media usually reports only “half the truth”, and people don’t take warnings seriously
Risk Assessment
Risk assessment is a steadily growing field
Risk: is the product of an event occurring times the consequences should it occur
Acceptable risk is more difficult to assess because situations do vary
The most important problem in risk analysis is lack of good data
5.3 The Human Response to Hazard
Primary ways to deal with disasters is reactive (following a disaster)
A better approach is to anticipate disasters, to be proactive
Reactive Response: Impact of and Recovery from Disasters
Disaster impact is either direct or indirect
Direct effect: people killed, injured, dislocated
Indirect effects: emotional distress, donation of money or goods, tax increase to
pay for damages
recovery stages after a disaster involve:
emergency work, restoration of services and communication lines, reconstruction
Anticipatory Response: Avoiding and Adjusting to Hazards
Perception of hazard by individual person is the key to hazard avoidance
The best adjustments to hazards is land-use planning
Other ways of coping with natural hazards:
Buying insurance (e.g. flood insurance, earthquake insurance)
Evacuation: timely removal of people (e.g. hurricanes, tornadoes)
Disaster preparedness: being trained to deal with disasters (e.g. earthquake drills)
Artificial control of natural disasters has had mixed success
“Just take a loss” attitude or “It won’t happen to me” attitude
5.4 Global Climate and Hazard
Global warming may seriously increase frequency of major natural disasters
Sea levels will rise, low areas will be flooded, deserts will increase in size, storms
Will occur more frequently
In 1998: 32,000 people killed and 300 million displaced by weather-related
disaster
5.5 Population Increase, Land-Use Change, and Natural Hazards
Population Increase and Hazardous Events
Population increase is a major environmental problem
More people settle in hazardous areas
e.g.
e.g. Armero (
town killing 21,000 people
Land-Use Change and Hazardous Events
Land-use change is trigger for natural hazards
e.g. Yangtze River (
- removal of forest by fire or down cutting leaves soil exposed
- rain washes soil downhill and may cause mudslides
Review questions are located on page 135.