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Chapter 5

Introduction to Natural Hazards

Dr. Joao Santos

Chapter 5

Introduction to Natural Hazards

Dr. Joao Santos

Case History: Hurricane Katrina (1)

• Made Landfall in August 29, 2005 to the east of New Orleans

• Storm Surge: 3 to 6 m (9 to 20 ft)

• Diameter of serious damage path: About 160 km (100 mi)

• 80 percent of New Orleans under water

• Official number of deaths: 1,836

• Property damages: Tens of billions

• Estimated costs for recovering and rebuilding: hundreds of billions

Case History: Hurricane Katrina (2)

• Regional subsidence: 1 to 4 m (3 to 12 ft) per 100 yrs

• Sea level rise: 20 cm (8 in.) last 100 yrs due to global warming and extraction of GW, oil and gas

• Geographic location: Vulnerable to hurricanes, storms, and inland floods

• Aware of risks and warnings in place

• Insufficient funds for monitoring and maintaining the levee and floodwalls

• Poor coordination in initial emergency response efforts

• Rebuild: Better design and planning, better technology and knowledge, broader awareness

Hurricane Katrina

Figure 5.1

Natural Disaster, Hazards (1)

• Criteria: A particular event in which 10 or more people are killed; one hundred or more people are affected; a declaration of emergency is issued, or there is a request for international assistance

• Dangerous natural processes, including earthquakes, floods, volcanic activities, landslides, and storms

Natural Disaster, Hazards (2)

• The occurrences of natural disasters on a world scale are increasing

• Natural disaster causing great loss of life and/or property damage

• Earthquakes, floods, cyclones (hurricanes) killed several million people, with an average worldwide annual loss of life of about 150,000 people

• Annual average property damage exceeds $50 billion

• Impact risks, depending on the nature of hazards, spatial and temporal relations to human environment

Types of Natural Hazards

Why Natural Processes Become Hazards

• Natural processes become hazardous: When people live or work in areas where they occur

• Land-use changes, such as urbanization or deforestation

• Better environmental planning:Simply not to build on floodplains, earthquake prone areas

• Consumption of energy resources and climate changes

Hazard Magnitude and Frequency

• Magnitude: Intensity of a natural hazard in terms of the amount of energy released

• Frequency: Recurrence interval of a disastrous event

• Magnitude and Frequency: Generally an inverse relation between them

• More damages associated with hazards of moderate frequency and magnitudes

Magnitude, Frequency, and Impact Risk

• Magnitude and Frequency: Largely controlled by natural factors

• Impact risk: Controlled by both natural and human factors

• Low-magnitude and high-frequency hazards not always destructive, a high magnitude one almost certainly catastrophic

• Commonly, most impact risks from natural processes of moderate magnitude and moderate frequency

Mixed Blessings of Natural Hazards

• Not all hazardous processes exert harmful or deadly consequences

• Benefits: Creating new land, supplying nutrients to soil, flushing away pollutants, changing local landscape

• Fault gouge has formed groundwater barriers, producing natural subsurface dams and water resources

Damages of Natural Hazards (1)

• Death and damages: Great loss of human life, grave damages to property, changes in properties of Earth materials

• More life loss from a major natural disaster in a developing country; more property damage in a more developed country

• Catastrophe: Disastrous situations requiring a long process to recovery from grave damages

Catastrophic Potential of Hazards

Hazard Evaluation (1)

Fundamental Principles

• Most natural hazards: Identified and studied using the scientific method and predictable from scientific evaluation

• Risk analysis: A critical component in understanding impacts

• Different hazards are linked

• Hazardous events repetitive

• Importance of hazard planning and hazard mitigation

Hazard Evaluation (2)

• Study historic data: Hazards are repetitive events

– Occurrence and recurrence intervals

– Location and effects of past hazards

– Observations of present conditions

– Measuring the changes or rates of change

– Historic trends of hazards

Hazard Evaluation (3)

• Studying linkages: Spatial and temporal links

– Linkages between adjacent locations

– Linkages between past, present, and future conditions

– Linkages between hazards (e.g., volcano and mudflow)

– Geologic setting and hazards (e.g., rock fractures and landslides)

Disaster Forecast, Prediction, and

Warning (1)

• Forecast: The certainty of the event is given as the percent chance of happening

• Prediction: Sometimes possible to accurately predict when, where, type and size of the certain natural hazardous events

• Warning: A hazardous event has been predicted or a forecast has been made, the public must be warned

Disaster Forecast, Prediction, and

Warning (2)

• Locations, precursors, probability of occurring

• Determining the probabilities of a hazardous event at a given magnitude

• Observing precursor events or signs

• Forecasting the hazard

• Warning the public

Disaster Prediction and Warning (2)

Figure 5.14

Scientists, Hazards, and the Media

• The media are generally more interested in the impact of a particular event on people than in its scientific aspects

• Good relations between scientists and the news media is a goal that may be difficult to always achieve

• Scientists have an obligation to provide the public with information about natural hazards

• Reports concerning people’s lives and property should be conservative evaluations based on the evidence at hand

• Provide their readers, viewers, or listeners with accurate information that have been verified

Risk Assessment

• Risk determination

– Type, location, probability, consequences

– Risk estimate: Product of probability and consequences

• Risk Threshold: Acceptable risks

– Put probability and consequences into perspective

– Society’s perception and willingness

• Limitations and opportunities of risk assessment

Risk Impact (1)

Hazardous Earth processes and risk impact statistics for the past two decades

• Annual loss of life: About 150,000

• Financial loss: > $50 billions

• More life loss from a major natural disaster in a developing country (2003 Iran quake, ~30,000 people)

• More property damage occurs in a more developed country

Risk Impact (2)

Risk impact estimation:

• To human life: Potential loss and injury of life

• To property: Damage and destruction

• To society: Services and functions of society

• To economy: Manufacture, mining, commercial, real estate, etc.

• To natural environment: Direct or indirect adverse impact

Human Response to Hazards (1)

Reactive response

• Primarily after the hazardous event

• Recovery phases: Search response, rescue, restoration, and reconstruction

• Recovery period: Recovery length depending on the magnitude of hazard and impact intensity

Human Response to Hazards (2)

Reactive response and recovery priority

• Critical needs: Emergency operations, critical infrastructure, hospitals, shelter, food, and water supply

• Essential function: Transportation, communication, education, and other services

• Improvement and development: Rebuild damaged structures and develop better structures

Human Response to Hazards (3)

Anticipatory Response: Perceiving, Avoiding, and Adjusting to Hazards for avoiding or minimizing the impacts of disasters

• Land-use planning

• Insurance and other regulations for safety measures

• Evacuation

• Disaster awareness and preparedness: Individuals, families, cities, states, or even entire nations can practice

Human Response to Hazards (4)

General response in a given location

• Combination of reactive and anticipatory response

• Artificial control of natural processes

• Taking no or little action, being optimistic about chances of making it through disasters

Global Climate and Hazards

Population Growth and Natural Hazards

• Increase in population puts a greater number of people at risk

• Asia suffered the greatest losses from 1985 to 1997, with 77 percent of the total deaths and 45 percent of the economic losses

• Deadly catastrophes resulting from natural hazards linked to changes in land use, Hurricane Mitch in 1998, flooding of the Yangtze River in 1998, and Hurricane Katrina in 2005

• In quest: Artificially controlling some natural hazards

Land-Use Change and Natural Hazards (1)

• Land-use change amplifying the impact risks of natural hazards

• Deforestation and fire in Honduras before Hurricane Mitch, 11,000+ deaths – Massive deforestation in major river basin (e.g.,

85 percent forest loss in Yangtze River, 4000+ deaths)

– Inappropriate construction code in tectonic earthquake zone, 2003 Iran earthquake, ~300,000 deaths

– Poor construction in Haiti, 2010 earthquake, above 300,000 death

Land-Use Change and Increase in

Natural Hazards (2)

Applied and Critical-Thinking Topics

• List all the natural hazardous processes in the are where you live. What is done? What is more to be done?

• Construct a U.S. vulnerability map of natural hazards by state, or construct a state map by county.

• What is the difference between forecasting and warning

• Can humans eventually control the impact risks of natural hazards? Explain your rationale.

End of Chapter 5