Unit+1.+Intro+To+Nat+Hazards+Eesa05

Unit 1 Introduction to Natural Hazards

EES A05 H3

Marco A. Belmont

Nevado del Ruiz, Colombia, 1985

• In 1845, the Colombian volcano erupted and a mudflow killed approximately 1,000 people.

• Deposits from this event produced rich soil in the Lagunilla River valley, enticing people to move there and establish farms.

• The town of Aramero became the agricultural centre for the valley and in 1985 had grown to a population of 23,000.

Nevado del Ruiz• On November 13,

1985, a small eruption of the Colombian volcano produced another mudflow that buried Aramero.– 21,000 people death– $200 million in

property damage

Nevado del Ruiz

Nevado del Ruiz

Nevado del Ruiz

Nevado del Ruiz• A review of the history of Nevado del Ruiz

shows that:– The 1985 eruption and mudflows were

predicted, the hazard identified, and the risk evaluated.

– Population growth since the last mudflow in 1845 greatly increased the number of people at risk

– The tremendous loss of life could have been significantly reduced if warnings had been heeded.

Importance of studying natural hazards

• The world can experience devastating natural events like earthquakes, tsunamis, volcanic eruptions, hurricanes, tornados, etc.

• This events are the result of enormous forces that are at work both inside and on the surface of our planet.

• In this course we will study these forces, how they interact with our civilization, and how we can better adjust to their effects.

Internal and External Processes

• Process.- the physical, chemical, and biological ways by which events such as volcanic eruptions, earthquakes, landslides, and floods, affect Earth’s surface.

Internal Processes• Some processes, such

as volcanic eruptions and earthquakes, are the result of internal forces deep within Earth.

• Most of these internal processes are explained by the theory of plate tectonics.

External Processes

• Other processes associated with natural hazards result from external forces that are at or very near Earth’s surface.

• An example of these external processes is the fact that the energy from the Sun warms the Earth’s atmosphere and surface, producing winds and evaporating water.

External Processes

• Wind circulation and water evaporation are responsible for forming Earth’s climatic zones and for driving the movement of water in the hydrologic cycle.

• These external forces are in turn directly related to hazardous processes, such as violent storms and flooding, as well as coastal erosion.

Internal and External Processes• Therefore, hazardous processes result from

internal heating of Earth or from external energy from the Sun.

• The energy released by natural processes varies greatly. For example:– the average tornado expends about 1,000

times as much energy as a lighting bolt,– the volcanic eruption of Mount St. Helens in

May 1980 expended approximately 1,000,000 times as much energy as a lighting bolt.

Internal and External Processes

• Events such as earthquakes, volcanoes, floods, and natural fires are natural processes that have been occurring on Earth’s surface since long before it was populated by humans.

• These natural processes become hazardous when human beings live or work in their path.

Hazard, Risk, Disaster, and Catastrophe

• A natural hazard is any natural process that poses a threat to human life or property.– The event itself is not a hazard; rather, a

process becomes a hazard when it threatens human interests.


• Risk may be expressed as the probability that a destructive event may occur multiplied by the event’s likely impact on people and property.

• Risk thus integrates hazard and social vulnerability.


•• A natural disaster is the effect of a hazard

in society, usually as an event that occurs over a limited time span in a defined geographic area.– The term disaster is used when the interaction

between humans and a natural process results in significant property damage, injuries, or loss of life.


• A natural catastrophe, simply put, is a massive disaster, requiring significant expenditure of time and money for recovery.

Major hazards in the USA(not including blizzards and ice storms)

Example of a disaster

Example of a disaster

Death and damage caused by natural hazards

• Natural hazards vary greatly in their potential to cause a catastrophe.– Floods, hurricanes, tornadoes, earthquakes,

volcanic eruptions, and large wildfires are the hazards more likely to create a catastrophe.

– Landslides have only a moderate catastrophe potential because they generally affect a small area. Drought also has a moderate potential because although it may cover a large area, there is plenty of warning time before its worst effects are felt.

– Hazards with low catastrophe potential include coastal erosion, frost, and lightning.

Death and damage caused by natural hazards

Role of History in Understanding Hazards

• A fundamental principle of understanding hazards is that they are repetitive events.

• Knowledge of historic events and recent geologic history of an area is vital to our understanding and assessment of the hazard.

• Linking the prehistoric and historic records extends our perspective of time when we study repetitive natural events.

Role of History in Understanding Hazards

• To understand the nature and extent of a natural hazard, we must study in detail its historic occurrence as well as any geologic features that it may produce or affect.

• Any prediction of the future occurrence and effects of a hazard will be more accurate if we can combine information about historic and prehistoric behaviour with a knowledge of present conditions and recent past events, including land-use changes.

Geologic Cycle• Geologic conditions and materials largely govern

the type, location, and intensity of natural processes.

• Continuous processes produce the Earth’s material, land, water and atmosphere, necessary for our survival. These processes are referred to as the geologic cycle, which is actually a group of subcycles:– The tectonic cycle– The rock cycle– The hydrologic cycle– Biogeochemical cycles

The tectonic cycle

Earth’s internal structure

The tectonic cycle

The tectonic cycle

The tectonic cycle

Plate Tectonics

The tectonic cycle

Subduction zone off Canada’s west coast

San Andreas Fault

The tectonic cycle

The rock cycle

The hydrologic cycle



Biogeochemical cycles

Fundamental concepts for understanding natural processes as hazards

1. Hazards can be predicted through scientific analysis.

2. Risk analysis is an important element of understanding the effects of hazardous processes.

3. Linkages exist among different natural hazards and between hazards and the physical environment.

4. Damage from natural disasters is increasing.5. Damage and loss of life from natural disasters

can be minimized.

1. Hazards can be predicted through scientific analysis

• Science and natural hazards• Hazardous processes are natural• Prediction and warning

Hazardous processes are natural

Prediction and warning• The effects of a hazardous event can be

reduced if it can be forecast and a warning issued. This involve:– Identifying the location of a hazard– Determining the probability that an event of a

given magnitude will occur– Identifying any precursor events, predicting the

event, and issuing a warning

Prediction and warning

2. Risk analysis is an important element of understanding the

effects of hazardous processes.• The risk of a particular event is defined as

the product of the probability of that event occurring times the consequences should it occur.

• Determining acceptable risk is complicated.

3. Linkages exist among different natural hazards and between

hazards and the physical environment.

• Linkages between natural process that are hazardous to people generally fall into two categories:– Many hazards themselves are linked– Natural hazards are linked to earth materials

4. Damage from natural disasters is increasing.

• Examples of disasters in densely populated areas

• Human population growth• Magnitude and frequency of hazardous

events

Human population growth

Population growth and the future

5. Damage and loss of life from natural disasters can be

minimized• Reactive response: impact and recovery

from disasters.– Direct and indirect effects

• Proactive response (Anticipatory response): avoiding and adjusting to hazards

Reactive response: impact and recovery from disasters

Proactive response (anticipatory)

• Proactive response: avoiding and adjusting to hazards– Land use planning– Insurance– Evacuation– Disaster preparedness– Artificial control of natural processes

Many Hazards Provide a Natural Service Function

Many Hazards Provide a Natural Service Function

Climate Change and Natural Hazards

• There is strong evidence that on a global scale Earth’s climate is now warmer than in the previous 40 years since records began

• The 1990s appear to be the warmest decade in the last 1,000 years


• Mean sea level has risen by between 10 to 20 cm from 1860 to 2000.

• Snow cover has decreased by 10% since the 1960s.

• Evidence of thawing of permafrost.


• Evidence of thawing of permafrost.


• Extreme weather events such as drought, floods, and storms are likely to become more frequent and more intense in the future.

• Since 1970s, El Niño events have increased in frequency, magnitude and duration.

Signals of Climate Change

• Global warming is projected to increase both temperature and rainfall at high latitudes and high elevations.

• Migration of species• Retreat of glaciers• Rise of sea level

Potential health impacts of climate change

• Problems associated with other global changes:– In 1997-1998, El Niño brought widespread

respiratory illnesses to Indonesia and Brazil due to haze from uncontrolled forest fires.

– After hurricane Mitch in Central America (1998), deforested areas experience flooding and landslides, and the aftermath spawning clusters of water-, insect- and rodent-borne diseases (cholera, malaria, dengue fever, and leptospirosis)

References• Natural hazards: Earth's processes as hazards,

disasters, and catastrophes – Canadian Edition. Keller, Edward A., Blodgett, Robert H., and Clague John J. Pearson Prentice Hall, 2007.

• Dangerous Earth: An introduction to geological hazards. Murck BW, Skinner BJ, and Porter SC. John Wiley & Sons Inc. N.Y. 1997.

• Life support: the environment and human health. Michael McCally. The MIT press. Cambridge, 2002.

Technology

Unit+1.+Intro+To+Nat+Hazards+Eesa05