Week 4: Risk and Culture; Landslides

Patterns of Choice

There are 4 patterns describing how people choose to respond to a risk.

Pattern 1: Absorb

1. **Absorb**
* view the risk as unproblematic or deny it outright
* the probability is deemed too low to worry about
* fate is determined by the capacity to absorb less

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Example: San Andreas fault

Pattern 2: Accept

2. **Accept**
* there is awareness of the hazard (no denial)
* passive attitude (there is little that can be done to reduce the impacts)
* hazards are often viewed as acts of God

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Example: Nigeria drought

Patterns 3: Reduce

3. **Reduce**
* awareness of the hazard (no denial)
* action is taken to reduce impacts
* typically, there is reactive response and some preparation
* usually people stay in place

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Example: Flooding events, snow and wind related hazards

Pattern 4: Change

4. **Change**
* there is awareness of the hazard (no denial)
* radical action may be taken (move away or change land use)

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Example: Australia drought

Social amplification of risk

After many years of research on public responses to risk, no comprehensive theory exists to explain why apparently minor risk events (as assessed by experts) sometimes produce massive public reactions.

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example of a hazard that typically evokes massive public reactions that are more severe than what the hazard likely warrants?

* could literally be any hazard, nuclear meltdown

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Potentially negative impacts of such reactions

* slowed down growth of nuclear industry

Evocative Hazards

These are hazards that typically induce much public reaction despite data suggesting they may create little risk

\- Ex: pesticides

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Canadians take pride in having attractive lawns around their homes and many use lawn care products to maintain them.

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However, pesticide use for lawn care has become an issue in many communities across Canada due to increasing awareness of the *potential* impact.

Banal Hazards

These are hazards that induce little public reaction even though they may have similar risks to some evocative hazards

\- ex.

According to a Consumers Union study, eating peanut butter (which contains an average level of 2 parts per billion of aflatoxin) once every 10 days presents a cancer risk of 7 in one million.  Small as that may seem, it is higher than the estimated risk of cancer from most pesticides.

* cancer risk is higher than the banned pesticides - it doesn’t make sense

Amplification of risk

* Involves hazards that have low probability as assessed by experts
* Elicit __strong public concern__

Attenuation of risk

* Involves hazards that may have greater impacts and a relatively higher probability
* Elicit __weaker public concern__

Transmitter, signal and receiver

**Transmitter**

* generates and sends the message about the risk

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**Signal**

* the message itself

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**Receiver**

* the target audience for message signals
* The original signal may be considerably modified by the time it reaches the receiver

Signal Value

Signals can be prescribed values by the receiver.

* this is related to the characteristics of the event and the hazard it reflects

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High signal values may suggest that a new risk has appeared or that the risk is different than previously understood.

eg.

Signal Value examples

A large accident that takes many lives may have a low signal value if it occurs as part of a familiar and understood system (such as a car crash).

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A small accident in an unfamiliar or poorly understood system (nuclear power plant, laboratory) , may have a high signal value and cause concern since people may perceive risk is __**uncontrollable**__

Stigmatization

This is a process by which negative images are ascribed to places, technologies, or people.

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The risk perception of a future event in the area could be altered simply because of past event there.

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Example: Love Canal - Niagara Falls Spill, US

(completely cleaned up now, but the stigma is still there)

Spread of impacts

Impacts can spread like ripples and often extend well beyond the local area

* entire countries, technologies (medications), industries can be affected (meat)

Secondary Impacts

* property values and insurance rates may change in response to an event

Risk perception Theories

Research Question:
Why do some people feel that some technologies (e.g., nuclear energy or chemical pesticides) are a major concern while other people feel that they are not a concern?

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**There are 5 theories that attempt to explain this:**

* knowledge
* personality
* economic
* political
* cultural

Knowledge theory

How was this theory tested?

* education level
* self-reported knowledge

(People were asked to provide an estimate of annual fatalities from 8 technologies (aviation, nuclear energy, lawn mowers, etc)).

Their answers were then compared to actual fatality data.

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**Hypothesis:**

* Greater knowledge of fatality data leads to a greater perceived threat from the technology

Personality theory

This theory was tested using validated measures and questionnaires developed by psychologists.

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**Hypothesis:**

* there is a consistency between the personality type and the perceived threat from technological hazards

Economic theory

This theory is based on the annual income of the people tested

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**Hypotheses:**

* the wealthy are more willing to take risks with technology because they may benefit more or have better access

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The poor are less willing because they may deal with any associated burdens (pollution).

Political theory

This theory was tested by determining the political ideology of the subjects (through completion of a 20-question survey).

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**Hypothesis:**

* personal views toward risk are related to the political party and policies) that people support

Cultural theory

This theory is based on the way of life of the people (urban, rural, retired, child-rearing, etc)

* It is supported by personal worldviews (i.e., the way the person believes the world operates or should operate).

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examples:

* Hierarchal
* egalitarian
* Individualist

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Hypothesis: The worldview is correlated to how the person perceives risk.

Hierarchical worldview

This view ^^defines boundaries between superiors and subordinates.^^

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Examples of this view:

* strong patriotism
* support for country, right or wrong
* strong respect for authority (law, order and obedience are strongly valued)
* strict ethical standards
* concern about lack of obedience in youth

Egalitarian worldview

This view ^^centres on political solutions to inequality^^.

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Examples of this view:

* belief that world conflict can be eliminated with a more equal distribution of resources
* support for gov’t efforts to reduce poverty
* support for high tax burdens on the wealthy
* a lack of trust in large corporations

Individualism worldview

This worldview ^^emphasizes personal freedom and choice.^^

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Examples of this view:

* constraints on individuals should be minimized (lack of support for heavy government regulation)
* belief that a welfare state destroys individual initiative
* continued economic growth and private profit are keys to quality of life

Study results

Tests of the 5 theories were performed in a study by Wildavsky and Dake; 134 people participated in the study.

Results: Knowledge theory

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The results suggested that greater knowledge resulted in a greater perceived benefit from technological activities, but __**results were not statistically significant.**__

rejected hypothesis

Results: Personality theory

Those who perceived technological activities as high risk had less aggressive personality types.

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People with less aggressive personalities generally tend to avoid potential risk

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__**hypothesis is true**__

Results: Economic theory

__**The results were inconsistent**__ since there was little correlation between income and personal views toward the risks of technological activities.

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Results: Political Theory

Those who identified as left-wing were more likely to see the technological activities as threatening

Results: Cultural theory

Only the highest correlations are listed on the table and all those listed are statistically significant.

Summary of results

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which theory was the best explanation for perceived risk?

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**Theory** **Result**

Knowledge → Inconclusive

Personality → Conclusive

Economic → Inconclusive

Political → Conclusive

Cultural → Conclusive

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The cultural theory was found to be the best explanation for how people perceived risk

World views and social conflict

The clash of worldviews can sometimes result in conflict whether the views are based on fact or not

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Example:

* A wealth of scientific evidence shows warming average temperatures worldwide.

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Environmentalists respond by lobbying governments to regulate emissions, but economic growth advocates cast doubt on the quality of the data

Landslides

**Definition:**

* downslope movements of rock or sediment as a result of gravity

Movement is classified as rapid if it can be detected by eye.

Classification of landslides

based on 4 variables:

* mechanism of movement
* type of material
* amount of water present
* speed of movement

3 basic mechanisms of movement

__**Fall**__

* Rock or sediment dropping off the face of a cliff

__**Slide**__

* downslope movement along a discrete failure plane

__**Flow**__

* Movement of particles semi-independently of one another, commonly with the aid of water

types of landslides

Rock fall

This mass movement is caused by a fall mechanism.

* it involves rock rolling down a steep slope or falling through the air

Slump

In this mass movement, the failure plane is **curved upward.**

Creep

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caused by what mechanism?

This mass movement is caused by a flow mechanism.

* speed of movement ranges from a few millimeters to a metre annually

The 2 types of forces on slopes

The stability of a slope is based on the balance between two types of forces:

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__**Driving Forces**__

* these move material downslope; they are based on the weight of the material from vegetation, water, etc 

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__**Resisting Forces**__

* These oppose downslope movement; they are based on the shear strength of the material.

Factor of safety

Definition:

* the ratio of resisting to driving forces
* when the ratio is **over** 1, the slope is **stable**
* When the ratio is **under** 1, the slope is **unstable**

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* If the factor of safety equals 1, resisting forces equal the driving forces.
* The forces are determined by relationships among material type, slope and topography, climate, vegetation, and water.

Role of material type

The degree of consolidation and the presence of weakness planes can increase the risk of landslides.

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Slumps are most common in unconsolidated sediment

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Translational movements often occur where sediment overlays bedrock; the failure plane is generally at the boundary between the soil and the bedrock.

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Slumps are *______* mass movements as opposed to ________mass movements.

rotational

translational

Role of slope and topogrophy:

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The ______ the slope, the greater the driving force

steeper

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slopes and the landslide type

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STEEPEST slopes are associated with rock falls

MODERATE slopes are associated with flows

GENTLE slopes are associated with creep

Topographic relief

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The height of a hill or mountain above the land around it

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Dangerous landslides are more likely in areas of high relief.

How to find relief

If the peak of a mountain 2750 metres in elevation and its base is 1550 metres in elevation, what is the relief of the mountain in metres?

answer = 1200

2750-1550

Role of Climate

The climate of an area influences the amount of water that infiltrates and erodes the soil.

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* in dry climates, vegetation is sparse, soil is thin and bare rock is exposed in many areas
* rock falls are more likely in those areas

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In humid climates, soil is thick, and rock is generally covered with soil and vegetation.

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Thus, flows and creep are more likely in those areas.

Role of Vegetation

Dense vegetation can slow surface erosion.

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How?

* roots add strength and cohesion to the slope
* therefore improper deforestation often increases the frequency of landslides

Role of water

Water saturates soil increasing the likelihood of flows.

* following long periods of deep-water infiltration, slumps can develop

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Water can also erode the base of a slope therefore decreasing its resisting force.

Regions at risk

* Any location with significant variation in topography is at risk
* BC is most at risk in Canada

The Frank Slide

Canada’s most well-known landslide

* It occurred in 1903 on Turtle Mountain near Frank, Alberta.
* The landslide killed 76 people,
* dammed the Crowsnest River creating a lake,
* and buried 5km of railway

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The exact cause of the landslide is unknown but glaciation, mining, and heavy snow are likely contributors.

Effects of landslides

Approximately 30 people killed by landslides annually in North America

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Landslides can block railways and highways in isolated areas thus severely impacting travel.

* As urban areas continue to grow, property damage will increase.

Natural service functions (benefits)

Landslides can result in the development of new habitats in forests and aquatic ecosystems.

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This produces an increase of biodiversity.

* Frank slide produced lake → more biodiversity

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Landslides an carry sediments that contain valuable minerals which become concentrated at the base of the slope following an event

Human interaction with landslides

Grading of land surfaces for new home and building construction can increase probability of slope failure.

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Timber harvesting and urbanization are currently the leading human causes for the increase of landslides

Timber harvesting

Clear-cutting and the construction of logging roads can cause landslides in geologically unstable areas.

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A lack of surface vegetation and a lack of tree roots enhances soil erosion

Urbanization

Modern engineering has allowed us to turn hilly slopes into flat land for construction.

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Slopes are **destabilized** when rock is removed, lawns are watered, septic systems are installed, and buildings are constructed.

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All of these add weight to the slope increasing the driving forc

Minimizing the landslide hazard

An important first step is recognizing where they are most likely to occur.

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Features indicative of unstable slopes include:

* cracks on a hillside
* recessed crest of a valley wall
* large boulders or talus at a cliff base
* tilted trees
* exposed rock (should have soil on it)
* an irregular land surface at a slope base

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Aerial photos are used to detect some of these features and then hazard maps can be produced.

talus

Fragments of rock that have moved down a slope and accumulated at its base

Prevention of landslides

Complete prevention is impossible but certain engineering practices can minimize the hazard:

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__**Drainage Control**__

* The objective is to remove excess water from the soil by pipes and drains

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__**Levelling the slope**__

* Material from the upper slope can be moved to the slope base with modern technology

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__**Slope supports**__

* Examples of these include retaining walls, rock bolts, and metal screens.

Landslide Warning systems

**Tiltmeters**

instruments used to detect movement along a slope.

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**Rock fences**

Some rock fences along railways are linked in Western North America are linked to signal systems

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**Rain gauges**

Rain gauges on slopes can identify when a precipitation threshold ha been reached

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Perception of the landslide hazard

The relative infrequency of large landslides tends to reduce awareness of this hazard.

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It is especially a concern where evidence of past events is not visible

People continue to build in areas prone to landslides

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This requires adjustments in order to minimize deaths and property damage.

Adjustments to the landslide hazard

It is crucial to safely cite critical facilities (hospitals, schools, power plants, etc) away from landslide-prone areas.

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Reducing water pressure by way of good drainage is the best corrective measure to counter the hazard since this will decrease the driving force

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Analyzing landslide hazard maps and avoiding the purchase of a home in a hazardous area is the best way to reduce risk.