Week 4 Flashcards
what are the 4 patterns describing how people choose to respond to a risk?
absorb, accept, reduce, change
describe the “absorb” pattern of how people choose to respond to a risk
view the risk as unproblematic or deny it outright
the probability is deemed too low to worry about
so, fate is determined by the capacity to absorb losses
describe the “accept” pattern of how people choose to respond to a risk
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
describe the “reduce” pattern of how people choose to respond to a risk
there is 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
e.g. flooding events, snow/wind related hazards
describe the “change” pattern of how people choose to respond to a risk
there is awareness of the hazard (no denial)
radical action may be taken (move away or change the land use)
what is an evocative hazard?
hazards that typically induce much public reaction despite data suggesting they may create little risk
what is an example of an evocative hazard?
pesticides
pesticide use for law care has become an issue in many communities due to increasing awareness of “potential” impacts
what are banal hazards?
hazards that induce little public reaction even tho they may have similar risks to some evocative hazards
what is an example of a banal hazard?
peanut butter has an increased risk of cancer than pesticides
in regards to risks, what is a transmitter?
generates and sends the message about the risk
in regards to risks, what is a signal?
the message itself
in regards to risks, what is a receiver?
target audience for message signals
the original signal may be considerably modified by the time it is received
in regards to risks, what is a signal value?
signals can be prescribed values by the receiver
this may be related to the characteristics of the event and/or the hazard it reflects
high signal values may suggest that a new risk has appeared or that the risk is different than previously understood
e.g. 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)
a small accident in an unfamiliar or poorly understood system (such as a nuclear power plant) may have a high signal value and cause concern sign people may perceive the risk is uncontrollable
what is stigmatization?
process by which negative images are ascribed to places, technologies, or people
the risk perception of a future event in the area could be altered simply because of past events there
describe impacts
spread of impacts
— impacts can spread like ripples and often extend well beyond the local area
— even affecting entire countries, technologies (medications), industries (meat)
secondary impacts
— property values and insurance rates may change in response to an event
what are the 5 different risk perception theories and what question do they attempt to answer?
knowledge, personality, economic, political, cultural
why do some people feel that some technologies (e.g. nuclear energy or pesticides) are a major concern while other people feel that they are not?
describe the knowledge theory for risk perception. how was it tested?
greater knowledge of fatality data leads to a greater perceived threat from the technology
tested via educational level and 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
describe the personality theory for risk perception. how was it tested?
there is consistency between personality type and the perceived threat from technological hazards
tested using validated measures and questionnaires developed by psychologists
describe the economic theory for risk perception. how was it tested?
the wealthy are more willing to take risks with technology because they may benefit more or have better access
this theory is based on the annual income of the people tested
describe the political theory for risk perception. how was it tested?
personal views toward risk are related to the political party (and policies) that the person supports
tested by determining the political ideology of the subjects thru the completion of a 20-question survey
describe the cultural theory for risk perception. how was it tested?
the worldview (the way the person believes the world operates or should operate) is correlated to how the person perceives risk
the theory is based on the way of life of a person (urban, rural, retired, child-rearing, etc)
define the hierarchical worldview
defines boundaries between superiors and subordinates
examples of this view:
— strong patriotism and support for country
— strong respect for authority (law, order, and obedience are strongly valued)
— strict ethical standards
— concern about lack of discipline in youth
define the egalitarian worldview
centres on political solutions to inequality
examples of this view:
— belief that world conflict can be eliminated with a more equal distribution of resources
— support for government efforts to reduce poverty
— support high tax burdens on the wealthy
— a lack of trust in large corporations
define the individualism worldview
emphasizes personal freedom and choice
examples of this view:
— constraints on the 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
which of the 5 different risk perception theories proved to be conclusive?
personality, political, and cultural
the cultural theory was found to be the best explanation for how people perceived the risk
describe the results for the personality theory of risk perception
those who perceived technological activities as high risk had less aggressive personality types
people with less aggressive personalities generally tend to avoid potential risks
describe the results for the political theory of risk perception
those who identified as left-wing were more likely to see the technological activities as threatening
what is a landslide?
downslope movements of rock or sediment because of gravity
movement is classified as rapid if it can be detected by eye
what are the 4 variables used to classify landslides?
mechanism of movement
type of material
amount of water present
speed of movement
what are the 3 basic mechanisms of landslide movement?
fall, slide, flow
fall
— rock or sediment dropping off the face of a cliff
slide
— downslope movement along a discrete (“straight”) failure plane
flow
— movement of particles semi-independently of one another, commonly with the aid of water
what are the types of landslide?
rock fall, slump, creep
what is a rock fall?
a type of landslide
mass movement caused by a fall mechanism
it involves rock rolling down a steep slope or falling thru the air
what is a slump?
a type of landslide
in this mass movement, the failure plane is curved upward
what is a creep?
a type of landslide
this mass movement is caused by a flow mechanism
the speed of movement ranges from a few millimeters to a meter annually
what are the forces acting on a slope (landslide)?
the stability of a slope is based on the balance between 2 types of forces
driving force
— these move material downslope; they are based on the weight of the material from vegetation, water, etc.
resisting force
— these oppose downslope movement; they are based on the shear strength of the material
what is the factor of safety?
the ratio of resisting forces to driving forces
factor of safety = RF/DF
when the ratio is over 1, the slope is stable… but when the ratio is under 1, the slope is unstable
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
what role does material type play in risk of landslides?
low consolidation and the presence of weakness of planes can increase the risk of landslides
slumps are most common in unconsolidated sediment
slumps are rotational mass movements as opposed to translational mass movements
— rotational: material falls along a curved surface
— translational: material falls along a discrete plane
translational movements often occur where sediment overlay bedrock; the failure plane is generally at the boundary between the soil and the bedrock
what role does slope play in risk of landslides?
the steeper the slope, the greater the driving force
— steepest slopes are associated with rock falls
— moderate slopes are associated with flows and slides
— gentle slopes are associated with creep
what role does topography play in risk of landslides?
topographic relief = the height of a hill/mountain above the land around it
dangerous landslides are more likely in areas of high relief!
NOTE
elevation = altitude = from sea level
relief = distance between top and base
differentiate between elevation and relief
elevation = altitude = from sea level
relief = distance between top and base
what role does climate play in risk of landslides?
the climate of an area influences the amount of water that infiltrates and erodes the soil
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
in humid climates, soil is thick, and rock is generally covered with soil and vegetation
thus, flows and creep are more likely in those areas
what role does vegetation play in risk of landslides?
dense vegetation can slow surface erosion
roots add strength and cohesion to the slope
therefore, improper deforestation often increases the frequency of landslides
what role does water play in risk of landslides?
water saturates soil increasing the likelihood of flows
following prolonged periods of deep-water infiltration, slumps can develop
water can also erode the base of slope therefore decreasing its resisting force
what regions are more at risk for landslides?
any location with significant variation in topography is at risk
describe the frank slide
it is canada’s deadliest and most well-known landslide
it occurred in Alberta
it killed 76 people, dammed the crowsnest river creating a lake, and buried 5km of railway
the exact cause of the landslide is unknown but glaciation, mining, and heavy snow are likely contributors
describe the effects of landslides
can block railways and highways in isolated areas thus severely impacting travel
as urban areas continue to expand, property damage will increase
approximately 30 people are killed by landslides annually in North America
they can result in the development of new habitats. if a landslide blocks a river from flowing, a lake will form creating a new aquatic ecosystem
produces an increase of biodiversity
landslides can carry sediments that contain valuable minerals which become concentrated at the base of a slope following an event
how do humans increase the likelihood of landslides?
grading of land surfaces for new home and building construction can increase probability of slope failure
deforestation and urbanization are currently the leading human causes for the increase in landslides
a lack of surface vegetation and a lack of tree roots enhance soil erosion
what is deforestation and how does it affect the risks of landslides?
clear-cutting and the construction of logging roads can cause landslides in geologically unstable areas
a lack of surface vegetation and a lack of tree roots enhance soil erosion
what is urbanization and how does it affect the risks of landslides?
modern engineering has allowed us to turn hilly slopes into flat land for construction
slopes are destabilized when rock is moved, laws are watered, septic systems are installed, and buildings are constructed
these can add weight to the slope increasing the driving force
how can we minimize the landslide hazard? what are features indicative of a slope?
an important first step is recognizing where they are most likely to occurs
feature indicative of unstable slopes include
— cracks on a hillside
— a recessed crest in a valley wall
— large boulders or talus at a cliff base
— tilted trees
— exposed bedrock
— an irregular land surface at a slope base
talus = fragments of rock that have moved down a slope and accumulated at its base
aerial photos are used to detect some of these features and then hazards and then hazard maps can be produced
what is talus?
fragments of rock that have moved down a slope and accumulated at its base
how can we prevent landslides?
complete prevention is impossible, but certain engineering practices can minimize the hazard
drainage control
— the objective is to remove excess water from the soil with pipes and drains
levelling the slope
— material from the upper slope can be moved to the slope base with modern technology
slope supports
— examples of these include retaining walls, rock bolts, and rock screens
how do landslide warning systems work?
tiltmeters are instruments used to detect movement along a slope
some rock screens along highways and railways in western North America are linked to signal systems
rain gauges on slopes can identify when precipitation threshold has been reached
describe the perception of the landslide hazard
the relative infrequency of large landslides tend to reduce awareness of this hazard
it is especially a concern where evidence of past events is not visible
people continue to build in areas prone to landslides
requires adjustments to minimize deaths and property damage
how can we adjust to landslide hazards?
crucial to safely cite critical facilities (e.g. hospitals, schools, power plants) away from landslide-prone areas
reducing water pressure thru good drainage is the best corrective measure against the hazard since this will decrease the driving force
analyzing landslide hazard maps and avoiding the best purchase of a home in a hazardous area is the best way to reduce risk
