Claire Flashcards
(1) Hazard-Risk cycle
Hazard: anything that can cause harm Risk: How great the chance that someone or something will be harmed by the impact Vulnerability and resilience Exposure Value of potential loss Impact
• Risk is very complicated to calculate – essentially a calculation – effects vary on parts of society (infrastructure or welfare) and person to person (wealth, social class etc)
(1) What is a (natural) hazard?
“A dangerous natural phenomenon that may cause loss of life, property damage and disruption.”
UNISDR Terminology on Disaster Risk Reduction, United Nations, Geneva, Switzerland
(2009)
• Intensity and recurrence of hazardous events is key to the ensuing risk and impact
- An event that can cause harm
- Volcanos produce many types of hazards
(1) volcanoes pose a potentially ‘low probability–high impact’ event:
- Eruptions are unevenly spaced in time and magnitude:
- Problem of human memory – people are underprepared for the threat that they live close to - Ethiopia
- Unlike other natural hazards:
- The range of hazards is large e.g., lava, ash, flows etc.
- The hazard may continue for decades e.g., lahars
- The hazard may continue whilst the volcano is quiescent e.g., gas, lahar, landslide
- Effects continue after eruption – sometimes for years to centuries and longer – lahars that flow in rainy seasons – degassing that continues for decades
(1) Types of volcanic hazards
– Lava – Pyroclastic flow (PDC) – Ash fall / tephra – Dome collapse – Explosions / lateral blasts – Gas – Acid rain – Earthquakes – Flooding & jökulhlaup - – eruption under glacier – melts glacier and causes a torrent of water that causes flooding Secondary hazards – after or due to eruption - – can still happen at same time as hazard but is not directly related – tsunamis can cause death, but it was due to volcano – Lahar – Landslide / debris avalanche / sector collapse – Ash remobilisation – Tsunami – Evacuation – Roof collapse – Floods – Fires
(1) What is vulnerability?
“The characteristic of an element that makes it susceptible to the effects of a hazard.”
UNISDR Terminology on Disaster Risk Reduction, United Nations, Geneva, Switzerland
(2009)
• High vulnerability, and exposure, are generally the outcomes of skewed development processes
• Environmental management
• Demographic changes
• Rapid movement of people – due to commuting, war, migration, etc
• Rapid and unplanned urbanization in hazardous areas
• Failed governance
• Corruption means the scientific research does not reach the government
• Scarcity of livelihood options
• If hazard destroys crops, then farmers will be severely affected
• Related to susceptibility, fragility, weakness, lack of capacity etc
(1) What is resilience?
The capacity to cope, absorb, adapt or recover quickly from the effects of a hazard Human responses to volcanic threats are influenced by many factors which impact on societal resilience: • Culture • Belief systems – society cohesion • Education (level and about specific hazards/risks) • Awareness • Trust in experts/authority • Indigenous knowledge • Past experience • Self-reliance, mental fortitude • Good support networks • Good lifestyle – health, fitness, job • Ability to protect yourself • Preparedness
- Building design
- Urban planning
- Variety of livelihoods
- Food resources
(1) How to build resilience?
- Community resilience (and disaster prevention) can be improved through preparedness and hazard & risk mitigation:
- Disaster risk reduction – e.g., high bridges on lahar routes, location of key infrastructure away from hazardous paths
- Hazard mitigation – e.g., diverting lava
- Preparedness – e.g., community education, familiarity with potential hazards and warning systems/messages
- Emergency response measures – e.g., evacuation plans
- Sustainable livelihoods, poverty reduction, good medical facilities (‘safe hospitals’)
(1) What is exposure?
“People, property, systems and other elements present in the hazard zone that are subject to potential loss.”
UNISDR Terminology on Disaster Risk Reduction, United Nations, Geneva, Switzerland
(2009)
• If populations and resources were not located in (i.e. exposed to) potentially dangerous settings, no problem of disaster risk would exist
• Exposure is a determinant of risk but not a necessary one – i.e. it is possible to be exposed but not vulnerable.
• But, to be vulnerable, it is necessary to be exposed.
• Exposure risk relates to duration and intensity so must be assessed.
Differs from environmental concentrations because people can take protective actions to reduce their exposure (e.g. wear a facemask), whilst other actions might increase exposure locally (e.g. kids playing in ash)
(1) Exposure equation:
Intensity X Frequency x Duration
(1) Risk
- Key words: ‘chance’, ‘likelihood’, ‘probability’, ‘possibility’, ‘uncertainty’, ‘threat’
- Definitions:
- the probability that an adverse event will occur.
- the combination of the probability of an event and its negative consequences
- the likelihood that someone/ something will be harmed/lost by a hazard
- The uncertainty concerning the occurrence of loss
- Any threat which could have a positive or negative effect on an ‘objective’ or ‘element’
- A measure of the probability and severity of an adverse effect to health, persons, property or the environment.
- Effect: impact, damage, injury, liability, loss, harm
(1) Risk equations – depends on need
- Hazard probability
- Hazard probability x vulnerability
- Hazard probability x vulnerability x value of the element at risk (x exposure)
(1) The disaster risk equation:
‘The risk of disaster increases as the frequency or severity of hazards increases, people’s vulnerability increases and people’s capacity to cope with the consequences is decreased.’
• Hazard probability x vulnerability (± exposure)
Capacity to cope
(1) What is ‘impact’?
- We can also call it ‘effect’, ‘harm’ or ‘damage’
- To have a strong effect on someone or something.
- We can categorize impact in many ways:
- Primary and secondary impacts
- Acute and chronic impacts (immediate and long term)
- Proximal and distal impacts
- Cascading impacts (or ‘knock-on effects’)
(1) Impacts of volcanic hazards
• Immediate – Death – Injury – Damage to buildings – Damage to infrastructure/utilities • Roads • Water • Sewage • Electricity etc. – Damage to agriculture – Damage to aviation – Displacement of populations • Social problems • Vulnerability • Health – acute disease & epidemics • Famine – Longer term – Climate change – Chronic disease – Vegetation death
- Starvation - a secondary or even tertiary hazard
- 3 of the top 4 are secondary incidents
- Average number of fatal incidents per fatal incident is going down in time – better infrastructure – humanitarian aid – healthcare – hopefully means that 60,000 people wont starve again?
(1) Electricity infrastructure
Insulator Flashover: may occur with <3 mm of ash fall provided a significant portion of the insulator creepage distance (>50%) is covered in wet ash
Loading Damage: ash accumulation may overload lines, weak poles and light structures, and cause additional tree-fall onto lines. Precipitation will exacerbate the risk:
• Loading damage typically occurs with >100 mm ash accumulation
• Induced tree fall from ash load may occur with thicknesses >10 mm
Disruption to Control Systems: ash ingress into heating, ventilation and air-conditioning systems can block intakes leading to reduced performance, and affecting dependent systems:
(1) Relationship of damage and disruption
- Tephra (ash fall) causes little damage but huge disruption
- The remainder have a relationship
(2) Volcanic hazard assessments
• We need to answer the following questions:
– When and where did the volcano last erupt?
– How frequently has the volcano erupted in the past?
• These tell us about the return period i.e. when the volcano is likely to erupt again
– What sizes of eruptions occurred in the past?
• This tells us about possible magnitude
– What types of eruptions occurred in the past?
• This tells us about how explosive or effusive the eruption could be
– What hazards were produced and how far have they reached?
• This tells us about likely impact
– How long have eruptions lasted?
• Tells us the likely length of disruption
(2) Types of Hazard Assessment
Long-term assessment (likelihood of the future based on the past)
Short-term assessment (monitoring)
Dependent on:
• User of the assessment: civil protection, national government, international bodies e.g. UN
• Decision-making timescale
• Availability of data
The point – forecasting (not prediction)
to help to decide what to do in the future based on anticipated impacts
(2) Monitoring volcanos
• Volcano-monitoring techniques provide the data needed for issuing short-term warnings or predictions over timescales of hours, days, or perhaps weeks.
• Core methods
– Seismic
– Ground deformation
• Supportive methods
– Microgravity, electrical & magnetic studies
– Geochemical monitoring (gas and water)
– All detect and measure changes in the state of a volcano caused by magma movement beneath the volcano.
(2) Seismic monitoring
• Vital tool for monitoring and prediction
• Baseline monitoring and seismic array (multiple stations) essential
• >25 successful forecasts in 20 years
• Vital tool for monitoring and prediction
• Baseline monitoring and seismic array (multiple stations) essential
• >25 successful forecasts in 20 years
• Measure seismic waves produced by deformation through movement of gas/magma.
• Earthquake activity beneath a volcano almost always increases before an eruption
• Different types of earthquakes represent different physical processes
o e.g., harmonic tremor, fracturing, magma movement
- Volcano tectonic earthquake – cracking and fracturing
- Harmonic tremor – movement of magma up conduit
(2) Volcano deformation overview:
- Upward pressure from rising magma deforms volcano
- The ground can change shape by rising up, subsiding, tilting, or forming bulges
Taal 2020 deformation
• Usual deformation are mm scale over a few months/years
• At Taal it has been very rapid – the deformation has become a hazard itself
(2) Volcano deformation breakdown:
Tilt measurement: tiltmeter, ‘dry’ tilt
Lateral displacements: EDM (electronic distance meter), GPS
Vertical displacements: Precise leveling
Space-based: radar interferometry (InSAR), lasteraltimetray
Interferometric Synthetic Aperture Radar. Satellites record images of the Earth’s surface, and these images can be combined to show subtle movements of the ground surface, called deformation.
(2) Geochemical data
Determination of magmatic composition to gain insights into:
- Eruption style and magnitude
- Depth of magma chamber
- Rates of magma ascent
- Magmatic processes
(2) Hazard Assessment Methods
- Probabilistic / Stochastic – determine probability distributions for range of behaviours and outcomes.
- Deterministic - outcomes are precisely determined through known relationships among states and events, without any room for random variation e.g. scenario.
Probabilistic – determine all the possible outcomes
Deterministic – take one scenario and run with it
Volcanos are stochastic – but it is difficult to try to understand and plan for all outcomes
