GEOS2111 Chap.1 Core concepts in hazard and disaster studies
Core concepts in hazard and disaster studies
Week 1 is the only week of GEOS2111 that contains no hazard. It contains the vocabulary, and the vocabulary is what the other twelve weeks are graded against. In ordinary English, hazard, risk and disaster are close enough to swap. In hazard and disaster studies they name three different objects: a process that might do harm, a probability calculated before anything happens, and an outcome declared afterwards.
The unit follows the terminology maintained by the United Nations Office for Disaster Risk Reduction, which is the language the Sendai Framework is written in and the language national agencies report against, so the definitions are not house style.
A hazard is any process, phenomenon or human activity capable of killing or injuring people, wrecking property, upsetting social and economic life, or degrading the environment, and its origin may be natural, anthropogenic or socionatural. Exposure is the people, assets and systems located where that process operates, a property of place and timing rather than of wealth or fragility.
Vulnerability is the set of physical, social, economic and environmental conditions that increase susceptibility to impacts, and the word before matters: those conditions were already there. Capacity is what a community can bring to bear, and resilience is its ability to resist, absorb, accommodate, adapt to, transform and recover, treated here as a contested concept rather than a settled good.
Risk is the probability of loss across a stated window, worked out from the hazard, what is exposed, how vulnerable it is and what capacity stands against it. Disaster is the only term in the set that names a realised outcome, and its definition is social: a serious disruption of the functioning of a community or society. Nothing about magnitude makes an event a disaster; disrupted people do.
On top of the definitions the week teaches one mechanical procedure, the risk assessment, run as four ordered questions that end in a cell on a likelihood by consequence matrix and then, if the cell is unacceptable, in a walk down the hierarchy of controls from elimination to protective equipment, with whatever survives named as residual risk.
It closes on how effects are counted, splitting direct impacts that follow immediately from the physical process from indirect impacts that follow later from the direct ones, and on the four phase prevention, preparedness, response and recovery cycle that organises disaster management.
The week also introduces an argument the field is still having, over whether the phrase natural disaster should be retired because it relocates responsibility from decisions onto weather.
What this chapter covers
- 01
Hazard as a threat: a process that may cause harm, natural, anthropogenic or socionatural in origin
- 02
Exposure: who and what is in the footprint, and why exposure is set by location and timing
- 03
Vulnerability as pre-existing condition, and social vulnerability as unequal exposure plus unequal access to resources
- 04
Capacity and resilience: what a system can bring to bear, and why resilience is a contested word
- 05
Risk as a probability with a timeframe, and the difference between acceptable and residual risk
- 06
The four questions of a risk assessment, and the likelihood by consequence matrix they end in
- 07
The hierarchy of controls: elimination, substitution, engineering, administrative, protective equipment
- 08
Disaster as a social outcome, and its neighbours emergency and crisis
- 09
Direct and indirect impacts, and why early loss figures are systematically too low
- 10
Disaster management and disaster risk reduction, and the prevention, preparedness, response and recovery cycle
- 11
The argument against the phrase natural disaster, and what it is really claiming
Placing a scenario on the matrix, then choosing controls in the right order
- +1Name the hazard precisely. It is not storms in general. It is riverine flooding of the reserve driven by upstream rainfall on a catchment that is already wet, arriving with a lag of hours after the rain falls somewhere else. The lag is part of the hazard description and it is what makes the site dangerous on a day that may look clear overhead.
- +1Identify exposure. Attendees on the reserve, vehicles parked on it, temporary structures, and the single access road, which floods before the reserve does and therefore removes the exit before it removes the site. Exposure here is created by the schedule and the site choice, not by the weather.
- +1Assign likelihood with a timeframe. The window is one specified day. Given saturated antecedent conditions and a forecast cluster over the catchment, inundation of the low road within that day is Likely rather than Possible. State the window explicitly, because the same hazard over a single afternoon and over a whole season are different bands.
- +1Assign consequence, which is where vulnerability enters. A public crowd including small children and people with limited mobility, on a site whose only exit fails first, converts shallow water into a Major consequence. The same water across an empty paddock would be Minor. Consequence is a function of who is present and how they can leave.
- +1Read the cell and act on it. Likely crossed with Major sits in the extreme band, outside any acceptable range, so the assessment must change something. Eliminate by moving the date or the venue above the flood level. If the date is fixed, substitute a site with a second exit; engineer by closing the low road and providing a marshalled alternative route; administer by setting a river-height trigger for withdrawal and briefing marshals against it; and only then rely on signage and warnings. Whatever remains is residual risk and is written into the plan rather than assumed to be zero.
Key terms
- Hazard
- A process, phenomenon or human activity with the potential to kill or injure, to harm health, to damage property, to disrupt social and economic life, or to degrade the environment. Its origin may be natural, anthropogenic or socionatural, and natural hazards are usually extremes of an ordinary process, such as too much water or too little.
- Exposure
- The people, assets, systems and activities located in a place where a hazard operates. Exposure is determined by location and timing, so an empty reserve and a crowded one carry very different exposure to identical water.
- Vulnerability
- The physical, social, economic and environmental conditions and processes that raise how susceptible a person, a community, an asset or a system is to the impacts of a hazard. The conditions are present before the event, which is why vulnerability explains losses rather than being caused by them.
- Social vulnerability
- Unequal exposure to risk combined with unequal access to the resources needed to prepare, respond and recover. It is why two households in the same street can experience the same flood as an inconvenience and as a permanent loss.
- Capacity
- The combination of strengths, attributes and resources available to a community or organisation to manage and reduce disaster risk and to cope with an event. Capacity and vulnerability are separate axes, so a system can score high on both at once.
- Resilience
- Quoted from UNDRR terminology (2017), which is the wording this unit uses: “the ability of a system, community or society exposed to hazards to resist, absorb, accommodate, adapt to, transform and recover from the effects of a hazard in a timely and efficient manner.” The unit treats it as contested, so a strong answer always says resilience for whom and to what.
- Risk
- The potential loss of life, injury, or damaged and destroyed assets that could occur to a system, society or community within a stated period, determined probabilistically from hazard, exposure, vulnerability and capacity.
- Acceptable risk
- The level of loss a society or organisation judges tolerable given existing social, economic, political and environmental conditions. It is a judgement rather than a property of the hazard, so it always needs the question of who decided and who bears the loss.
- Residual risk
- The risk that remains after controls have been applied. Naming it is a required step, because a control programme reduces risk without driving it to zero and a plan that omits it is claiming something untrue.
- Hierarchy of controls
- An ordered set of risk treatments applied strongest first: elimination, substitution, engineering controls, administrative controls, then protective equipment. Only the first removes the hazard, so the order encodes how much residual risk each choice leaves behind.
- Direct impact
- Harm that lands at once and follows straight from the physical workings of the hazard: people killed or hurt, housing destroyed, and damage to transport, public services and businesses.
- Indirect impact
- An effect appearing later because of a direct effect, such as homelessness after housing is destroyed, unemployment after workplaces are, or illness after displacement and stress. Indirect impacts accumulate over years and are the part of the ledger that early loss figures miss.
- Disaster risk reduction
- The policy objective of disaster management: preventing new disaster risk, reducing existing risk and managing residual risk, so as to strengthen resilience and contribute to sustainable development.
Core concepts in hazard and disaster studies FAQ
What is the difference between a hazard and a disaster?
A hazard is a process that may cause harm; a disaster is a realised, serious disruption of a community or society. The gap between them is filled by exposure, vulnerability and capacity. A magnitude 7 earthquake under uninhabited desert is a hazard event and nothing more, because there is nobody there for it to disrupt.
The same rupture under a dense city with unreinforced masonry housing and no functioning warning system is a catastrophe. This is not a semantic point; it is the organising claim of the whole unit and the reason Week 1 exists. It also has a practical consequence for how you write: an answer that explains losses by describing the physical event has answered only the first quarter of the question.
The examinable move is to name the hazard, then name what was exposed, then name the conditions that were already there, then weigh the capacity to warn, evacuate and recover.
How do I tell exposure and vulnerability apart in an exam answer?
Ask which one you could change by moving people, and which one would still be there if you did. Exposure is about being in the footprint: it is set by where people and assets are and when. If you evacuate the floodplain, exposure falls to near zero regardless of anything else.
Vulnerability is about the state those people and assets are already in: income, housing quality, health, age, language, tenure, insurance, social connection. Evacuating people does not make them less vulnerable; it just removes them from the hazard for a while. A quick test on any sentence you write: if the sentence would still be true a year before the event and a hundred kilometres away, it is describing vulnerability.
If it is only true because of where someone was standing that day, it is describing exposure.
What exactly is a risk matrix and how do I use one under time pressure?
It is a grid with consequence bands along one axis and likelihood bands along the other, and each cell carries a rating such as low, medium, high or extreme. You use it by making two independent judgements and then reading the intersection. The discipline is in the order: name the hazard, list exposure, assign likelihood with an explicit timeframe, assign consequence given who is exposed, and only then look at the cell.
Under time pressure the failure mode is predictable. Students form an impression of how bad the situation feels, find the cell that matches the impression, and then write justifications for both axes. That produces inflated likelihoods and consequence bands that ignore vulnerability. Write the two bands down before you look, and the matrix will do its job.
Why does the unit make a point of the phrase natural disaster?
Because the adjective does analytical work that is hard to defend. Hazards can genuinely be natural: an eruption, a rupture, a cyclone. The disaster, though, is produced where that process meets exposure and vulnerability, and both of those are the result of decisions about where people live, what they live in, what they can afford and what warnings reach them.
Calling the outcome natural quietly moves responsibility from those decisions onto the weather or the Earth. There is an active campaign in the field to retire the phrase for exactly this reason.
You are not required to agree with it, but you are expected to be able to state the argument, say what it is claiming and evaluate it, which means being able to describe a case where the framing genuinely changed who was held accountable.
Is resilience simply the opposite of vulnerability?
No, and the unit sets a discrimination question on precisely this. They are separate axes rather than two ends of one spectrum, so a system can be high on both at once. A well organised low income community may be extremely vulnerable in the sense of housing quality and financial buffer while being highly resilient in the sense of social networks, local knowledge and the ability to reorganise quickly after an event.
Conversely a wealthy suburb with good buildings can be brittle when its infrastructure fails, because it has no practice at operating without power, water or logistics. Resilience is also a contested concept in its own right, and the useful habit is to specify it: resilient for whom, to what shock, over what timescale, and at whose expense.
What counts as an indirect impact and why does it matter for the numbers?
An indirect impact is an effect that appears later because of a direct one. Housing is destroyed, so people become homeless; workplaces are destroyed, so people become unemployed; displacement and stress produce illness, and disease spreads in crowded temporary accommodation. It matters because of who counts what and when.
Direct losses are visible, countable and frequently insured, so they appear in headline figures within weeks of an event. Indirect losses accumulate over months and years, are distributed across many households and small businesses, and often have nobody with an interest in tallying them.
The result is systematic and predictable: early published loss figures understate the true cost, and the ratio of understatement is largest exactly where the population was most vulnerable to begin with.
Where do prevention, preparedness, response and recovery actually sit in time?
Very unevenly, which is the examinable part. Drawn as a wheel the four phases look like equal quarters. On a real time axis, prevention is continuous and never stops, preparedness ramps up over a season or weeks, response occupies hours to weeks around the impact, and recovery runs for months to years afterwards.
Response is by far the shortest phase and attracts nearly all the attention, the funding announcements and the photographs. When a question asks you to locate an intervention, answer with the phase and the timescale together, because that is what shows you understand the asymmetry rather than the diagram.
It also explains a recurring political pattern the unit returns to: the money is easiest to raise for the phase where it does the least good per dollar.
Exam move
Treat this chapter as the one you must be able to write from memory, because everything later is graded against it. Build a single sheet with the seven terms down one side and two columns beside each: what it names, and the boundary students cross by mistake. Then rehearse the discrimination rather than the recall, because the early feedback test is short and fast and rewards telling near neighbours apart.
Give yourself pairs and force a one sentence distinction: hazard against disaster, exposure against vulnerability, capacity against resilience, risk against consequence, emergency against crisis.
Second, drill the risk assessment until the four questions come out in order without thinking, and practise on small everyday scenarios rather than famous disasters, since the procedure is the same and the low stakes keep you honest about the timeframe. Always write the likelihood band and the consequence band before you read the cell.
Third, memorise the hierarchy of controls in order and attach one concrete example to each tier for a hazard you know well, because a question that asks for controls wants the ordering argument, not a list of good ideas. Fourth, keep a one line note of every case study the unit uses, including this week's, with the country, the date and the concept it best illustrates.
The habit costs a minute a week and it is the only reliable way to satisfy the learning outcome that asks for examples from high, middle and low income countries. Finally, when you meet a hazard in Weeks 3 to 10, come back to this sheet and run the four part move on it deliberately at least once. The chapters ahead are ten repetitions of one argument, and this is the argument.
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