OE1-3.1 Hazard, Vulnerability & Risk

What this is and why it exists

An earthquake in an empty desert is not a disaster. It is a large event and nothing more.

That sentence contains the whole foundation of this subject. Three ideas are kept apart, and keeping them apart is what makes everything after it precise.

The vocabulary

• Hazard — the event itself, such as a tremor, a flood or a cyclone.
• Exposure — the people and things in the place the hazard reaches.
• Vulnerability — what makes those people and things susceptible to harm.
• Risk — the hazard, the exposure and the vulnerability combined.
• Capacity — the resources and abilities available to cope and recover.
• Human-induced hazard — one caused by human activity, such as an industrial accident.
• Financial resilience — the ability to fund recovery without lasting damage.

The mental model

A hazard becomes a disaster only when it meets people and what they have built. So risk is not a property of the hazard alone. It combines what may happen, who is in the way, and how badly they would be affected.

That has a consequence the field is built on. You cannot reduce the hazard. You can reduce exposure by not building in the path, and you can reduce vulnerability by building differently and preparing better. Disasters are therefore substantially constructed by human decisions about where and how we build, which is a strong statement and a well supported one.

Grouping hazards by cause helps, because the measures against each group are similar. Geological hazards such as tremors and landslides. Water-related hazards such as floods, cyclones and storm surges. Pandemics, which are here because recent experience made their absence from older syllabuses conspicuous. And human-induced hazards, from industrial accidents to fires to structural collapse.

Impacts on natural systems are the part usually left out, and they matter because they feed forward. A flood that destroys mangroves removes the buffer that would have reduced the next storm surge. Deforestation on a slope makes the next heavy rain a landslide. Damage to the natural systems that absorb a hazard increases the risk from the following one, so the events are not independent.

Harm to people comes in three kinds and two of them are invisible immediately.

Physical harm is counted, reported and responded to. Psychological harm outlasts it by years, and it is routinely under-resourced because it is not visible in an aerial photograph. Social harm is the disruption of the arrangements people depend on: livelihoods, schooling, the networks that would ordinarily help them. Those two shape recovery long after the physical damage is repaired.

Financial resilience asks who bears the cost and how quickly recovery can be funded. A household with savings, a state with reserves and an insured business recover on very different timescales from those without. The speed of funding often matters more than the total, because delay converts a recoverable loss into a permanent one.

The vulnerability profile makes the subject concrete for anyone living in the country. Exposure differs completely by region. The Himalayan belt faces seismic hazard and landslides. The long coastline faces cyclones and storm surges. The major river plains flood. Parts of the west face drought. Seismic zoning maps divide the country by expected ground shaking, and a building standard that is adequate in one zone is not in another.

That is the item to learn by region rather than in general, because the right question is what your region actually faces.

What you should now be able to explain or do

Separate hazard, exposure, vulnerability and risk, and say which of them can be reduced. Explain why disasters are substantially constructed by human decisions. Group hazards by cause and say why the grouping is useful. Explain how damage to natural systems raises the risk from the next event. Name the three kinds of harm and say why two are neglected.

Check yourself