Natural hazards and hazard risk

What is a natural hazard?

A is a natural event that threatens people's lives or property. An earthquake in an empty desert isn't a hazard; the same earthquake under a city is.

When a hazard does serious harm to people, it becomes a disaster.

Type	Examples
, caused by the movement of the Earth's plates	Earthquakes, volcanic eruptions, tsunamis
, caused by the atmosphere	Tropical storms, droughts, heatwaves, extreme cold
Other hazards, often triggered by the two above	Floods, landslides, wildfires

Common mistake

A hazard isn't automatically a disaster. Say what makes it a threat: people, homes or businesses in the way.

Key terms

What affects hazard risk?

is the chance of being affected by a natural hazard. Three things decide how big the risk is:

The hazard itself: its nature (what type of hazard it is and how much warning it gives), its (how often it happens) and its (how big or powerful it is). A coast hit by strong tropical storms most years faces more risk than one hit by a weak storm every 50 years.
how likely people are to be harmed. Poverty, poor-quality housing, poor health and living in crowded, exposed places all make people more vulnerable.
how well people and governments can prepare and respond, with warning systems, emergency services, insurance and money to rebuild.

A simple way to remember how they fit together:

risk ≈ hazard × vulnerability ÷ capacity to cope

Remember

Risk goes up with a bigger or more frequent hazard and with vulnerability, and down with the capacity to cope. If nobody is in the way, there is no risk, however big the hazard.

Common mistake

The formula isn't a real calculation, so don't put numbers into it. Use it to explain why two places facing the same hazard have different levels of risk.

Key terms

What increases hazard risk?

More people are at risk from natural hazards than ever before. Four factors explain most of the rise:

cities are growing fast, especially in poorer countries. More people crowd into hazardous places, often in informal settlements on steep slopes or floodplains, where homes are poorly built.
Poverty: poorer people often live in weaker homes on the most dangerous land, and can't afford insurance or to rebuild. Poorer governments have less money for warning systems, defences and emergency services.
Farming: volcanic soils are very fertile, and floodplains offer flat, fertile land with water for crops. Farmers live and work in these risky places, such as rice farmers on the floodplains of Bangladesh.
Climate change: warmer seas may make tropical storms more intense, and changing rainfall may make droughts and floods more frequent or more severe. Rising sea levels increase the risk of coastal flooding.

Exam tip

When you explain why risk is increasing, link each factor to one of two effects: more people exposed to the hazard, or people less able to cope with it.

Key terms

Why do people live in hazardous areas?

If a place is dangerous, why do people stay? The reasons are usually a mix of benefits, lack of choice and low perceived risk.

Benefits

Fertile land: volcanic soils and floodplains are some of the best farmland in the world.
rivers and coasts provide water, fishing, ports and flat land to build on, so many big cities grew up there.
Jobs and services: cities in hazardous places, such as Tokyo (earthquakes) and Manila (tropical storms), offer work, schools and hospitals.
volcanic areas provide geothermal energy and attract tourists, which creates jobs.

Lack of choice

Poverty: poorer people may not be able to afford to move somewhere safer, and the cheapest land is often the most dangerous.
Home and family: people's families may have lived there for generations, and they don't want to leave their community.

Low perceived risk

Big hazards can be rare, so people may think it won't happen to them, or trust warnings, defences and strong buildings to keep them safe.

You'll look at volcanoes and earthquakes in more detail in Living with tectonic risk.

Exam tip

Give a reason, then develop it with because or so, and use a named example: "Farmers live on the slopes of Mount Etna because volcanic ash breaks down into fertile soil, so they can grow crops such as grapes and olives."

Wealth and hazard risk

The same hazard can have very different effects in places of different wealth.

In richer countries, buildings are usually built to stronger standards, warning systems and emergency services are better, and people can afford insurance. Fewer people tend to die, but the economic cost can be very high, because buildings and infrastructure are worth more.
In poorer countries, more people live in poorly built homes, often on steep slopes or in crowded cities, and there is less money to prepare or rebuild. Death tolls tend to be higher, and recovery takes longer.

You'll compare two earthquakes like this: Chile in 2010 and Nepal in 2015.

Exam practice

Plan your own answer first, then open the model answers to see what each level looks like.

4 marks · about 4 minutes

Explain how vulnerability and capacity to cope affect hazard risk.

Explain means: Give the reasons why something happens, developing each point with "because" or "so".

Level 1 (Basic)· 2/4 marks (band 1–2)

Vulnerability is how likely people are to be harmed. Capacity to cope is how well people can deal with a hazard. Poor people are more vulnerable.

Why this level: Correct definitions and one simple point, but nothing is linked to risk going up or down. To reach Level 2: say what each factor does to hazard risk, and why, using "so".

Level 2 (Clear)· 4/4 marks (band 3–4)

Hazard risk is the chance of being affected by a hazard. People who are vulnerable, such as those living in poorly built homes, are more likely to be hurt when a hazard strikes, so the risk is higher. A greater capacity to cope, such as warning systems, emergency services and insurance, means people can prepare, escape and rebuild, so the risk is lower.

Why this level: Both factors are explained and linked to risk going up or down, each with an example. That is a clear, developed answer, enough for full marks on a 4-mark question.

6 marks · about 6 minutes

Explain why people continue to live in areas at risk from natural hazards.

Explain means: Give the reasons why something happens, developing each point with "because" or "so".

Level 1 (Basic)· 2/6 marks (band 1–2)

People live near volcanoes because the soil is good for farming. Some people are too poor to move. Also they like living there.

Why this level: Two relevant reasons, but they are listed, not explained, and there's no example. "They like living there" is too vague to credit. To reach Level 2: develop each reason with "because" or "so".

Level 2 (Clear)· 4/6 marks (band 3–4)

Many people live near volcanoes because volcanic ash breaks down into fertile soil, so farmers can grow more crops. Cities on rivers and coasts offer jobs and services, so people move there even if they flood. Some people are too poor to move somewhere safer, because the cheapest land is often the most dangerous.

Why this level: Three reasons, each explained, from both benefits and lack of choice. To reach Level 3: add a named example with detail, and a third type of reason, such as low perceived risk.

Level 3 (Detailed)· 6/6 marks (band 5–6)

Many people live in hazardous areas because of the benefits. Volcanic ash breaks down into fertile soil, so on the slopes of Mount Etna in Sicily farmers grow grapes, olives and citrus fruit. Rivers and coasts provide water, trade and flat land, so big cities such as Manila grew there, offering jobs, schools and hospitals despite tropical storms. Others have little choice: poorer people may not be able to afford to move, and the cheapest land is often the most dangerous. Finally, big hazards are rare, so people may believe the risk is low, or trust warnings and strong buildings to keep them safe.

Why this level: Well-developed reasons from all three groups, benefits, lack of choice and low perceived risk, with named examples (Mount Etna, Manila). Each point explains why, so this is a detailed Level 3 answer.

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