AQA GCSE Geography

What a natural hazard is

A natural hazard is a natural event that threatens people and property. The event itself is only a hazard when people or their buildings are in its way: an earthquake in an uninhabited part of Antarctica is a natural event, while the same earthquake under a city is a hazard. The harm a hazard does depends on where it happens, how strong it is and how well the people there are prepared.

Types of natural hazard

Natural hazards fall into groups according to the process behind them.

Some hazards trigger others. An earthquake under the sea can cause a tsunami, an earthquake on land can cause landslides, and a tropical storm brings both flooding from rainfall and a storm surge along the coast. These secondary hazards often do as much harm as the original event.

Factors that affect hazard risk

Risk is the chance that a hazard will cause harm to people and property in a particular place. Some factors raise the risk and others lower it, which is why identical hazards produce very different outcomes in different countries.

Factors that raise risk

• Urbanisation: More people living in cities means more people and buildings exposed in one place. Rapid urban growth in poorer countries often produces poorly built housing on unsafe land, such as steep slopes or flood plains.
• Poverty: People with low incomes often cannot afford earthquake-resistant buildings, insurance or a home away from a hazardous area. They may also depend on farmland close to a volcano or a river, so they stay where the risk is highest.
• Population density and growth: A larger population in a hazard zone raises the number of people who can be affected.
• Land use: Building on flood plains, removing trees from hillsides and draining wetlands all make floods and landslides more likely or more damaging.
• Climate change: Warmer seas provide more energy for tropical storms, and rising sea levels make coastal flooding more likely.
• Weak governance: Where building rules are not enforced, or there is no monitoring or warning system, the same hazard kills more people.

Factors that lower risk

• Monitoring and prediction: Scientists can measure changes before some hazards strike, which gives people time to leave.
• Protection: Buildings designed to resist shaking, sea walls and flood barriers reduce damage.
• Planning and preparation: Evacuation routes, drills, emergency supplies and land-use zoning reduce casualties and help the recovery.
• Wealth and capacity to cope: A richer country can pay for emergency services, rebuilding and insurance payouts more quickly.

The hazard itself

The nature of the event also matters. A hazard of high magnitude, one that strikes without warning, lasts a long time, covers a wide area or happens often will generally cause more harm than a small, slow-onset or rare one. Even so, a moderate earthquake in a poor, densely populated area can kill more people than a much stronger one in a wealthy, sparsely populated region, because vulnerability is decided by people as well as by physical strength.