Understanding Hazard in Disaster Management

A Hazard is a threat and future source of danger and has potential to cause harm to man, human activities, properties and environment in future.  The earthquakes, volcanic eruptions, cyclones, floods, landslides, accidents and other such events are examples of natural or manmade hazards.  The hazards represent the “potential” to harm rather than the “harm” itself. They remain hazards until they really lead to the harms. Once they cause injury or loss of human / animal lives, damage to property, disruption in socio-economic activities or environmental degradations; they become disasters.

How a Hazard turns into Disaster?

• The environmental events themselves are no hazard. The environmental events become hazards once they threaten to affect society and/or the environment adversely. For instance, a volcanic eruption which does not affect human beings is a natural phenomenon but not a natural hazard. If the same volcanic eruption occurs in a populated area, it becomes a hazard.
• When a hazardous event causes unacceptably large numbers of fatalities and/or overwhelming property damage; it becomes a disaster. In areas where there are no human interests, natural phenomena do not constitute hazards nor do they result in disasters.

Risk from Hazards

Risk refers to the measure of the expected losses due to a hazard event. The level of risk depends upon the nature of the hazard, vulnerability of the people/ area, economic value of the affected elements etc.  An area or community is said to be at risk when it is exposed to the hazards and is likely to be adversely affected by these hazards.

Types of Hazards

Hewitt and Burton (1971) classified the hazards into the following five heads viz. Atmospheric (Single element), Atmospheric (Combined elements / events), Hydrologic, Geologic, Biologic and Technologic.

Impact of Human Activities on Hazards

There are two sides of the coin. On one side, the human activities can cause or aggravate the destructive effects of natural phenomena. On the other side, the human activities can also eliminate or reduce the destructive effects. The humans can do little as far as intensity of most natural phenomena is concerned. However, humans have an important role to play in ensuring that the natural events don’t turn to natural disasters on their own. The human activities can increase the frequency and severity of the natural hazards. For instance, removing the toe of a landslide may result in movement of earth and burying that settlement. Similarly, the human settlements nearby a volcano to make use of fertile lava soil are hazardous. Similarly, destruction of the forests has led to desertification, which by its very definition is called a manmade natural (or quasi-natural) hazard.

Immutable Events

For some types of hazards the actual dimensions of the occurrence may be altered if appropriate measures are taken; these are called controllable events. For others, no known technology can effectively alter the occurrence itself. Such events are called immutable events. For example, construction of levees on both sides of a stream can reduce the extent of inundations, but nothing can moderate the ground shaking produced by an earthquake.

Primary and Secondary Hazards

The secondary hazards follow as a result of other (primary) hazard events. For instance, the Hazards secondary to an earthquake include building collapse, dam failure, Fire, Hazardous material spill, landslide, soil liquefaction, Tsunami etc.

Chronic hazards

Chronic hazards refer to a group of hazards that do not stem from one event but arise from continuous conditions (e.g., famine, resource degradation, pollution, and large-scale toxic contamination), which accumulate over time.