Natural hazards

Hazards, which can lead to disasters, can emerge from anywhere but many originate as a result of our natural environment.

Natural hazards are defined by UNDRR as:

Natural processes or phenomena that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage.

(UNDRR 2016)

There are numerous types of natural hazards usually classified as:

Hydrometeorological (climatological)

These are weather related and can be directly associated with the weather event or occur as a result of weather events. They include:

Symbol to show storm Symbol to show drought Symbol to show flooding
Symbol to show tides Symbol to show wind Symbol to show extreme heat or cold
Symbol to show snow Symbol to show Frost Symbol to show Lightning

Extreme weather events often match the hazards associated with typical weather systems but are usually considered more severe and an outlier in their frequency. For example, flash flooding caused by extreme rainfall will have many of the same outcomes of an average flood but either on a wider scale or with a more severe impact.

Geophysical

These are related to the physical processes within our planet, these hazards are often difficult to predict and can produce both slow and rapid onset events. They include:

Symbol to show earthquakes Symbol to show landslides Symbol to show volcanic activity

In the chart shown in the figure below you can see that hydrometeorological events dominate as natural hazards that result in disasters. It is interesting to note that the frequency of each disaster type does not correlate entirely with the number of people affected, as you can see in the second part of the figure. We should also note that there is no simple correlation with the number of deaths caused by each disaster type.

Image showing Number and percentage of different types of disaster between 1998 and 2017. There were 3,148 floods or 43.4%, 2849 storms or 28.2%, 563 earthquakes or 7.8%, 405 cases of extreme temperature or 5.6%, 378 landslides or 5.2%, 347 droughts, or 4.8%, 254 wildfires or 3.5%, 99 Volcanic eruptions or 1.4% and 12 dry mass movements or 0.2%. The is compared to the number of people affected where there were 2.0 billion people affected by flooding or 45%, 1.5 billion affected by drought or 33%, 726 million affected by storms or 16%, 125 million affected by earthquakes or 3%, 97 million affected by extreme temperature or 2%, 6.2 million affected by volcanic activity and wildfires or 0.1% for each, 6.2 million affected by dry mass movement or 0.1% and 4.8 million affected by landslides or 0.1%.

Select image for enlarged view

Natural hazards can be characterised by their magnitude, speed of onset, duration, and spatial extent. Larger and usually rarer events tend to have the most impact.

Biological hazards

Several disaster databases also include biological hazards within ‘natural hazards’. Such triggering events would include:

Symbol to show human and animal diseases Symbol to show oceanic microorganisms Symbol to show viruses
Symbol to show biological toxins Symbol to show spores and fungi Symbol to show invasive species, pests and plants

Your task

Consider your country, what natural hazards have occurred there?

Which are the most and least frequent hazards and which type has had the greatest impact?


References

UNISDR, (2016) Report of the open-ended intergovernmental expert working group on indicators and terminology relating to disaster risk reduction. Seventy-first session Agenda item 19 (c) Sustainable development: disaster risk reduction [online] available from https://www.preventionweb.net/files/50683_oiewgreportenglish.pdf [18 October 2019]

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This article is from the free online course:

Disaster Risk Reduction: An Introduction

Coventry University