A natural hazard is a very difficult term to define, and there are many different theories on the subject. However they all stem from the same basic ideas, firstly that the event is natural. To define it as natural means that it is an element of the physical environment- atmospheric, hydrological, geological and wildfire phenomena. Secondly that it is a hazard, this encompasses that it is harmful to man or his property. A good definition that includes these two factors is therefore:
Those elements of the physical environment harmful to man and caused by forces extraneous to him.
However it is difficult to decide how much damage must be caused to deem the event as a hazard. A “disaster” is a term often associated with the natural hazard- however again this is a difficult term to define. A disaster may be an event which causes unacceptably large numbers of fatalities and/or overwhelming property damage. But what if the event only causes slight damage or potential damage, is this still a hazard or is it only deemed hazardous if disaster occurs.
For the event to be deemed a hazard there must also be human involvement, otherwise it is classified as a natural phenomena- a volcano erupting which causes no damage to humans, is not a hazard, it must occur within a populated area to cause havoc and disaster which defines it as a hazard. Many natural hazards although natural, may be human induced, when man has altered natures forces causing negative effect e.g. quarrying the base of a slope, causing collapse. This again confuses the issue of classification, as does a “natural hazard” stop being natural when humans are involved in it’s cause- does the cause have to be purely natural or only of the physical environment.
Humans themselves, often provoke natural hazards by interacting closely with natures forces and putting themselves at risk. This they do for their own benefit, and it works well as long as everything stays in the norm- the way we have adapted to live with it- it is when the norm is disrupted that the relationship between nature and man is interrupted. An example of this happening is the Nile. Man has decided to live on its banks to make use of the fertile soil, left by the annual floods and to use the river as irrigation. However when the flood waters are higher than expected or are higher than the “norm” chaos arises as the floods engulfs the settlements and destroys the agriculture- the people’s livelihood.
However the most important feature of the hazards is that their origin is natural, and this comes into their classification. Hazards can vary hugely in cause, size, effect, location and frequency. Traditionally they can be classified into geophysical processes:- Tectonic, geomorphologic, atmospheric and biological, however problems occur when these overlap for example when a storm may cause flooding which later leads to a landslide. However humans may also disrupt this when they become involved in the cause- for example global warming due to increased pollution may lead to more storms, and this is where the term quasi-natural hazards comes in.
The magnitude (size) of the event will greatly alter the effect the event will have on man. The higher the magnitude the more consequence it will have on man and this is why many geophysical processes have magnitude scales associated with them invented by man e.g. Richter scale for earthquakes. These are used by man to measure the physical intensity of the hazards, but also the effect it has on humans and their property. This then becomes useful in man protecting themselves as they become more aware of frequency and effect and can then strive to do something about it to try and reduce the effects. They can also look back on the results and try and find patterns to strive at predicting the events. Although humans can do little or nothing to change the incidence or intensity of most natural phenomena they have a key role in ensuring that they remain phenomena and do not turn into disasters.
Another way in which natural hazards can be classified is by duration of impact and warning time. They can either be sudden impact hazards which are short lived and usually causes many short term problems as well as long term e.g. Earthquakes causing building collapse, then economic disaster, or creeping hazards which may take weeks or months- although these give long periods of warning they can be just as disastrous in the long term e.g. drought.
Hazards also vary in spatial distribution, both geographically and in terms of their impact. Some hazards are very easily predicted within their whereabouts e.g. earthquakes will generally occur on a plate boundary, where as some such as mass movement are much less predictable. The impact also can vary spatially- this depends on the distribution of the events and the variations in vulnerability of the population.
Some areas are far more vulnerable to natural hazards not only in their magnitude and frequency but also in how economically developed they are. Vulnerability refers not only to the hazardous event itself but also to the ability to recover afterwards. Vulnerability can be economic, social, educational and environmental. Generally those people living in LEDC’s are more at risk of all of these forms of vulnerability, and this is why two earthquakes of the same magnitude may have very different effects depending on where they occur e.g. San Francisco where a quake may cause huge financial damage but nothing compared to Kobe, which suffers huge human and financial losses. Peoples wealth and technology effects how well they can protect themselves- by improving:- building standards to withstand higher stress levels in earthquakes, education to prepare people for what must be done, acceptance and adaptation, prevention and mitigation.
Certain people are more vulnerable when it comes to natural hazards:- the old, the young, the poorly as well as the poor and the less educated. But also the people living in the more crowded areas of the world are also more susceptible, with poor urban areas being most at risk- due to the high intensity population, held within poorly built houses with little knowledge of how to react and little resources to be able to react with.
In conclusion a natural hazard is a geophysical event which has the ability to cause loss of life or property; this may differ due to factors such as where the event takes place as well as the event itself. It is up to humans and their interaction with the event that decides how much of a hazard the event becomes.