the disaster occurs with a scale and intensity that requires emergency medical response.
Hazards can be characterised in 7 different ways, as follows;
- Magnitude - the size of the event (can be measured on the Richter scale, Beaufort scale)
- Frequency - how often an event occurs.
- Duration - the length of time the hazards exists (could be minutes for an earthquake or decades for a drought).
- Areal extent - the size of the area covered by the hazard (can range from small scale to continental)
- Spatial concentration - the distribution of the hazard over the globe (can be concentrated on plate boundaries, coastal locations)
- Speed of onset - the difference between the start of the event and the peak of the event.
- Regularity - some hazards may be regular (cyclones) while others may be more random (earthquakes).
The impacts of hazards can be devastating and varied but usually injury death and loss of property are the main impacts Death rates from natural hazards and disasters seems to be increasing. This is due to population growth, economic growth and the increasing use of hazardous environments.
In the 1970's and 1980's about three million people were killed by natural hazards and they affected a further 820 million people. They have also cost the global economy an estimated US $40 billion in losses and US $15 billion in relief and rehabilitation.
Natural hazards claim more lives in poorer countries with over 90% of deaths occurring in developing countries. The impact of hazards in developed countries can have a greater economic cost but may cause fewer deaths.
The effect of hazards in MEDCs will also be very different to their effect in LEDCs.
The increase in the number of deaths from natural hazards is due to several factors:
- Population growth and the use of marginal land for settlement.
- A shortage of land due to environmental deterioration.
- Economic growth creating new hazards such as chemical spills and radiation leaks.
- Technical innovations such as high rise flats and large dams.
Natural hazards are not just earthquakes and volcanoes, they can also be biological such as disease, indeed these hazards can be amongst the most devastating to property, and potentially population, for example the foot and mouth crisis that gripped Europe and the United Kingdom.
The Nile River in Egypt has been a source of life for over 5000 years. Through the times farmers have made good use of the floods. Although the flood is annual the actual timing and height of the flood is not constant. Houses where built up high to escape the majority of the flood.
They were built at least 500 meters from the banks of the river. This way they did not use up the land, which could be used for agriculture. To separate each field, small walls of earth were built. This trapped the water in the basin like field as it retreated. Small ditches were dug for drainage. In ancient times when the floodwaters were low, modern inventions were made to lift the water onto the field for irrigation.
Now they use electrical pumps to irrigate. The floods not only provide the water for the fields but also carry a new layer of silt with it. The silt settles on the ground and the floodwaters retreat leaving the silt behind. The silt is a good nutrient for the soil that will help the next crop grow. This mainly occurred in the lower reaches of the Delta.
In some areas of the Nile valley, flooding for agriculture is still used. Since the building of the Aswan High Dam, things have changed. The Dam was built to even out the flow of the Nile. Together with help of power-driven pumps, it was intended to expand the agricultural land along the Nile.
As you can see from these case studies the impact, which hazards have upon a country, is due to its economic and technological level of advancement. MEDCs will have much less trouble than LEDCs in dealing with problems as they have the technology to predict events and to deal with events once they occur.
