Natural disasters are the products of natural variation in society.
Looking at the nature in this perspective that we can understand
a serious characters of natural disaster—the disaster system,
the dual natural of disasters, the degree of disaster and disaster chain.
The disaster system
From the mechanism of disaster formation, all the disasters
are determined by two factors, that is society and nature.
On the one hand, the combination of these two factors lead to
natural disaster, and the natural disaster have an impact on
society such as destroying buildings and affecting people's life and
property, then it may also causes accidents, public health events and
social security. The influence of natural disaster act on natural environment
is the change of landscape, hydrology and ecology. On the other hand,
the combination of these two factors also leads to man-made disaster,
man-made disasters caused disaster effect by affecting social and natural,
and in return, the disaster effect caused disaster to social and nature.
So we must have a comprehensive research on the two factors,
only in this way, we can have a deep understanding the accumulation,
occurrence, development and distribution of natural disasters.
The dual natural of disasters
Natural disasters are the products of natural variation
which endanger people's life, health, property, social function,
resource and environment.
Natural disasters have both natural and social attributes and
the natural disasters are based on the natural variation but only
the natural events which affected people’s life, property, social function
and resource environment can be called natural disaster.
The degree of natural disasters is determined by two basic factors,
the change degree of the disaster factors and the degree of the social
vulnerability, including the population, the economic density and
the ability to defend and withstand in disaster area. For example,
the loss of an 8 degree earthquake in mountains without a person or
a rainstorm in scantly populated regions is less than the same disaster
occurred in the east of China.
The degree of disaster and catastrophes
There are four different degrees to classify disasters,
those are catastrophe, big disaster, middle disaster and small disaster.
Catastrophe is classified by anyone of following three indicators-the dead
and missing people up to 1000, the affected people more than 10,000,000
or the direct economy loss more than 1000 billion. The indicators of next
three degree are falling step by step.
- Key points:Catastrophes refer to the disasters burst out in suddenly
on the bases of enough energy accumulation and bring serious effect
to people and society.
Human can’t resist catastrophes at present. There are some reasons.
The first one is the severity of the catastrophes. Catastrophes can
cause thousands of people death, more people and an extensive area
affected, leads to various secondary disasters. And then is the
comprehensiveness destruction which has an all-around impact to
the disaster area. It may hinder the development of economy and society,
influence the social security and leave psychological distress to
the disaster area. The last reason is the unexpectedness of the disasters.
Catastrophes always happened in a very short time that you have no prepare for it.
When natural variation occurs, it can affect other natural systems
with powerful forces then change the equilibrium state and lead
all kinds of natural disasters. If natural disasters act on human
engineering system with powerful forces, it will also trigger a serious
of secondary disasters and form a complex system of disaster chain.
There are three systems of catastrophe chain according to the statistical
analysis of natural disasters.
1. typhoon-rainstorm-flooding-landslide-dam break-inundation
2. earthquake-landslide-tsunami-secondary disasters
3. drought-wind storm- fine sand in the air-sizzling-chronic water shortage
The formation of three catastrophe chain could cause continuous and multiple disasters outbreak intensively, which will extend the scope of disaster hazard and aggravate disaster losses.