circumstances. Sometimes a disaster is caused by a concurrence of several hazards. A
mudslide, for example, is often caused by a combination of soil instability and heavy rainfall. It
is then usually classified by the hazard that contributes most to the occurrence of the disaster at
that particular moment. The fore mentioned mudslide would therefore be called a climatic
event because it is the rainfall that triggers the event of the mudslide. Biologic hazards such as
epidemics of cholera or AIDS can be denominated as natural hazards (Mitchell 1999), but
because of their different nature both in appearance and consequences as in possible mitigation
methods, they will not be included in this paper.
New technologies might sometimes help us in our struggle for a safer world; modern
technology can however add new hazards in itself: man-made hazards. These new hazards
include among others radioactivity from nuclear plants, a wide range of pollutants and
hazardous substances, industrial accidents and terrorism. A distinction that can be made
between the mitigation of natural hazards and that of man-made hazards, is that mitigation of
man-made hazards generally focuses on the source of the hazard. For example, one would set
boundaries to the amount of hazardous substances that a factory may emit. For natural hazards,
mitigation usually cannot focus on the source because our technology cannot alter these natural
situations. Therefore, mitigation measures for natural hazards aim at reducing the
consequences of hazard events by making the receivers (people, buildings) less susceptible to
the hazard. A commonly used measure is for example the implementation of building codes
that have evolved in many states to reduce the consequences of earthquakes, hurricanes and/or
floods. This difference makes it clear why mitigating natural and man-made hazards requires a
distinct method of mitigation. In this paper, only natural hazards will be taken into account.
The most important natural hazards in the United States of America are earthquakes, floods,
hurricanes, wildfires and drought.
Disaster related activities can be divided into four stages: mitigation, preparedness, response
and recovery. Mitigation refers to sustained action taken to reduce or eliminate long-term
disaster risk, carried out well before the disaster event, for example building codes and zoning
regulations designed to make property less susceptible to earthquakes (Godschalk e.a. 1999,
Quarantelli 2003, Orians & Bolton 1992, FEMA 1997). All short-term activities undertaken
following a disaster warning, such as temporary property protection and evacuation, contribute
to disaster preparedness. When a disaster event occurs, the response stage begins. It consists of
temporary emergency services such as search-and-rescue operations, temporary shelters an