Global Report on Human Settlements 2007 - PoA-ISS

7
CHAPTER
DISASTER RISK: CONDITIONS,
TRENDS AND IMPACTS
Disasters in urban areas are experienced when life support
systems fail in the face of pressure from external stress,
resulting in loss of life, damage to property and the undermining
of livelihoods. However, they are not natural events
or ‘acts of God’, but products of failed development. For the
majority of people at risk, loss to disaster is determined more
by processes and experiences of urban development and
governance than by the physical processes that shape natural
or human-made hazards.
This chapter presents an overview of global trends in
the incidence and impacts on cities of disasters associated
with natural and human-made hazards. In this context,
natural hazards include earthquakes, hurricanes, tsunamis,
tornadoes, landslides, floods, volcanic eruptions and
windstorms, while human-made hazards encompass explosions
and chemical releases. However, the conceptual
distinction between disasters associated with natural and
human-made hazards is increasingly becoming blurred, as
many human actions and practices, such as the construction
of human settlements in flood-prone areas or on the slopes
of active volcanoes, exacerbate human-made hazards. While
the focus here is primarily on large-scale disasters that register
direct impacts at the community level and above, the
characteristics of small-scale disasters whose impacts are
largely felt at the individual or household levels are
reviewed.
Epidemic diseases and environmental health are not
discussed herewith, nor are acts of war. This is because
while these forms of stress impact upon the built environment,
human health and political systems, the balance of
impact is different in each case. It is natural and humanmade
hazards that most frequently threaten urban
sustainability through damage to buildings and critical infrastructure.
The focus on natural and human-made disasters
also responds to global trends in increasing numbers of such
events, in people affected and made homeless by disaster,
and in the economic impacts of disaster, especially on the
poor and marginalized.
An overview of the relationships between urbanization
and disaster risk, human vulnerability and loss (or
outcome) is presented below, once key disaster terms are
defined. This is followed by a detailed discussion of the
distribution of disaster loss associated with natural and
human-made hazards worldwide and across cities. The
economic and social outcomes, or impacts, of disasters,
including the disproportionate impacts on the poor and
marginalized, the aged, the very young and women, are then
reviewed. Subsequently, factors generating urban disaster
risk and contributing to human vulnerability, including
modification of the urban environment, planning and
construction techniques, urban finance and poverty, are
examined. Finally, a regional comparison illustrates variation
in conditions, trends and impacts of urban disaster risk
globally.
DISASTER TERMINOLOGY
In addition to the terms introduced in Chapters 1 and 2,
terminology specific to disaster risk is first presented here to
identify what a disaster is and its component parts, and then
to identify elements of disaster risk management (see Box
7.1). It is important not to confuse the definition of terms
here with meanings attributed to these terms in sister disciplines.
For example, in the international development
community, ‘vulnerability’ is commonly used in reference to
economic poverty, whereas here vulnerability refers to
exposure and susceptibility to harm from natural or humanmade
hazards, also referred to as ‘risky events’ in the
conceptual framework presented in Chapter 2.
A disaster is understood here to be the outcome of a
vulnerable individual or society being hit by a human-made
or natural hazard. The vulnerability of an individual or
society is reduced through short-term coping and longerterm
adaptation that adjust human actions to minimize risk
impacts or outcomes.
Disaster management is seen as best undertaken
through a disaster risk reduction approach. Here, disaster
risk is addressed at a number of stages. Before hazards occur,
underlying physical and technological processes can be
contained through mitigation. Unfortunately, in most
societies, mitigation is not sufficient and residual hazard
remains. Reducing risk from residual hazard requires
preparedness, including education, risk assessment and early
warning and evacuation planning. Disaster response takes
place in the first hours and days after a disaster and