Global Report on Human Settlements 2007 - PoA-ISS

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Natural and human-made disasters
Box 8.3 Multidisciplinary assessment of urban seismic risk, Bogotá City, Colombia
The Holistic Vulnerability Index uses a novel methodology for
incorporating social as well as physical indicators of vulnerability,
and combining these with seismic hazard data to produce an
assessment of urban seismic risk. The index has been applied to 19
districts of Bogotá City in Colombia. Four variables are included in
the measurement of the physical vulnerability of buildings and
public infrastructure:
• damaged area in square kilometres;
• mortality and number of injured;
• ruptures to water mains, gas networks and power lines; and
• number of telephone exchanges and electricity substations
affected.
Hazard is measured by combining data on the propensity of each
zone for accelerating seismic energy and on soil type influencing
proneness to seismic amplification, susceptibility to liquefaction and
landslides. Social vulnerability is measured from the sum of three
compound indexes:
Exposure: population exposed, density of population exposed,
exposed areas, including built areas, industrial areas and areas under
government use (health, education, administration, etc.).
Social fragility: areas of illegal or marginal human settlement,
annual rate of mortality by natural causes, annual number of crimes
per 1000 inhabitants, and level of unsatisfied basic needs.
Resilience: number of hospital beds, number of medical professionals,
area of space available for emergency housing, number of
emergency and rescue workers, including trained volunteers, overall
development level, preparedness, and emergency planning as
appraised by a relevant city authority.
Results show the complexity and context specificity of processes
leading to seismic risk. Those districts recording the highest levels
of calculated risk included the middle-income districts of
Tesaquillo, Chapinero and Usaquen, as well as the low-income
districts of San Cristóbal, Usme and Ciudad Bolivar.
The advantage of such an approach is that it presents multiple
aspects of risk simultaneously to decision-makers. This can be a
pressure to put the social as well as the physical aspects of vulnerability
centre stage in integrated urban planning. The 2000 Urban
Master Plan for Bogotá took the results of this model into consideration.
Source: Carreño, 2007
In even the richest
countries, there is a
lack comprehensive
hazards databases
approach is the Holistic Vulnerability Index, 12 calculated only
in relation to seismic risk. It measures disaster risk as the
probability of a loss occurring as a consequence of a seismic
hazard with a defined magnitude over a given time. It
includes indicators for physical and social vulnerability, thus
demonstrating to decision-makers the need for work on both
fronts. The index has been applied to various districts of
Bogotá City (Colombia), and results were considered in the
preparation of the 2000 Urban Master Plan for Bogotá (see
Box 8.3).
Assessing human-made hazard risk
Human-made hazard risk assessments tend to be driven by a
hazards focus and employ GIS software. Vulnerability is
sometimes indicated through population distribution, which
reflects the limited availability of geo-referenced social data.
However, as has been found with urban heat shocks, social
variables affecting information flows and access to resources
will influence individual exposure and susceptibility
through, for example, variable abilities to seek timely
medical assistance.
Internet tools have the potential to greatly increase
public access to geographical hazard and social data. For
example, in the US, the Environmental Protection Agency, 13
the Department of Housing and Urban Development 14 and
the New York Public Interest Research Group host internet
resources that enable the mapping of hazardous facilities,
public projects and Brownfield sites. These become powerful
risk-mapping tools when combined with data from other
sites that provides demographic and socio-economic characteristics
of the proximate populations. 15
GIS mapping of technological/industrial hazard and
social vulnerability is faced with a number of challenges. In
even the richest countries, there is a lack of comprehensive
hazards databases. In some countries, industrial hazard is
hidden behind commercial secrecy. Where point source data
for hazards are available, modelling the geographic extent of
exposure and the characteristics of affected populations is
problematic. Developing models for hazards where there has
only been limited experience of the health consequences of
exposure is difficult. In many instances, little is known of the
long-term health effects of exposure to chemicals that can
cross generations. Advances in modelling and the use of
proxy data sources provide ways for technological improvement;
but the underlying paucity of data is much harder to
address without political will.
Participatory risk assessments
Perhaps the most extensive collection of methodologies
comes from participatory risk assessments. This includes a
variety of approaches, all drawn from the tradition of participatory
approaches. 16 Many international and national
non-governmental organizations (NGOs) have developed
participatory methodologies that aim to provide a structured
way for local actors to reflect on the hazards,
vulnerabilities and capacities influencing their lives.
Examples include the International Federation of the Red
Cross and Red Crescent’s Vulnerability and Capacity
Assessment, 17 as well as ActionAid’s Participatory
Vulnerability Analysis. 18
Impetus for promoting participatory approaches in
risk assessment has been provided by the Hyogo Framework