NA-Tech Risks from a Planner's Perspective. Scira Menoni, Dipartimento di Scienze del Territorio, Politecnico di Milano, Via Bonardi 3, 20154, Milano, Italy
SOME KEY POINTS
In the last years many governments as well as national and
international agencies have recognized that land use planning
plays a key role in risk reduction. In this paper an attempt will
be made to enlighten how planning and risk assessment procedures
can be intertwined to improve existing prevention strategies.
From a planner's perspective some assumptions that had been
explicitly or implicitly accepted in the past should be changed,
especially the belief that risk can be isolated from its
geographical context and treated like a point in the space which
can be made safer adopting only technical solutions. There are a
number of reasons why this assumption doesn't work well for land
use planning purposes.
The first is that some hazards, natural as well as
technological are not punctual, they rather cover a surface, in
the sense that the same source of potential damage cannot be
confined to one place. This is true for earthquakes but also for
infrastructures like sewage, gas and electrical systems.
Secondly risks are connected one to the other. Researchers
and decision makers usually do not consider multiple risks, as it
is already very difficult to deal with one at a time; however it
should be kept in mind that most inhabited areas are exposed to
various risks, some of which might interact in a single event
giving rise to disastrous chains. Examples of those interlaced
risks are provided by induced hazards triggered by earthquakes.
The ground shake might provoke landslides as well as accidents in
dangerous plants. However, the most common failure due to seismic
events affect lifelines. Gas leaks, which cannot be completely
avoided in wide-areas, may start fires, as it occurred after many
recent earthquakes striking metropolitan areas (Loma Prieta,
Whittier Narrow, Kobe).
The third reason is perhaps the most important and derives
from some Perrow's observations (1994). Among other components of
risk he identifies in particular the general environment and the
organizational factors. When information concerning lifelines
(for example the exact location of pipes) is not available or is
simply ignored by people producing town master plans, it usually
happens that owners receive building permits in areas where those
infrastructures already exist. This kind of problems is very
common in Italy (as some managers of the SNAM admitted during
interviews), but also elsewhere, as they are the results of:
The same lack of information may prove itself catastrophic
after an earthquake or an accident, when urgent demands are made
on emergency management agencies.
VULNERABILITY AS A MULTIDIMENSIONAL CONCEPT
With respect to land use planning and management needs, a very useful definition of risk is provided by UNDRO (Aa. Vv., 1979), where the latter is given in terms of expected damage and calculated as the combination of hazard and vulnerability. Vulnerability is a conceptual measure of how prone a system is to damage at increasing levels of hazard intensity (or at the combination of several hazards).
Adopting the vulnerability concept planners can better understand if and at which degree settlements are resistant to hazards, in terms of accessibility to some zones and to strategic buildings, in terms of distribution of public facilities and urban functions, and of the allocation of both economical and non-economical resources (Petrini, 1995).
Generally risk analysts measure the direct and material damage to people and to properties; in some cases they add to this value a coefficient which expresses the amount of indirect damage. The latter however is precisely the core of planners' concerns, not less than physical damages. Economic losses to public owned infrastructures and facilities, to industrial sites, as well as to other values, like landscape beauties and cultural heritage have also to be considered and must be equally weighed in the risk assessment.
Finally, as planning is a decision making system in which multidimensional needs have to be taken into account, in which conflicting demands must often enter into an arrangement, the idea that scientists (or politicians or both) should first evaluate what level of risk is acceptable or tolerable and let then planners translate this decision into land use plans may be misleading. It is perhaps better to suggest that risk reduction and mitigation strategies should become part of planners' goals, addressing their choice among project alternatives, facilities locations and so on.
In other words planners' task is to measure and to try reducing existing levels of vulnerability. In order to obtain this goal it can be useful to follow a general framework that has been developed in Italy addressing different kinds of vulnerabilities:
The systemic vulnerability develops its effects both during
the emergency and during the reconstruction and is not generally
confined to the core area of the disaster as it involves also
peripheral zones, if not whole regions or the nation itself (see
B. De Marchi, 1992).
An example of vulnerability assessment framework
All these vulnerabilities are weighed in the framework shown in table 1, assessing the behavior of gas systems in case of earthquakes.
As Bruegel (1994) says, it is unrealistic to carry out a risk
analysis calculating the risk of failure of any single pipe. It
is especially useless when large areas are considered, as it is
the case for planning purposes. At regional, metropolitan or even
urban scale a more conceptual approach should be enhanced,
considering average values as well as qualitative and
semiqualitative parameters, that allow nevertheless to map those
sub-areas and those network branches where the highest degree of
damage can be reasonably expected.
Gas, electricity, sewage vulnerability can produce double
effects: large areas might remain without the utilities they
provide and furthermore they can become induced hazards to the
same settlements already stricken by seismic waves. Gas leaks for
example might have important effects in the immediate aftermath
of an earthquake: they hinder and slow search and rescue
activities by causing fires that can obstruct access ways. In
addition, the more widespread the damage to the network the
larger the area where gas should be shut off, as authorities will
rather decide to interrupt major branches serving entire regions
rather than risk not being able to control every single leak.
In the framework the different vulnerabilities that have been mentioned are shown. With respect to the organizational vulnerability in particular emergency preparedness plans inside agencies and companies controlling lifelines as well as inter-organizational emergency plans are considered. In the study area consisting of the Brescia seismic municipalities, where the framework has been applied, six companies at least distribute gas at the local level: some have excellent emergency plans that work however only for failures they control directly through their staff. No plan coordinates all the companies one with the other, and with other agencies, including the Civil Protection Agency and Firemen stations.
The parameters shown in table 1. are just part of a more general scheme that has been developed to assess the global vulnerability of an entire regional area. In the latter the physical and social vulnerability as well as the vulnerability of other subsystems shaping the built environment (industrial sites, residential units and so on) are evaluated to achieve a comprehensive understanding of the regional system behavior at the earthquake impact, during the emergency and the reconstruction.
It is very important in fact to maintain multidimensional
levels in the risk analysis and assessment when regional,
metropolitan and urban are concerned: both comprehensive
frameworks and sectorial models must be developed following
interlaced paths. Frameworks and models will always represent a
simplification of reality, even a rough simplification whenever
planning is involved, which however will help identify those
vulnerable elements that can be controlled and mitigate to
achieve better results in prevention strategies.
References
Aa. Vv. (1979). Natural disasters and vulnerability
analysis. Report of expert group, Rep. UNDRO (Office of the
United Nations Disaster Relief Co-ordinator), July.
van Bruegel K. (1994). Acceptance criteria for high
consequence risks: a critical appraisal in G.I.
Schueller, M. Shinozuka, J.T.P. Yao eds., "Structural safety
& reliability." Proceedings of ICOSSAR '93 - The 6th
International Conference on Structural Safety and Reliability.
Innsbruck, Austria, 1993.
De Marchi B. (1992). Vincoli sociali dell'ambiente in:
"SistemaRicerca", n. 27, July-September.
Perrow C. (1994). The limits of safety: the
enhancement of a theory of accidents. In "Journal of
Contingencies and Crisis Management". vol. 2, n. 4,
December.
Petrini V. (forthcoming). Overview report in vulnerability
assessment. In "Proceedings of the Fifth International
Conference on Seismic Zonation", Nice, France, October 1995.