Sustainability and Remediation - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 921

Box 20.1 Multi-Criteria Analysis (MCA)
A range of qualitative sustainability appraisal techniques have been published
based on scoring systems, with different levels of complexity, for example
for regional spatial strategies (Office of the Deputy Prime Minister 2005a ),
project appraisal (Ministry of Defence 2006 ).
Multi-Criteria Analysis (MCA) is often used in decision making. MCA is
a structured system for ranking alternatives and making selections and deci-
sions. Considerations used in MCA are: the magnitude of an effect (score)
and the importance (weight). MCA describes a system of assigning scores to
individual effects (e.g. impact on traffic, human health risk reduction, use of
energy, etc). These can then be combined into overall aggregates on the basis
of the perceived importance (weighting) of each score. With MCA, ranking
and decision making processes can be made very transparent (Environment
Agency 2000 ; Wrisberg et al. 2002 ).
MCA is not a tool that directly analyses physical or monetary information.
Rather it is an analytical tool at a higher level, bringing together different
considerations in a structured way. However, techniques such as CBA and Life
Cycle Assessment apply MCA principles in their use of weightings, scoring
(valuations) and aggregation, as does the sustainability appraisal described in
this guidance. MCA describes a range of techniques, and at its most complex,
MCA might include analyses of individual preferences of stakeholders for
weightings and quantitative valuations (such as LCA techniques) for deriving
scores. 20
The use of weightings is a difficult decision for an assessor to make, as there may
be strong demands for “importance” to be considered in the sustainability appraisal.
However, the impact of weighting is to skew the findings of an appraisal. Consider a
very big “impact”, which would lead to a very high score, combined with the nature
of the effect being considered to have a very high importance, which leads to a high
weighting. The combination of the score and weighting is geometric (multiplied).
However, the aggregation of individual score and weighting products is arithmetic
(added). Consequently the sustainability appraisal will be dominated by the highest
scores with greatest weightings. While this may have been the intention, the conse-
quence of these geometric products with addition may be to submerge the effect of
other factors on the sustainability appraisal to seeming irrelevance.
An alternative to using scores is to use rankings. Rankings can be evidence-based
without the limitation of attaching “values”. Rankings simply show which options
are better than others on the basis of available evidence. However, once generated
20 In this scenario MCA approaches are used both in making valuations, and combining different
valuations, for example environmental impacts and costs.