Metodos de eia

Chapter 3: Methodology of EIA EIA for Developing Countries
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3.0 Methods for Environmental Impact Assessment
Changes in the practice of Environmental Impact Assessment (EIA) and advances in information
technology have greatly expanded the range of tools available to the EIA practitioner. For example, map overlay
methods, originally pioneered by McHarg (1971), have evolved into sophisticatedGeographic Information
Systems (GIS). Expert systems, a branch of artificial intelligence, have been developed to help in screening,
scoping, developing terms of reference (TOR), and conducting preliminary assessments. These systems use
comprehensive checklists, matrices, and networks in combination with hundreds of impact rules developed by
EIA experts. The global embrace of sustainabledevelopment has made the analysis of costs and benefits an
integral part of EIA. This has forced the expansion of factors to be considered in traditional cost benefit analysis.
The following chapters describe some of these more specialized approaches and methods that have evolved to
meet the changing needs of EIA: 1) predictive methods (Chapter 4); 2) environmental risk assessment
(Chapter 5); 3)economic analysis (Chapter 6); and expert systems (Chapter 8).
This chapter describes some of the simplest techniques and methods for EIA, and gives information to
help choose the most appropriate method for a given situation. Ad hoc methods (section 3.1) are useful when time
constraints and lack of information require that the EIA must rely exclusively on expert opinion. Checklists andmatrices (section 3.2) are good tools for organizing and presenting information. Sectoral guidelines are becoming
widely accepted as an appropriate technique for conducting initial environmental analysis. Section 3.3 presents an
overview of the sectoral guidelines developed by the Asian Development Bank (ADB), the World Bank, and the
Economic and Social Commission for Asia and the Pacific (ESCAP).The systematic sequential approach (SSA)
(Section 3.4) provides a proven approach to “thinking through” the causal chain: activity - changes - impacts -
mitigation. Networks (Section 3.5) are a formalized way of representing these causal chains. Simulation modeling
workshops (Section 3.6) are techniques for taking network representation of impacts and building simple
conceptual models. Indeveloping the simulation models, the conceptual models are translated into mathematical
and computer language. Through the use of dynamic simulation, the impacts over time can be projected. Spatial
analysis methods (Section 3.7) allow for the presentation of the spatial pattern of environmental impacts through
map overlays. GIS is routinely used for analyzing and displaying spatial impacts. Rapidassessment techniques
(Section 3.8) have been designed to cope with need for quick assessments to deal with rapid changes in many
parts of the developing world.
The Role of Expert Judgement
Most methods and techniques for identifying, measuring, and assessing impacts rely on expert judgement.
In fact, many checklists, matrices, and models used in EIA represent decades of experience accumulatedby
numerous experts. The experts themselves are heavily involved in all aspects of the assessment — they are used
to help identify the potential for significant impacts, plan data collection and monitoring programs, provide their
judgement on the level of significance for specific impacts, and suggest ways of reducing or preventing impacts.
Choosing a Method
EIA methods range from simple tocomplex, requiring different kinds of data, different data formats, and
varying levels of expertise and technological sophistication for their interpretation. The analyses they produce have
differing levels of precision and certainty. All of these factors should be considered when selecting a method.
December 1997
EIA for Developing Countries Chapter 3: Methodology of EIA
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The EIA...