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 sophisticated Geographic 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 sustainable development 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 and matrices (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. In developing 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. Rapid assessment techniques (Section 3.8) have been designed to cope with need for quick assessments to deal with rapid changes …