Methodology for Environmental Impacts Assessment (EIA)

The overall objectives of the EIA methodologies include the following but are not limited to: 1) Understand the nature and location of the project and possible alternatives; 2) Identify factors of analysis and assessment objectives; 3) Preliminary identification of impacts and scoping; 4) Baseline studies and evolution in the absence of projects; 5) Prediction and assessment of impacts and alternatives comparison; 6)Mitigation; and 7) Monitoring and Impacts management.

It is imperative for the EIA practitioners to consider the suitable method for conducting the assessment of the impacts of the proposed development activities. In general, the method of EIA should be easily understood and adopted, be applied within certain constraints such as a limit in manpower time and budget, and be open for further modification if it deems necessary. The choice of the EIA method needs to ensure compliance with certain regulations, comprehensiveness, and distinguishment for the overall identification, measurement, interpretation, evaluation, and communication of the impacts. In addition, the EIA method should allow the EIA practitioners to organize a large mass of heterogeneous data, summarize the data, aggregate the data into smaller sets with the least loss of information, and display the raw data and the derived information in a direct and relevant fashion considering the relevant target audience.

There are some common methods for identifying the impacts such as 1) checklist; 2) matrices; 3) networks; and 4) map overlay. Checklists are lists in a structured format of environmental effects and impact indicators designed to stimulate the analyst to consider broadly about possible consequences of contemplated actions. It could effectively gain the attention and awareness of their audience as well. Checklists could be in the simple, descriptive, or scaling and weighing format. Simple checklists are a list of parameters without guidelines on how they are to be interpreted or measured. Descriptive checklists will include the identification of environmental parameters and the guidelines along with the information on how they will be measured, predicted, and assessed. Scaling or weighing checklists are similar to descriptive checklists but provide additional information on the subjective scaling and weighing of the parameters. The checklist method is simple to understand and use. It is useful in summarizing information to make it accessible to specialists from different fields, or to decision-makers who may have a limited amount of technical knowledge. It is good for the site selection and priority setting, particularly for the scaling checklist. However, there are several disadvantages such as it is too general and incomplete, the identification is qualitative and subjective, it does not distinguish between direct and indirect impacts, as well as it does not illustrate the interaction between actions and impact.

A matrix is a two-dimensional table that facilitates the identification of impacts arising from the interaction between project activities and specific environmental components. It is the expansion of checklists that acknowledges the different components of development. The matrix could be in the form of simple, time-dependent, magnitude, quantified, or weighed. The simple matrix presents the impact on the environmental parameters that warrant attention from the different phases of project activities. The time-dependent and magnitude matrix presents the identification of impacts according to their magnitude, importance, and time frame (e.g., short, medium, or long-term). The descriptive matrix also known as the Leopold matrix was developed based on a list of 100 project actions and 88 environmental components for the US geological survey by Leopold in 1971. It provides a framework for the interaction of different activities of a project with potential environmental impacts caused by them. It is easily understood, can be applied to a wide range of developments, and is reasonably comprehensive for the direct impact. The weighted matrix is a matrix that includes weighting the project components toward the assessed impacts on the environmental component. The matrix method has the advantage of allowing various alternatives to be compared numerically. It links the actions to impact and is very good at displaying the impact assessment results. However, it still fails to distinguish between direct and indirect impacts and may potentially result in double-counting the identified impacts.

The network method is an alternative for illustrating the secondary and subsequent effects of the action on environmental elements to construct a network tracing such effects. It uses the matrix approach and extends it to include both the primary as well as secondary impacts in the form of an impact tree. Does the impact tree include direct or indirect impacts? along with the short or long-term impact used to identify cause-effect linkages. The advantage of the network method is that it links action to impact, is useful to check second-order impacts in a simplified form, handles direct and indirect impacts, as well illustrating the mitigation and control measures needed for project activities. One problem encountered in applying the network method is that many higher-order effects can be postulated that are actually unlikely to occur.

The overlay method involves sets of maps that represent the spatial distribution of relevant characteristics relative to the proposed project. This method depends on a set of maps that present certain environmental characteristics. It allows separate mapping of critical environmental features. This method is effective to consider sensitive lands that require protection from human activity, hazardous lands that require protection from natural occurrences, renewable resource areas that need to be protected, or areas specific to cultural heritage. This method is easy to understand and use, has a good display, and is good for setting site selection. However, this method only addresses the direct impacts, not the impact duration or probability.