Methods of EIA

Methods of EIA

Listed below are the important methodologies for assessing the impacts of any
developmental activity on the environment:

1. Adhoc method
2. Checklist method
3. Matrix method
4. Network method
5. Overlay method
6. Environmental index using factor analysis
7. Cost/Benefit analysis
8. Predictive or Simulation methods

These methods might vary from:

Simple to Complex
Static piece-meal approach to Dynamic nature of the environment

The change in EIA is moving away from a simple listing of potential impacts to complex
modes involving identification of feedback paths leading to higher order impacts as
compared to the easily visible first order impacts involving uncertainities. This approach can
be considered as an overall management technique requiring different

kinds of data in different formats along with varying levels of expertise and technological
inputs to accurately forecast the results of any planned development.

1. Ad hoc methods

Ad hoc methods indicate broad areas of possible impacts by listing composite environmental
parameters (Ex: flora and fauna) likely to be affected by the proposed activity.
These methods involve assembling a team of specialists who identify impacts in their area of
expertise. Here, each parameter is considered separately and the nature of impacts (long
term or short term, reversible or irreversible) are considered.
These methods give a rough assessment of total impact while giving the broad areas and
the general nature of possible impacts. In this method, the assessor relies on an intuitive
approach and makes a broad-based qualitative assessment. This method serves as a
preliminary assessment and helps in identification of important areas like:

 Wildlife
 Endangered species
 Natural vegetation
 Exotic vegetation
 Grazing
 Social characteristics
 Natural drainage
 Groundwater
 Noise
 Air quality
 Visual description and services
 Open space
 Recreation
 Health and safety
 Economic values and
 Public facilities

Types of Ad hoc method are:

 Opinion poll
 Expert opinion and
 Delphi methods

This method is very simple and can be performed without any training. It does not involve
any relative weighting or any cause-effect relationship.
It provides minimal guidance for impact analysis while suggesting broad areas for possible
impacts. Moreover, it does not even state the actual impacts on specific parameters that will
be affected.
The drawbacks of this method are listed below:

1. It gives no assurance that a comprehensive set of all relevant impacts have been
studied
2. Analysis using this method lacks consistency as it different criteria are selectively
evaluated by different groups
3. It is blatantly inefficient as it requires a considerable effort to identify and assemble a
panel for each assessment.
2. Checklist method
In this method, environmental factors are listed in a structured format by giving importance
weightings for factors and application of scaling techniques for impacts of each alternative.
Checklists are strong indicators of impact identification. They effectively garner the attention
and awareness of their audience. Impact identification is a fundamental function of an EIA.
Checklists may be:
1. Simple
2. Descriptive
3. Scaling or
4. weighting type
Simple checklists are a list of parameters without guidelines regarding either interpretation
or measurement of environmental parameters or specific data needs or impact prediction
and assessment.

Descriptive checklists include list of environmental factors along with information on

measurement, impact prediction and assessment.

Scaling and weighting checklists facilitate decision making. Such checklists are strong in
impact identification. While including the function of impact identification, they include a
certain degree of interpretation and evaluation. The aforementined factors make these
methods attractive to decision-making analysis.
However, the scaling and weighting methods are subjective and hence pose the danger of
imparting equal importance to every impact. Another defect observed by critics is that
numerical values assigned to impacts can be derived on the basis of expert knowledge and
judgement alone.
Scaling and weighting checklist techniques quantify impacts reasonably well although they
use subjective extimates. However, they make no provision for assessing dynamic
probabilistic trends or mitigation, enhancement and monitoring programmes. These
methods cannot identify higher order effects, impacts and interactions.

Simple and descriptive checklists simply identify the possible potential impacts without any
rating regarding their relative magnitudes.

Scaling and weighting checklists remove decision making from the hands of decision makers
while they impart a single number to various inherently different impacts and this aspect
prevents the decision maker to consider the possibility of trade-offs.

In checklist method, the impacts are tabulated in the form of cells with information either in
the descriptive form that gives information regarding possibility or potential existence of an
impact whereas in the scaling or weighing methods the magnitude or importance of impact
is given. Sample checklists or weighing methods used in EIA are shown below:
The advantages of this method are:

1. It is simple to understand and use

2. It is good for site selection and priority setting
Disadvantages of this method are:
1. It does not distinguish between direct and indirect impacts
2. It does not link action and impact
3. It is cumbersome at times

3. Matrix Method
This methodology provides a framework of interaction of different activities of a project with
potential environmental impacts caused by them. A simple interaction matrix is formed
when project actions are listed on one axis (usually vertical) and environmental impacts are
listed along the other axis. This technique was pioneered by Leopold et al in 1971. It lists
about 100 project actions and about 88 environmental charateristics and conditions. An
example of this matrix is shown below:
Similarly, a sectoral matrix is shown below:
 The advantage of the matrix method is that it links action to impact
 This is a very good method for displaying EIA results

The disadvantages of this method are listed below:

 It is difficult to distinguish between direct and indirect impacts using this method
 There is potential for double-counting of impacts
 It is qualitative in nature and does not refer to quantity of impact
4. Network method:

 This method uses the matrix approach and extends it to include both the primary as
well as the secondary impacts
 It is shown in the form of a tree called impact tree. This diagram is also called as
reference or sequence diagram
 Identification of direct, indirect along with short, long term impact is a crucial and
basic step of making an impact tree
 The impact tree is used to identify cause-effect linkages
 The impact tree is a visual description of linkages
 The diagram below shows the example of a network analysis:
The advantages of the network method are:

 It links action to impact

 It is useful to check second order impacts in a simplified form
 It handles direct and indirect impacts
The disadvantages of this method are:
 It becomes overly complex if used beyond simplified version
 It is completely qualitative in nature
5. Overlays
 This method depends on a set of maps of a project area's environmental
characteristics covering physical, social, ecological and aesthetic aspects
 It enables separate mapping of critical environmental features at the same scale as
project's site plan (Ex: wetlands, steep slopes, soils, floodplains, bedrock outcrops, wildlife
habitats, vegetative communities, cultural resources, etc)
 In the old technique, environmental features were mappped on transparent plastic in
different colours
 Modern technique of the same activity is done using computer software, hardware,
data and skilled people. It is called GIS (Geographic Information Systems)
The advantages of this method are:
 It is easy to understand and use
 It has a good display and
 It is good for setting site selection
The disadvantages of this method are:
 It addresses only direct impacts
 It does not address impact duration or probability

13 EIA Methodology
SUNIL MITTAL

1. Introduction
1.1 Desirable of EIA methodologies
1.2 Criteria for selection of EIA Methodology
1.3 Choosing a Method
1.4 Objectives of methodologies
1.5 Focus of Methodology
1.6 Methodology Requirements
2. Major Methodologies of EIA
2.1 Ad Hoc
2.2 Checklists
2.3 Matrices
2.4 Networks
2.5 Overlays

1. Introduction

EIA methodology is a structural approach developed to identify, predict and value

changes of an action. Changes are reflected to the sequence of activities, steps
regarding the environmental issues (physical, chemical, biological, socioeconomic,
cultural, landscape values and processes). The methodology uses in process quantify
these changes. 1.1.

1.1. Desirable of EIA methodologies

EIA Methodology are based on principle of equality, openness, cost-

effectiveness and efficiency approaches. Broadly these are 4 types.

(a) Comprehensive: Recognize intricate systems and bound complex inter-

relationship.
 (b) Selective: Pinpoint critical (significant) impacts and eliminate as early as
possible unimportant impacts.

(c) Comparative: Determine environmental changes due to the project activities

compared with under existing conditions (Before starting project).

(d) Objective: Provide unbiased measurements free from political and external
influences.

1.2. Criteria for selection of EIA Methodology

Simplicity: The methodology should be simple and based on available

manpower & background knowledge. It can be adapted without much difficulty.

Budget and Time: The methodology should be applied by small group with under
approve budget and limited time span.

Flexibility: The method should be flexible and allow the modifications and changes
during course of study.

1.3. Choosing a Method

The methodology of EIA ranges from simple to complex and requires different
kinds of data, several data formats, expertise and technological skill for their
interpretation. Their analyses produce differing levels of precision and certainty. All
of these factors should be considered for selecting a suitable methodology.

1.4. Objectives of methodologies:

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
7. Monitoring and impacts management

1.5. Focus of Methodology

 Potential impacts and their types of environmental components Natural and social
systems Time and space

1.6. Methodology Requirements

The EIA practitioner faces vast varieties of raw and unorganized information that
must be collected and analyzed in preparation of an EIA report. The best methods are
able to:

 Organize a large mass of heterogeneous data Allow summarization of data

 Aggregate the data into smaller sets with least loss of information
 Display the raw data and the derived information in a direct and relevant fashion
 Target audience should also be considered (example if target audience are not
educated then, use of color code, size, cross etc. should be used rather that figures
and tables)

2. Major Methodologies for EIA

Following are the 5 major methodologies of EIA.

a) Ad Hoc
b) Checklists
c) Matrices
d) Networks
e) Overlays

a) Ad Hoc Method: This is a simple method and based upon broad environmental
impacts aspects. This method is very useful whenever time period is limited with lack
of require scientific information. In such situation, EIA depends exclusively on
background, expertise and experience of experts. This method is not recommended,
when more scientific methods are available.

Types of Ad Hoc Method

 Opinion polls
 Expert opinion
 Delphi methods etc.

Advantage:
 Simple and easily understandable.
 The experts of a respective areas guide EIA.
 Overall environmental components are enlisted.

Disadvantage:

 It required expert person.

 The identification and prediction of short & long term impacts are poor because it
examined on guess basis.
 It provides minimal guidance for impact analysis, while suggesting subjective area of
impacts
 Not good for organizing, reviewing and interpreting data

b) Checklists:

Checklists are standard lists of the types of environmental potential impacts,

which may be associated with respective project. The lists are prepared with
highly structured approaches and involve importance with weighing of factors
and ensure that no potential impact is overlooked. Checklists are very effective in
impact identification and capable to spread awareness & attention for respective
people.

Checklists should enable identification of impacts on Soil, Water, Atmosphere,

Flora, Fauna, Resources, Recreation and Cultural etc. status.

A typical checklist might contain entries such as:

 Earth: Mineral Resources, Construction Material, Soils, Land form, Force fields and
Background Radiation, Unique physical features
 Water: Surface water like rivers, lakes and reservoirs, estuaries, coastal seas and
ocean, Groundwater quality, Snow, Ice
 Atmosphere: Quality regarding gases & particles), Climate, Temperature
 Flora: Trees, Shrubs, Grass, Crops, Micro & Macro flora, aquatic plants; endangered
species; barriers; corridors
 Fauna: birds; land animals including reptiles; fish and shellfish; benthic organisms;
insects; micro fauna; endangered species; barriers; corridors
 Land Use: Wilderness and open space, Wetlands, Forestry; Grazing, Agriculture,
Residential, Commercial, Industrial, Mining and Quarrying
 Recreation: Hunting; Fishing; Boating, Swimming, Camping and Hiking,
Picnicking,Resorts

Types of Checklists

(i) Simple Checklist

(ii) Descriptive Checklists
(iii)Scaling Checklist
(iv) Scaling Weighting Checklist
(v) Questionnaire Checklist

(i) Simple Checklist

Simple checklist consist simple list of environmental parameters and no information

needed on the magnitude or importance of impacts.Checklist can recognize
resource/environmental component, which affects by particular activities.

The example given below (Table 1) for construction sites, the tick mark confirm
that impact is there, where no tick mark or leaving the box means no impact.