1) Methods of EIA 2) Impact Significance 3) Strategic Environmental Assessment (SEA) 4) Primary and Secondary Impacts 5) Advantages and disadvantages of the network method 6) Matrices method 7) Checklist method 8)Types of Ad hoc method 9) Environmental index using factor analysis 10) Cost/Benefit analysis 11) Predictive or Simulation methods

1. Dr. Revanuru Subramanyam
Department of Civil Engineering
NATIONAL WORKSHOP
ON
ENVIRONMENTAL IMPACT ASSESSMENT OF MINING INDUSTRIES
04-05th November, 2019
METHODS OF EIA

2. Methods of EIA
Approaches developed to identify, predict and value
changes of an action. These Methodologies to quantify or to
qualify those changes.
 Adhoc method
 Checklist method
 Matrix method
 Network method
 Overlay method
 Environmental index using factor analysis
 Cost/Benefit analysis
 Predictive or Simulation methods 2

3. Adhoc method
• 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.
• This method serves as a preliminary assessment and helps in
identification of important areas like: Wildlife, Endangered species,
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

4. Types of Ad hoc method
 Opinion poll
 Expert opinion and
 Delphi methods

This method is very simple and can be performed without
any training.
 It provides minimal guidance for impact analysis
The drawbacks of this method are listed below:
 It gives no assurance that a comprehensive set of all
relevant impacts have been studied
 lacks consistency as it different criteria are selectively
evaluated by different groups
 It is inefficient to identify and assemble a panel for each
assessment.
4

5. 5

6. Checklist method
• Three types:
• 1. Simple : no information needed on magnitude or
importance of impacts
• 2. Descriptive, require information on magnitude or
importance of impacts as well as indication on
prediction methods and indicators.
• 3. Questionnaires, three types of answer: “yes”, “no”, “may
be”
6

7. 7

8. 8

9. 9
The advantages of this method are:
o It is simple to understand and use
o It is good for site selection and priority
setting
Disadvantages of this method are:
o It does not distinguish between direct and indirect
impacts
o It does not link action and impact
o It is cumbersome at times

10. 10

11. 11

12. 12

13. Basic Rules
13

14. 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
14

15. 15

16. 16
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

17. Overlay 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)
17

18. 18
• 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

19. 19
DIRECT AND INDIRECT IMPACTS

20. Primary and Secondary Impacts
20

21. 21

22. 22

23. There is no single ideal method
23

24. Impact Significance
24

25. Strategic Environmental Assessment (SEA)
• It is defined as the formalised, systematic and
comprehensive process of evaluating the
environmental impacts of a policy, plan or
programme (PPP) and its alternatives, including the
preparation of a written report on the findings of
that evaluation, and using the findings in publicly
accountable decision-making (Therivel, et al., 1992).
25

26. 26