EIA Methodologies

Lecture ENV.7
Date: 4/11/24
 Introduction
• Many times, an EIA analyst involved in the preparation of an EIA report, is
faced with a vast quantity of raw and usually unorganized data. Hence, each
technique and method for the evaluation of impacts should have the following
qualities and characteristics:
1. It should be systematic in approach;
2. It should be able to organize a large mass of heterogeneous data;
3. It should be able to quantify the impacts;
4. It should be capable of summarizing the data;
5. It should be able to aggregate the data into sets with the least loss of
information because of the aggregations;
6. It should have a good predictive capability;
7. It should extract the salient features,
and 8. It should finally be able to display the raw data and the derived
information in a meaningful fashion.
CRITERIA FOR THE SELECTION OF EIA
METHODOLOGY
• Each of the different methodologies for the assessment of environmental
impacts of development projects have their advantages and
disadvantages and their utility for a particular application is largely a
matter of choice and judgment of the analyst. Nevertheless, some
objective criteria exist in making such a choice and these are stated
below under the key areas that involve the assessment process.
Generally
• (a) Simplicity: The methodology should be simple so that the available
manpower with limited background knowledge can grasp and adopt it
without much difficulty.
• (b) Manpower, time and budget constraints: The methodology should
be applied by a small group with a limited budget and under time
constraints.
• Flexibility: The methodology should be flexible enough to allow for
necessary modifications and changes through the course of the study.
• Impact Identification:
• (a) Comprehensiveness : The methodology should be sufficiently
comprehensive to contain all possible options and alternatives and should
give enough information on them to facilitate proper decision-making.
• (b) Specificity: The methodology should identify specific parameters on
which there would be significant impacts.
• (c) Isolation of project impacts: The methodology should suggest
procedures for identifying project impacts as distinguished from future
environmental changes produced by other causes.
• (d) Timing and duration : The methodology should be able to identify
accurately the location and extent of the impacts on a temporal scale.
• Impact Measurement
• (a) Commensurate units: The methodology should have a
commensurate set of units so that comparison can be made between
alternatives and criteria.
• (b) Explicit indicators : The methodology should suggest specific and
measurable indicators to be used to qualify impacts on the relevant
environmental parameters.
• (c) Magnitude: The methodology should provide for the
measurement of impact magnitude, defined as the degree of
extensiveness of scale of the impact, as distinct from impact
importance, defined as the weighting of the degree of significance of
the impact.
• (d) Objective criteria: It should be based on objective criteria and the
criteria should be stated explicitly
• Impact Interpretation and Evaluation
• (a) Significance : The methodology should be able to assess the
significance of measured impacts on a local, regional and national scale.
• (b) Explicit criteria : The criteria and assumptions employed to determine
impact significance should be explicitly stated.
• (c) Portrayal of "with" and "without" situation : The methodology should
be able to aggregate the vast amounts of information and raw input data.
• (d) Uncertainly : Uncertainty of possible impacts is a very real problem in
environmental impact assessment. The methodology should be able to
take this aspect into account.(not used )
• (e) Risk: The methodology should identify impacts that have low
probability of occurrence but a high potential for damage and loss.
(minimize or avoid)
• Depth of analysis : The conclusions derived from the methodology
should be able to provide sufficient depth of analysis and instill
confidence in the users, including the general public.
• (g) Alternative comparison : It should provide a sufficiently detailed
and complete comparison of the various alternatives readily available
for the project under study.
• (h) Public involvement: The methodology should suggest a
mechanism for public involvement in the interpretation of the
impacts and their significance.
• Impact Communication
• (a) Affected parties : The methodology should provide a mechanism for
linking impacts to specific effected geographical or social groups.
• (b) Setting description: It should provide a description of the project setting to
aid the users in developing an adequately comprehensive overall perspective.
• (c) Summary format: It should provide the results of the impact analysis
summarized in a format that will give the users, who range from the lay public
to the decision makers, sufficient details to understand it and have confidence
in its assessment.
• (d) Key issues : It should provide a format for highlighting the key issues and
impacts identified in the analysis.
• (e) Compliance: One of the most important factors in choosing a methodology
is whether it can comply with the terms of reference established by the
controlling agency.
 EIA METHODS
• EIA METHODS There is a range of methods from the simplest to complex approaches that
developers, consultants and academics who aim to further “best practice” may wish to
investigate further.
List of Environment EIA Methods
• The following are the important methodologies of utility for assessing the impacts of
developmental activities on the environment.
• I. Adhoc methods
• 2. Checklists methods
• 3. Delphi
• 4. Matrices methods
• 5. Networks methods or impact trees
• 6. Overlays methods
• 7. Environmental index using factor analysis
• 8. Cost/benefit analysis
• 9. Predictive or Simulation methods
• Ad hoc Methods
• Basically ad hoc methods indicate broad areas of possible impacts by
listing composite environmental parameters (for example flora and
fauna) likely to be affected by any development. Ad hoc methods
involve assembling a team of specialists to identify impacts in their
area of expertise.
• In this method, each environmental area, such as, air, and water, is
taken separately and the nature of the impacts, such as, short-term
or long term, reversible or irreversible are considered.
• Ad hoc methods are for rough assessment of total impact giving the
broad areas of possible impacts and the general nature of these
possible impacts. For example, the impacts on animal and plant life
may be stated as significant but beneficial.
• In the ad hoc methods, the assessor relies on intuitive approach and makes a broad-based
qualitative assessment. This method serves as a preliminary assessment which helps in identifying
more important areas like :
• Wildlife
• Recreation
• Endangered species
• Health and safety
• Natural vegetation
• Economic values
• Exotic vegetation
• Visual description and services
• Grazing
• Open space
• Social characteristics
• Public facilities
• Natural drainage
• Groundwater
• Noise
• Air Quality
• The ad hoc methods, while being very simple can be performed
without any training, merely present the pertinent information of a
project's effects on the environment without any sort of relative
weighting or any cause-effect relationship. It provides minimal
guidance for impact analysis while suggesting broad areas of possible
impacts. It does not even state the actual impacts on specific
parameters that will be affected. Ad hoc method is a simple
approach to identify the total impacts of a project and would
consider each environmental area. The ad hoc method involves
assembling a team of specialist to identify impacts in their area
expertise i.e., expert opinion. The advantage of expert opinion data
gathering techniques is its speed and inexpensiveness.
• The ad hoc method has the following drawbacks:
(a) It gives no assurance that it encompasses a comprehensive set of all
relevant impacts;
(b) It lacks consistency in analysis as it may select different criteria to
evaluate different groups of factors;
(c) It is inherently inefficient- as it requires a considerable effort to identify
and assemble an appropriate panel for each assessment and
(d) It is inherent subjectivity and biasness.
Checklist Methodologies
• Checklists are an advance on ad hoc methods in that they list biophysical,
social and economic components, which are likely to be affected by a
development, in more detail.
• Checklist methodologies range from listings of environmental factors in
highly structured approaches involving importance weightings for factors
and application of scaling techniques for the impacts of each alternative
on each factor.
• Checklists in general are strong in impact identification and are capable of
bringing them to the attention and awareness of their audiences. 
Impact identification is the most fundamental function of an EIA and in
this respect, all types of checklists, namely simple, descriptive, scaling
and weighting checklists do equally well.
• Checklists are of four broad categories and represent one of the basic
methodologies used in EIA. They are:
• (a) Simple Checklists: that are a list of parameters without guidelines
provided on how to interpret and measure an environmental parameter.
• (b) Descriptive Checklists: that includes an identification of environmental
parameters and guidelines on how parameter data are to be measured.
• (c) Scaling Checklists: that are similar to descriptive checklist with the
addition of information basis to subjective scaling or parameter values.
• (d) Scaling Weighting Check Lists: are capable of quantifying impacts. a
static or in-motion scale primarily used to ensure that the
items being weighed are within a specific acceptable weight
range.
• Advantage
Check lists are mainly useful for
a) It promotes thinking about the array of impacts in a systematic way
and allows concise summarization of effects.
b) It is the simplest assessment methodologies
c) Summarizing information to make it accessible to experts in different
fields or decision makers who have little technical knowledge.
d) Preliminary analysis will be available in scaling check lists.
e) Information on eco system functions can be clearly understood from
weighing methods.
• Some of the draw backs/Limitations of check lists are
• 1) Checklists do not usually include direct cause-effect links to project
activities.
• 2) Checklist may be too general or incomplete
• 3) They do not illustrate interactions between effects
• 4) The same effect may be registered in several places under heading that
overlap in content (double counting).
• 5) The number of categories to be reviewed can be immense thus
destructing attention from the more significant impacts.
• 6) Involves the identification of effects which are qualitative and subjective.
• 3- Delphi
Delphi is a method of collecting opinions, from different expertise. Large number of
opinion givers than panels or brainstorming sessions. Also enables collecting opinions
and using the information in developing dynamic models Special characteristic.
• Procedure
• 1) A structured, formal and detailed questionnaire is given to the participants by
mail or in person.
• 2) The organizer of the Delphi then collects, analyses, combines and averages the
responses and represents them medians.
• 3) Questionnaire for second round are given with modification if necessary.
• 4) The averaged response of 1st questionnaire is provided to the participants
(where the participants may be asked to respond to scaled objective item.)
• 5) After scrutinizing 2nd round, respondents may be asked to justify the response
• 6) Further interactions are continued, if necessary
• 7) Convergence of opinion emerges (NOT BY FORCE)
• Limitations
• The role of the Delphi coordinator is crucial and subjective biases may be
introduced through this route.
• Lack of item clarity or the common interpretation of scales and feedback
may lead to invalid results.
• Delphi is time consuming and if the questionnaires are long, one may tend
to fill them in a casual manner.
• 4.Matrix Methods
•Matrices are grid like tables used to identify the interaction between project
activities and environmental characteristics.
• While checklists are “one dimensional” lists of potential impacts which tell
whether an impact will occur or not, matrices are ‘two dimensional’ lists which
also give an indication of the ‘magnitude’ of likely impacts. Matrices are thus
checklists of a higher dimension and contain more information than the latter.
•Matrices are the most commonly used method of impact identification in EIA.
• Simple matrices are merely two-dimensional charts showing environmental
components on project (e.g. construction, operation, decommissioning,
buildings, access road etc.) have different impacts.
• Three-dimensional matrices have also been developed in which the third
dimension refers to economic and social institutions: such an approach identifies
the institutions from which data are needed for the EIA process, and highlights
areas in which knowledge is lacking.
• In matrix methods interactions between various activities and
environmental parameters will be identified and evaluated. Matrix
methods are basically generalized checklists where one dimension of a
matrix is a list of environmental social and economic factors likely to be
affected by a project activity. The other dimension is a list of actions
associated with development
• Matrices provide cause-effect relationships between the various project
activities and their impacts on the numerous environmentally important
sectors or components. Matrices provide a graphic tool for display
impacts to their audience in a manner that can be easily comprehended.
• Simple matrices, though able to identify first order effects, cannot show
higher interactive effects between impacts. Simple, interaction matrices
largely overcome this limitation. But such matrices are generally useful
for depicting ecological interactions only for the sake of documentation.
• SALIENT FEATURES OF MATRICES METHODS
• It is necessary to define the spatial boundaries of environmental factors.
Spatial boundaries, defined as geographic differences where
people are located, are fundamental to the study of
distributed work. The temporal phases and specific actions associated
with the proposed project: and the impact rating or summarization scales
used in the matrix.
• 2. A matrix should be considered a tool for purposes of analysis, with the key
need being to clearly state the rationale utilized for the impact ratings
assigned to a given temporal phase and project action, and a given spatial
boundary and environmental factor.
• 3. The development of one or more preliminary matrices can be a useful
technique in discussing a proposed action and its potential environmental
impacts. This can be helpful in the early stages of a study to assist each team
member in understanding the implications of the project and developing
detailed plans for more extensive studies on particular factors and impacts.
• The interpretation of impact ratings should be carefully and critically
considered, particularly when realizing that there may be large
differences in spatial boundaries as well as temporal phases for a
proposed project.
• 5. Interaction matrices can be useful for delineating the impacts of
the first and second or multiple phases of a two-phase or multi phase
project; the cumulative impacts of a project when considered relative
to the other past, present; and reasonably foreseeable future actions
in the area; and the potential positive effects of mitigation measures.
• If interaction matrices are used to display comparisons between different
alternatives, it is necessary to use the same basic matrix in terms of spatial
boundaries and environmental factors, and temporal phases and project
actions for each alternative being analyzed. Completion of such matrices can
provide a basis for trade off analysis.
• 7. Impact qualification and comparisons to relevant standards can provide a
valuable basis for the assignment of impact ratings to different project
actions and environmental factors.
• 8. Color codes can be used to display and communicate information on
anticipated impacts. For example, beneficial impacts could be shown by
using green or shades of green; whereas, adverse effects could be depicted
with red or shades of red.
• One of the concerns relative to interaction matrices is that project
actions and/ or environmental factors are artificially separated, when
they should be considered together. It is possible to use footnotes in
matrix to identify groups of actions, factors, and/or impacts which
should be considered together. This would allow the delineation of
primary and secondary effects of projects.
• 10. The development of a preliminary interaction matrix does not
mean that it would have to be included in a subsequent EA or EIS. The
preliminary matrix could be used as an internal working tool in study,
planning and development.
• 11. It is possible to utilize importance weighting for environmental
factors and project actions in a simple interaction matrix. If this
approach is chosen, it is necessary to carefully delineate the rationale
upon which differential importance weights have been assigned.
Composite indices could be developed for various alternatives by
summing up the products of the importance weights and the impact
ratings.
• 12. Usage of an interaction matrix forces the consideration of actions
and impacts related to a proposed project within the context of other
related actions and impacts. In other words, the matrix will prevent
overriding attention being given to one particular action of
environmental factors.
• NETWORK METHODS
• Networks can identify direct and indirect impacts, higher order effects and
interactions between impacts, and hence are able to identify and
incorporate mitigation and management measures into the planning stages
of a project. They are suitable for expressing ecological impacts but of lesser
utility in considering social, human and aesthetic aspects.
• This is because weightings and ratings of impacts are not features of
network analysis.
• Development of network diagrams
• Fig. 2.3 present the potential impact pathways as casual chains will be very
usefull for displaying first ,secondary, tertiary and higher order impacts.
• The limitation of the network approach :-
• minimal information provided on the technical aspects of impact prediction
and the means for comparatively evaluating the impacts of alternatives.
• networks can become very visually complicated.
•Networks generally consider only adverse impacts on the environment and
hence decision - making' in terms of the cost and benefit of a development
project to a region is not feasible by network analysis.
• Temporal considerations are not properly accounted for, and short term
and long-term impacts are not differentiated to the extent required for an
easy understanding.
•the display becomes very large and hence unwieldy when large regional
plans are being considered.
•provide no avenue for public participation.
• Map overlay/GIS techniques Overlay maps have been used in
environmental planning since the 1960s, before the NEPA was enacted. A
series of transparencies is used to identify, predict, assign relative
significance to and communicate impacts. In this technique a base map is
prepared, showing the general area within which, the project may be
located. Successive transparent overlay maps are then prepared for the
environmental components that, in the opinion of experts, are likely to be
affected by the project.
•Overlay methods involve preparation of a set of transparent maps,
which represent the spatial distribution of an environmental
characteristic (e.g., Extent of dense forest area).
•Information on wide range of variables will be collected for standard
geographical units within the study area which will be recorded on
series of maps typically one for each variable.
•These maps wiIl be overlaid to produce a composite
• Fig 2.8.
•The resulting composite maps characterize the area's physical, social
ecological, land use and other relevant characteristics relative to the
location of the proposed development.
Overlays are very subjective in that they rely on the judgment of the analyst
to evaluate and assess questions on compatibility relating to the existing
land use patterns and the prospects of the development activity.
• In practice, overlays are self-limiting because there is a practical limit on
the number of transparencies that can be overlaid.
•Overlays are useful when addressing questions of site and route selection.
•They provide a suitable and effective mode of presentation and display to
their audiences.
• But overlay analysis cannot be the sole criterion for environmental impact
assessment.
• The considerations in overlay analysis are purely spatial,
•temporal considerations being outside its scope.
• Social, human and economic aspects are not accorded any consideration.
•Further, higher order impacts cannot be identified.
• The methodologies rely on a set of maps of environmental characteristics
(physical, social, ecological, aesthetic) for a project area. These maps are
overlaid to produce a composite characterization of the regional environment.
• The approach seems most useful as a method of screening alternative
project sites or routes, before detailed impact analysis. The overlay approach
is generally effective for selecting alternatives and identifying certain types of
impacts;
• however, it cannot be used to quantify impacts to identify secondary and
tertiary interrelationships.
• A significant application of GIS is the construction of real world models
based on digital data.
•Modeling can analyze trends identify factors that are causing them reveal
alternate paths to solve the given problem and indicate the implications or
consequences of decisions. GIS can show how a natural resource will be
affected by a decision.
•GIS is a powerful management tool for resource managers and planners. Its
applications are limited only by the quality, quantity and coverage of data
that are fed into the system.
•Some of the standard GIS applications are integrating maps made at
different scales.
•Overlaying different types of maps, which show different attributes and
identifying, required areas within a given distance from roads or rivers.
• The overlay maps method is particularly useful for identifying optimum
corridors for developments such as electricity lines, roads, and grazing land,
for comparisons between alternatives, and for assessing large regional
developments. Limitations
•It does not consider factors such as the likelihood of an impact, secondary
impacts or the difference between reversible and irreversible impacts.
•It requires the clear classification of often indeterminate boundaries (such as
between forest and field), and so is not a true representation of conditions on
the ground.
•It relies on the user to identify likely impacts before it can be used.
COST/BENEFIT ANALYSIS
•Cost/benefit analysis provides the nature of expense and benefit accruable
from a project in monetary terms as a common practice in traditional feasibility
studies and thus enables easy understanding and aids decision-making.
•The principal methods available for placing monetary values (costs and
benefits) on environmental impacts, a taxonomy of valuation methods, and steps
involved in economic evaluation of environmental impacts are discussed under
this category.
•The role of environmental economics in an EIA can be divided into three
categories, namely:
I. The use of economics for "benefit-cost analysis" as an integral part of project
selection;
2. The use of economics in the assessment of activities suggested by the EIA and
3. The economic assessment of the environmental impacts of the
• Environmental economics can aid in the selection of projects in that benefit-
cost analysis can be used in the prescreening stage of the project, and the
environmental components can be brought into the process of presenting
various options and selecting among them.
• Doing so eventually leads to a project selection process, which takes the
environment into consideration.
• In the second role, the economic assessment is focused on the cost assessment
of environmental mitigation measures and management plans suggested in the
EIA.
• The economic analysis in the EIA may include a summary of the project costs
and how such cost estimates would change due to the activities proposed
under the EIA. This component can be considered as an accounting of the
environmental investment of a project.
• The third role, which is the economic assessment of the environmental
impacts of a project, is geared towards seeking the economic values (of both
costs and benefits) of the environmental impacts. These impacts are neither
mitigated, nor taken into account in traditional economic analysis of
projects. They should be identified by the EIA and sufficient quantitative and
qualitative explanations should be given in EIA documents.

• The difficulty encountered in the use of these techniques will be that

impacts have to be transformed and stated in explicit monetary terms, and
this is not always possible, especially for intangibles like the monetary value of
health-related impacts of industrial development.
• STEPS IN ECONOMIC VALUATION OF ENVIRONMENTAL IMPACTS
•Economic analysis of environmental impacts is important in project
preparation to determine whether the net benefits of undertaking the
project are greater than the alternatives, including the non-project
scenario.
• Project alternatives often vary in their economic contribution and
environmental impacts.
• Economic assessment of different alternatives in the early stages of
project planning should provide important inputs to improve the quality of
decision making.
•The economic analysis of the environmental impacts of the selected
projects also allows for amore complete assessment of the project‘s costs
and benefits.
• At a minimum, the following six tasks need to be completed in the economic
analysis of environmental impacts
1. determine the spatial and conceptual boundaries of the analysis;
2. identify environmental impacts and their relationships to the project;
3. quantify environmental impacts and organize them according to importance
– the impacts described qualitatively, if they cannot be expressed in
quantitative terms;
4. choose a technique for economic valuation;
5. economic valuation (place monetary values) of environmental impacts
identified; and 6. set an appropriate time frame and perform the extended
benefit cost analysis.
• Simulation Modeling
System analysts have developed an approach to environmental impact
assessment and management commonly referred to as Adaptive
Environmental Assessment and Management (AEAM), which combines various
simulation models to predict impacts.
This approach broadens the potential of simulation models to evaluate the
impacts of alternatives and is beneficial for project planning.
• overcomes the short-comings of most other methods in that other methods
assume unchanging conditions or project impacts in a single time frame on
statistically described environmental conditions
•The technique can be time-consuming and may impose a severe burden on
the monetary resources available for the purpose of environmental
assessment.
•Simulation models especially of ecosystems, are still in an embryonic stage
of development and their accuracy and predictive capacity is yet to be
proved.
•The use of this technique requires the input of people trained in its use and
functions.
•This may lead to the need for expatriate expertise in proportions greater
than required for other techniques and this may be the limiting constraint
• Summary EIA METHODS CONT… Impact assessment methodologies range
from simple to complex and are also progressively changing from a static,
piecemeal approach to the one that reflects the dynamism of nature and the
environment. Consequently, the trend is away from mere listing of potential
impacts towards more complex modes whereby the methodology can
identify feedback paths, higher order impacts than merely those apparent,
first order ones, and uncertainties. In short, the methodological trend is
approaching an overall management perspective requiring different kinds of
data different in formats and varying levels of expertise and technological
inputs for correct interpretation. It is important to understand their
drawbacks in order to determine which of the methods are most
appropriate. An evaluation of various methodologies is presented in Table
2.1