Environmental Impact Assessment methods.pdf

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
04-05
th
November, 2019
METHODS OF EIA

2. Methods of EIA
Approachesdevelopedtoidentify,predictandvalue
changesofanaction.TheseMethodologiestoquantifyorto
qualifythosechanges.
Adhoc method
Checklist method
Matrix method
Network method
Overlay method
Environmental index using factor analysis
Cost/Benefit analysis
Predictive or Simulation methods
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3. Adhoc method
•Indicatebroadareasofpossibleimpactsbylistingcomposite
environmentalparameters(Ex:floraandfauna)likelytobeaffected
bytheproposedactivity.
•Thesemethodsinvolveassemblingateamofspecialistswho
identifyimpactsintheirareaofexpertise.
•Here,eachparameterisconsideredseparatelyandthenatureof
impacts(longtermorshortterm,reversibleorirreversible)are
considered.
•Thismethodservesasapreliminaryassessmentandhelpsin
identificationofimportantareaslike:Wildlife,Endangeredspecies,
Exoticvegetation,Grazing,Socialcharacteristics,Naturaldrainage,
Groundwater,Noise,Airquality,Visualdescriptionandservices,
Openspace,Recreation,Healthandsafety,Economicvaluesand
Publicfacilities

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:
Itgivesnoassurancethatacomprehensivesetofall
relevantimpactshavebeenstudied
lacksconsistencyasitdifferentcriteriaareselectively
evaluatedbydifferentgroups
Itisinefficienttoidentifyandassembleapanelforeach
assessment.
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6. Checklist method
•Three types:
•1.Simple:noinformationneededonmagnitudeor
importanceofimpacts
•2.Descriptive,requireinformationonmagnitudeor
importanceofimpactsaswellasindicationon
predictionmethodsandindicators.
•3.Questionnaires,threetypesofanswer:“yes”,“no”,“may
be”
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The advantages of this method are:
oIt is simple to understand and use
oIt is good for site selection and priority
setting
Disadvantages of this method are:
oIt does not distinguish between direct and indirect
impacts
oIt does not link action and impact
oIt is cumbersome at times

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13. Basic Rules
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14. 4. Network method:
Thismethodusesthematrixapproachandextendsitto
includeboththeprimaryaswellasthesecondaryimpacts.
Itisshownintheformofatreecalledimpacttree.This
diagramisalsocalledasreferenceorsequencediagram.
Identificationofdirect,indirectalongwithshort,longterm
impactisacrucialandbasicstepofmakinganimpacttree
Theimpacttreeisusedtoidentifycause-effectlinkages
Theimpacttreeisavisualdescriptionoflinkages
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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.
Itenablesseparatemappingofcriticalenvironmental
featuresatthesamescaleasproject'ssiteplan(Ex:
wetlands,steepslopes,soils,floodplains,bedrock
outcrops,wildlifehabitats,vegetativecommunities,
culturalresources,etc)
Intheoldtechnique,environmentalfeatureswere
mapppedontransparentplasticindifferentcolours
Moderntechniqueofthesameactivityisdoneusing
computersoftware,hardware,dataandskilledpeople.
ItiscalledGIS(GeographicInformationSystems)
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•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

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DIRECT AND INDIRECT IMPACTS

20. Primary and Secondary Impacts
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23. There is no single ideal method
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24. Impact Significance
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25. Strategic Environmental Assessment (SEA)
•Itisdefinedastheformalised,systematicand
comprehensiveprocessofevaluatingthe
environmentalimpactsofapolicy,planor
programme(PPP)anditsalternatives,includingthe
preparationofawrittenreportonthefindingsof
thatevaluation,andusingthefindingsinpublicly
accountabledecision-making(Therivel,etal.,1992).
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