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Methods Used to Assess Environmental

ImpactsTraining Workshop on Environmental Assessment-Tool to Achieve Sustainability

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Definition

Impact

Deviations from a baseline situation

Assessment

The exercise of identifying impacts likely to arise from an activity or project, quantifying them, and assessing their significance

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“Steps” in Impact Assessment Conduct baseline study Identify and evaluate alternatives Identify potential impacts Predict impacts Determine impact significance Consider mitigation options Determine residual impacts and environmental

risks Prepare environmental management plan

Scope of the Presentation

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Impact Identification Methods

Briefing, consultation and workshops

Index approaches (matrices and checklists)

Overlays

Networks

Other

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Briefing, Consultation, Workshops

Briefing/brainstorming approaches to scoping frequently used - relies on experience and knowledge of the assessment team.

Consultation with interested groups and statutory bodies

Public participation

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Checklists

A variety of methods varying in complexity and characteristics.

All share the common basis of an index of environmental factors or development activities: Simple checklists Descriptive checklists Questionnaire checklists Weighting-scaling checklists

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Simple Checklists

Provide assessor with a list of factors to be considered.

Used as a memory aid to identify impacts.

Can provide structure to initial part of scoping stage.

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Disease vectors

(a) Are there known disease problems in the project area transmitted throughvector species such as mosquitoes,flies, snails etc. ? yes no not known

(b) Are these vector species associated with: – aquatic habitats ? yes no not known – forest habitats ? yes no not known – agricultural habitats ? yes no not known

(f) Will the project provide opportunitiesfor vector control through improvedstandards of living ? yes no not known

Estimated impact on disease vectors ?

high adverse insignificant high benefit

Example of Checklist

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Advantages and Disadvantages of Checklists

Advantages Comparatively simple method Not necessarily project specific Once established, can be used in many different

situations

Disadvantages Can never be considered as definite or complete Do not help to identify secondary/higher order

impacts Tend to ‘compartmentalise

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Interaction Matrices

Consist of two checklists - development actions on one axis, environmental parameters on the other.

Sometime magnitude or importance of impacts is included in numerical terms.

Presents a clear summary.

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Example of Matrix

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Advantages and Disadvantages of Matrices

Advantages Easily modified, so many varieties have been developed

and used Relationships between development and environment

made explicit Can present a summary of anticipated impacts in an

easily understood format

Disadvantages Fail to identify potential secondary or tertiary impacts May not provide an objective method for comparing

impact magnitudes or importance

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Overlays

Excellent for identifying indirect impacts.

Manual or computer (GIS) based.

Layers of information overlain to form a composite

Overlays can show: spatial extent/intensity of impact over geographical area different land uses or designations different location constraints of proposals identification of alternative sites or routes

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Overlays

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Advantage and Disadvantage of Overlays

Advantages Conceptually simple; Provide clear presentation Highly versatile Appropriate for describing and assessing impacts

occurring over a wide spatial area Can predict geographical location of impacts

Disadvantages Number of layers limited (6 - 8) Needs weighting of parameters Setting boundaries may induce inaccuracies

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Selecting the Right Tool

Considerations in Impact Identification Direct and Indirect Impact Impact of Secondary Development Long-term Impacts Cumulative Impacts

Tool is selected on the bases of: Available resources Nature of project

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Prediction of Impact

Quantitative analysis (simulation models, statistical analysis, etc).

Qualitative analysis (professional judgment, intuitive reasoning, etc)

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Examples of Prediction Methods

Models Air dispersion models Stream water quality model Groundwater models

Standard Data Noise emission data

Technical Literature Research articles on wildlife behavior

Risk Assessment

Community participation

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Significance Criteria

Law, regulation, policy

Acceptable industry standard

Public health and safety risk (high or unknown)

Public concern or acceptable social or cultural values

Precedent-setting and unique characteristics (protected areas, wilderness, aesthetics)

Expert opinion and value judgment

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Output of Impact Assessment

All potential impacts identified.

Impacts predicted, qualitatively or quantitatively.

Impacts characterized: Magnitude Extent Risk (Probability and severity) Duration Reversibility

Significance determined (acceptable or not).