ENVIRONMENTAL IMPACT ASSESSMENT TOOLS

Presentation By Anusha Vytla(10EN05F)

CONTENT

Introduction The Leopold Matrix Description  Identification  Prediction Interpretation Communication Inspection Procedures Advantages and Disadvantages

Environmental Impact Assessment The International Association for Impact Assessment (IAIA)

defines an environmental impact assessment as "the process of identifying, predicting, evaluating and mitigating the biophysical, social, and other relevant effects of development proposals prior to major decisions being taken and commitments made.“

The purpose of the assessment is to ensure that decision makers consider the ensuing environmental impacts when deciding whether to proceed with a project.

Methods for Environmental Impact Assessment

Ad hoc methods are useful when time constraints and lack of information require that the EIA must rely exclusively on expert opinion.

Checklists and matrices are good tools for organizing and presenting information.

Networks are a formalized way of representing the causal chain: activity - changes - impacts - mitigation.

Matrices

Matrix methods identify interactions between various project actions and environmental parameters and components.

They incorporate a list of project activities with a checklist of environmental components that might be affected by these activities. A matrix of potential interactions is produced by combining these two lists (placing one on the vertical axis and the other on the horizontal axis).

One of the earliest matrix methods was developed by Leopold et al. (1971).

In a Leopold matrix and its variants, the columns of the matrix correspond to project actions (for example, flow alteration) while the rows represent environmental conditions (for example, water temperature).

The impact associated with the action columns and the environmental condition row is described in terms of its magnitude and significance.

Types Of Matrices

Matrices require information about both the environmental components and project activities. The cells of the matrix are filled in using subjective (expert)judgement, or by using extensive data bases.

There are two general types of matrices:

1) simple interaction matrices; and

2) significance or importance-rated matrices.

Simple matrix methods simply identify the potential for interaction.

Significance or importance-rated methods require either more extensive data bases or more experience to prepare.

Values assigned to each cell in the matrix are based on scores or assigned ratings, not on measurement and experimentation.

For example, the significance or importance of impact may be categorized (no impact, insignificant impact, significant impact, or uncertain). Alternatively, it may be assigned a numerical score (for example, 0 is no impact, 10 is maximum impact).

Leopold Matrix- Description 

The pioneering approach to impact assessment, the Leopold matrix, was developed by Dr. Luna Leopold and others of the United States Geological Survey (Leopold et. al., 1971). The matrix was designed for the assessment of impacts associated with almost any type of construction project.

The Leopold system is an open-cell matrix containing 100 project actions along the horizontal axis and 88 environmental 'characteristics' and 'conditions' along the vertical axis.

Leopold Matrix- Identification

The Leopold matrix is comprehensive in covering both the physical-biological and the socio-economic environments. The list of 88 environmental characteristics is weak, however, from the point of view of structural parallelism and balance. For example, swimming (an activity) and water temperature (an indicator of state) are both included. In addition, the list is biased towards the physical-biological environment (67 entries). 

The Leopold matrix is not selective, and includes no mechanism for focusing attention on the most critical human concerns. Related to this is the fact that the matrix does not distinguish between immediate and long-term impacts, although separate matrices could be prepared for each time period of interest. 

Leopold Matrix- Prediction 

The method can accommodate both quantitative and qualitative data.

The Leopold matrix contains no provision for indicating uncertainty resulting from inadequate data or knowledge. All predictions are treated as if certain to occur.

Leopold Matrix- Interpretation & Communication 

The Leopold matrix employs weights to indicate relative importance of effects and impacts. A weakness of the system is that it does not provide explicit criteria for assigning numerical values to these weights. 

By providing a visual display on a single diagram, the Leopold matrix may often be effective in communicating results. However, the matrix does not indicate the main issues or the groups of people most likely to be affected by the impact.

Leopold Matrix- Inspection Procedures  The matrix has no capability for making

recommendations on inspection procedures to be followed after completion of the action.

Evaluation of Matrix Methods.Key Area of theAssessment Process

Criteria L denotes Criteria Completely SatisfiedP denotes Criteria Partially SatisfiedN denotes Criteria Not Satisfied

1) Cost / TimeEffectiveness Criteria

1. ExpertiseRequirements

2. Data Requirements

3. Time Requirements

4. Flexibility

5. Personnel Level ofEffort

P

L

P

P

P

2) Impact Identification

6. Comprehensiveness

7. Indicator-based

8. Discriminative

9. Time Dimension

10. Spatial Dimension

L

N

N

N

N

3) Impact Measurement

11. Commensurate

12. Quantitative

13. Measures Changes

14. Objective

N

N

N

P

4) Impact Assessment

15. Credibility

16. Replicability

17. Significance-based

18. Aggregation

19. Uncertainty

20. Alternative Comparison

P

N

N

P

N

N

5) Communication 21. Communicability

22. Summary Format

L

L

Advantages

Most matrices were built for specific applications, although the Leopold Matrix itself is quite general.

They should preferably cover both the construction and the operation phases of the project.

Simple matrices are useful:

1) early in EIA processes for scoping the assessment;

2) for identifying areas that require further research; and

3) for identifying interactions between project activities and specific environmental components.

Disadvantages

However, matrices also have their disadvantages: they tend to overly simplify impact pathways, they do not explicitly represent spatial or temporal

considerations, and they do not adequately address synergistic impacts.

REFRENCES

envfor.nic.in/report/0304/chap-04.pdf www.icsu-scope.org/downloadpubs/

scope5/chapter04.html www.adb.org/Documents/Books/

Environment_Impact/chap3.pdf