Methods of EIA

1. Ad Hoc Method:

• An ad hoc method is a team of experts assembled for a short time to conduct an EIA.
• The information is stated in simple terms that are readily understood by the lay person.
• No information about the cause-effect relationship between project actions and environmental components is provided.

Drawbacks of Ad Hoc Method

• It may not encompass all the relevant impacts
• Because the criteria used to evaluate impacts are not comparable, the relative weights of various
• Impacts cannot be compared;
• It is inherently inefficient as it requires sizable effort to identify and assemble an appropriate panel of experts for each assessment; and
• It provides minimal guidance for impact analysis while suggesting broad areas of possible impacts.

2. Checklists:

• Checklists are standard lists of the types of impacts associated with a particular type of project.
• Checklists methods are primarily for organizing information or ensuring that no potential impact is overlooked.
• Sophisticated checklists include:

1) Scaling checklists in which the listed impacts are ranked in order of magnitude or severity, and

2) Weighting-scaling checklists, in which numerous environmental parameters are weighted (using expert judgment), and an index is then calculated to serve as a measure for comparing project alternatives.

There are four general types of checklists:

1. Simple Checklist: a list of environmental parameters with no guidelines on how they are to be measured and interpreted.
2. Descriptive Checklist: includes an identification of environmental parameters and guidelines on how to measure data on particular parameters.
3. Scaling Checklist: similar to a descriptive checklist, but with additional information on subjective scaling of the parameters.
4. Scaling Weighting Checklist: similar to a scaling checklist, with additional information for the subjective evaluation of each parameter with respect to all the other parameters.

Drawbacks of Checklists

1. They are too general or incomplete;
2. They do not illustrate interactions between effects;
3. The number of categories to be reviewed can be immense, thus distracting from the most significant impacts; an
4. The identification of effects is qualitative and subjective.

3. Matrix method:

• 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).
• Matrices require information about both the environmental components and project activities.

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.