Impact Analysis 2. Impact Prediction

Environmental Impacts The change in an environmental parameter, which results from a particular activity or intervention. The change is the difference between the environmental parameter with the project compared to that without the project. It is predicted or measured over a specified period and within a defined area.

Nature Direct impacts – The most obvious impacts are those that are directly related to the proposal can be connected (in space and time) to the action that caused them; – Examples: loss of wetlands ; destruction of habitat. Indirect or secondary impacts: – Changes that are usually less obvious, occurring later in time or further away from the impact source; – Examples: increased cost of medications due to contaminated water

Magnitude It is expressed in terms of relative severity, such as major, moderate or low. Severity, as opposed to size, magnitude, notably whether or not an impact is reversible and the likely rate of recovery. Example: Infiltration of large quantities of highly polluted water into the aquifer

Timing All of the stages of the life cycle of the project should be considered. Some impacts will occur immediately, Others may be delayed, sometimes by many, years. Example: heavy metals will take more than 10 years to reach the groundwater

Duration Some impacts may be short-term, Others may be long-term Certain impacts such as blasting may be intermittent, such as electromagnetic fields caused by power lines, may be continuous.

Summarizing the prediction process

Prediction Techniques There are four basic predictive techniques typically used in impact assessment – Professional judgments; – Quantitative mathematical models; – Experiments and physical models; and – Case studies as analogues or points of reference.

Impact Analysis 3. Impact Evaluation

Impact Evaluation Evaluation is the formal stage at which a test of significance is made. The purpose of impact evaluation is to : – Assign relative significance to the predicted impacts associated with the project. – Determine the order in which impact are to be avoided, mitigated or compensated.

Method Significance is determined by joint consideration of: – Characteristic (as assigned in prediction) – Importance (relative value)

Impact Importance Relevant criteria for impact importance include the following: – Ecological importance – Social importance – Environmental standards – Statistical significance

Ecological importance Effects on plant and animal habitat The presence of rare and endangered species Ecosystem resilience, sensitivity, biodiversity

Social Importance Real or perceived risk to human health and safety Potential loss of commercial production, for example, farmland Recreational or aesthetic value (sports fisheries) Impacts on public resources such as social services Demographic effects

Environmental standards Environmental standards are among the most common means for assessing significance, Examples – Effluent discharge standard, – Clean air standards, – Water quality standards, etc.