2. WHAT IS AN IMPACT ????????????
An Impact is the action of one object
coming forcibly in to contact with another.
Once all the important impacts have been
identified, their potential size and
characteristics can be predicted.
3. IMPACT PREDICTION
Impact prediction is the forecasting of the
likely changes in the environment as a result
of the development.
Impact predictions are made according to
the Baseline studies.
5. EXTENT/LOCATION : The environmental
impacts are different in various locations.
Magnitude : Estimating the magnitude of
the impact is of primary importance. It is
expressed in terms of relative severity such
as major moderate or low severity.
6. Duration : Impacts depends upon the
duration. Some impacts may be short term,
such as the noise arising from the operation
of equipment during the construction.
Timing : Impacts arising from all of the life
cycle of the project should be considered
( ie, during construction, operation and
decommissioning). some impacts will occur
immediately, while others may be delayed,
sometimes by years.
7. METHODS FOR PREDICTING THE
CHARACTERISTICS OF IMPACTS
Professional judgment
Quantitative mathematical models
Experiments and physical models
Case studies
8. 1. Professional judgement
Predictions should be made by specialists, who
are familiar with the type of proposal, the
geographic region etc.
2. Quantitative mathematical models
A number of models are used to predict certain
types of impacts. Some of them are;
Air dispersion models to predict emissions and
pollution concentration at various locations
resulting from the operation of a coal-fired power
plant.
9. Hydrological models to predict changes in the
flow regime rivers resulting from the
construction of a reservoir.
Ecological models to predict changes in
aquatic biota resulting from discharge of toxic
substance.
3. Experiments and physical models
Experiments are carried out to test and
analyse the effects of project-related activities
10. Experiments can be undertaken directly in the
field or under laboratory conditions.
Physical models are used to predict the
behavior and effects of the project.
4. Case studies
Reviewing case studies of projects in similar
environments and the comparisons will be very
useful for predicting the impacts.
11. Nature of Impacts
Positive impacts
Negative impacts
Positive impacts : They are the beneficial
impacts that are considered to represent an
improvement to the baseline or introduces a new
desirable factor.
Eg: Employment opportunities
12. Negative impacts : An impact that is considered
to represent an adverse change from the baseline
or introduce a new undesirable factor.
Eg: Environmental pollution
Primary and Secondary impacts
Primary Impacts
Also known as Direct impacts that result from a
direct interaction between a proposed project
activity and the receiving environment.
13. Typical examples of direct impacts are;
- loss of wetlands caused by agricultural
drainage
- Destruction of habitat caused by forest
clearance
Secondary Impacts
Also known as Indirect Impacts
Secondary impacts are the impacts that are
usually less obvious, occurring later in time.
14. Examples are;
- The spread of Malaria as a result of drainage
schemes which increases standing water and there
by create new vector habitat
- Bio accumulation and Bio magnification of
contaminants in the food chain through take up of
agricultural pesticides
15. Impact on physical social and biotic
Environment
IMPACTS ON BIOTIC ENVIRONMENT ARE;
Degrades essential life support systems
Adversely affects ecological integrity
Loss of biodiversity
Unreasonably degrades the quality of life where
people live
16. Economic Impacts
Duration of construction and operation
Raw materials and other input purchases
Social Impacts
It includes changes in one or more of;
People’s livelihood
cultural including values and spiritual beliefs
17. lntrusion of outsiders
levels of health, education and physical
well-being
Loss of native culture
over crowding
