The essence of EIA is predicting future environmental conditions, either with the proposed development or without. A comparison of the two predicted situations is also often made with the present. Prediction is the process of determining the nature and extent of the environmental changes that will result from a proposed activity. From an examination of the methods available for predicting different effects, the following main “types” of methods could be identified: physical models, experimental methods, and mathematical models.
Physical models, illustrative or working scale models constructed to represent the environment, may include visual representations of the environment by picture, photograph, film, or three-dimensional model and working models of the environment using, for example, wind tunnels or wave chambers.
Experimental methods, practical field or laboratory work, include field experiments, in which tests are carried out at the proposed site, and laboratory experiments, in which tests are carried out in the laboratory in conditions simulating the environment.
Mathematical models, in which the relationship between the cause and effect is represented by one or more mathematical relationships, may be either empirical (black box) models, where the relationships between inputs and outputs are established from statistical analysis of observations 98