Environmental impact assessment procedure: A new approach based on fuzzy logic

The information related to the different environmental impacts produced by the execution of activities and projects is often limited, described by semantic variables and, affected by a high degree of inaccuracy and uncertainty, thereby making fuzzy logic a suitable tool with which to express and treat this information. The present study proposes a new approach based on fuzzy logic to carry out the environmental impact assessment (EIA) of these activities and projects.Firstly, a set of impact properties is stated and two nondimensional parameters — ranging from 0 to 100 —are assigned, (pi) to assess the value of the property and (vi) to assess its contribution to each environmental impact. Next, the impact properties are described by means of fuzzy numbers pi― using generalised confidence intervals. Then, a procedure based on fuzzy arithmetic is developed to define the assessment functions v̅ = f(p  ̅) — conventional mathematical functions, which incorporate the knowledge of these impact properties and give the fuzzy values vi― corresponding to each pi―. Subsequently, the fuzzy value of each environmental impact V  ̅ is estimated by aggregation of the values vi―, in order to obtain the total positive and negative environmental impacts V+― and V−― and, later — from them — the total environmental impact of the activity or project TV―. Finally, the defuzzyfication of TV― leads to a punctual impact estimator TV(1) — a conventional EI estimation — and its corresponding uncertainty interval estimator {(δl(TV―),δr(TV―)}, which represent the total value of the environmental impact caused by the execution of the considered activity or project.