Integrating knowledge-based multi-criteria evaluation techniques with GIS for landfill site selection: A case study using AHP

A major challenge in most growing urban areas of developing countries, without a pre-existing land use plan is the sustainable and efficient management of solid wastes. Siting a landfill is a complicated task because of several environmental regulations. This challenge gives birth to the need to develop efficient strategies for the selection of proper waste disposal sites in accordance with all existing environmental regulations. This paper presents a knowledge-based multi-criteria decision analysis using GIS for the selection of suitable landfill site in Ado-Ekiti, Nigeria. In order to identify suitable sites for landfill, seven factors - land use/cover, geology, river, soil, slope, lineament and roads - were taken into consideration. Each factor was classified and ranked based on prior knowledge about the area and existing guidelines. Weights for each factor were determined through pair-wise comparison using Saaty’s 9 point scale and AHP. The integration of factors according to their weights using weighted index overlay analysis revealed that 39.23 km² within the area was suitable to site a landfill. The resulting suitable area was classified as high suitability covering 6.47 km² (16.49%), moderate suitability 25.48 km² (64.95%) and low suitability 7.28 km² (18.56%) based on their overall weights.