Assessment of environmentally suitable sites for solid waste sanitary landfill using analytical hierarchy process (AHP) and GIS in Uyo and environs, South-South Nigeria

Abstract

Abstract Rapid urban growth in the Global South makes it harder to choose infrastructure corridors, especially in sensitive coastal basins. This study introduces a spatial decision-support framework tailored to local conditions. It combines the Delphi technique, Analytical Hierarchy Process (AHP), and Geographic Information Systems (GIS) to improve sanitary landfill site selection in Uyo and nearby areas in South-South Nigeria. The region sits on the highly permeable Benin Formation and gets heavy annual rainfall of 2,500 mm. Ten environmental experts participated in a three-round Delphi process to agree on key parameters, which were subsequently measured using a pairwise AHP matrix to ensure consistency (CR < 0.10). Hydrogeological factors, mainly Lithology and Soil Permeability (31.4%), were given the greatest weight, followed by infrastructure and proximity factors. Using Weighted Linear Combination (WLC), the spatial analysis showed a strong urban buffer effect: only 210.5 km 2 (9.2%) of the 2,289.41 km 2 area is classified as “Highly Suitable” for engineering, mostly in remote parts of Ikono, Ibiono, Uruan, and Etinan. The rest of the land is limited by required exclusion zones around growing peri-urban homes (1,000 m) and surface drainage networks (500 m). The model was checked with fifteen independent ground-truth points, showing an overall accuracy of 86.67% and a Cohen’s Kappa coefficient (ǩ) of 0.762, which means there was strong spatial agreement. The findings show that standard site selection methods often underestimate aquifer risks in tropical sedimentary areas. The protocol developed here offers a practical framework for infrastructure planning in humid, vulnerable regions with limited data.