Integrated Approach to Siting Sanitary Landfill Using GIS, AHP, Geophysical and Geotechnical Investigations: A Case Study of Kwara State, Nigeria
The prevailing trend of waste disposal site in many parts of sub-Saharan Africa is detrimental to the environment on a long term. Waste disposal sites are randomly selected and frequently incinerated, releasing harmful gases which have negative impacts on the surrounding ecosystem and human life. The study area in Kwara State, Nigeria is a Microcosm of Africa’s unique challenge. The research is aimed at the determination of suitable landfill sites that engender environment sustainability. The proposed landfill sites were investigated using Geographic Information System (GIS), Geological, Geophysical and Geotechnical techniques as tools to aid the decision-making processes. To achieve the objectives, 2017 IKONOS Satellite imagery was used to identify geological features, soil, topography, land use, roads network, river, surface water, infrastructure and settlement. Twenty (20) vertical electrical soundings (VES) were conducted using the Schlumberger configuration for geophysical investigations. Three to four layers were deduced: Topsoil/laterite, clay, weathered basement, moderate to fresh basement. An integration of IKONOS satellite imagery, geology, geophysics and geotechnical data were modelled with Environmental geo-spatial model builder in ArcGIS 10.3 environment using Analytic Hierarchy Process (AHP). Weighted Linear Combination (WLC) and multi criteria analysis in which criteria such as distance from settlement, roads, highway, land use, water body, river, water table, elevation, and slope were used after geo referencing, reclassifying, weighting of criteria, data overlaid and finally suitability model map were developed. The whole area falls into two categories: moderately suitable (Sokoto2, Malete) and not suitable (Sokoto1, Oke Oyi). It is expected that soil improvement techniques such as geo-textile and geo-membrane can be used to improve sites which are not suitable for landfill sites.