Spatio-temporal analysis of the impact of quarry material extraction on land surface temperature: a case study of Anambra East L.G.A

Abstract

Quarrying has emerged as a leading land-use in the Anambra East Local Government Area (LGA) following the massive urbanization and infrastructural development in the state of Anambra. Although economically important, the activities have caused serious ecological changes especially in terms of thermal environment of land surface. This research paper presents a spatio-temporal assessment of the effect of the quarrying on the Land Surface Temperature (LST) in Anambra East LGA. It will measure the increase in the size of the quarrying locations and determine the thermal reaction of the landscape that follows. The study makes use of multi-temporal satellite images of the Landsat 5 TM, 7 ETM+ and 8/9 OLI/TIRS sensors. The Maximum Likelihood Algorithm was applied to find the change between vegetation and quarrying/bare land by means of the Land Use Land Cover (LULC) classification. The Thermal Infrared (TIR) bands were used to retrieve LST and it was corrected by the land surface emissivity. The correlation analysis was done statistically to establish how the relationship existed between the Normalized Difference Vegetation Index (NDVI) and surface temperature. A preliminary survey shows that there is a substantial increase in the quarrying operations, which are mostly located in the Aguleri and Umueri axes. There is a high positive relationship between the transformation of land to quarrying locations and the appearance of the thermal hotspots. Statistics indicate that LST in quarrying areas is always greater (around 4 ^oC to 8 ^oC) than in the adjacent vegetation cover. The loss of the green lung in the LGA has resulted in the emergence of localized Surface Urban Heat Island (SUHI) effect, which is decreased evapotranspiration and high sensible heat flux. The paper shows that localized climate warming is mostly caused by unregulated quarrying in Anambra East. These results underscore sustainable mining and compulsory reclamation of land and inclusion of thermal environmental monitoring into the environmental impact assessment (EIA) systems of the states as the most appropriate action to curb the ecological degradation in the long term.