Impact of Landuse change on Urban Thermal Variance in Umuahia Urban, Nigeria: a Remote Sensing-based Approach

Abstract

Urbanization is directly related to changes in land surface temperature (LST). However, little is known about the spatial and temporal impact of urbanization on Urban Thermal Variance (UTV) in Umuahia. To this end, we quantified the spatiotemporal associations of UTV intensity between 1986 and 2017. We calculated LST change by using a land-use change map and computed the level of vegetation coverage based on the Normalized Difference Vegetation Index (NDVI), and the Urban Thermal Field Variance Index (UTFVI). In so doing, we could determine the ecological index from multi-temporal Landsat data. Results showed that, at the expense of other types of land cover, the built-up portions of the study area were progressively increasing in surface area with a concomitant increase in temperature. The transfer matrix developed in this study reveals that within the 31-year period there was a transformation of about 59.88% and 8.23% from vegetation and bareland, respectively, to built-up cover. The spatio-temporal distribution of surface temperature showed that the built-up areas recorded the highest annual mean temperatures of 21.50^oC in 1986, 22.20^oC in 2001, and 26.01^oC in 2017. Results of the UTFVI showed that more areas were undergoing deteriorating ecological change and imbalances, thus leading to an increase in the area affected by the strong heat island phenomenon, which accounted for 0.065% of the total study area in 1986, 1.02% in 2000, and 32.91% in 2017. We concluded that urbanization has increased the overall surface temperature of the city. However, owing to the re-location of the city’s main market, there has been a decline in UTFV in the vicinity of the city centre. The research findings indicate that the implementations of effective plans to mitigate the heat island effects are imperative for the promotion of sustainable urban development.