GEOSPATIAL ASSESSMENT OF URBAN HEAT ISLAND IN OWERRI, SOUTH EAST, NIGERIA

Abstract

This study used geospatial technology in assessing the spatio-temporal dynamics of Urban Heat Island in Owerri, South East, Nigeria. Landsat TM, ETM+ and OLI/TIRS imageries acquired during the dry season were used in the study to cover for the period (1986 – 2016). Change detection analysis showed that between 1986 and 2000, the built-up areas in the study area gained 20.12 km2 while vegetation lost 3.17 km2. On the other hand, bare soil and water bodies lost approximately 16.91 km2 and 0.04 km2 respectively. However, it was shown that between 2000 and 2016, the built-up areas gained 50.61 km2 while vegetation lost 50.30 km2. Also, bare soil witnessed a loss of 0.95 km2 while the water body gained 0.64 km2. Accuracy assessment performed showed that there were high degrees of conformity between classified maps of 1986, 2000 and 2016 and ground-truth reference points. Regression analysis depicted that there exists strong positive relationship between LST and Urban Index (UI), with correlation coefficient (R) values of 0.83, 0.91 and 0.80 for 1986, 2000 and 2016 respectively, except for Normalized Difference Water Index (NDWI) (with correlation coefficient (R) values of -0.83, -0.91 and -0.80 for 1986, 2000 and 2016 respectively) and Normalized Difference Vegetation Index (NDVI) (with correlation coefficient (R) values of -0.92, -0.89 and -0.88 for 1986, 2000 and 2016 respectively) that exhibited strong negative relationships. The temporal LST distribution between 1986 and 2000, showed that the mean LST increased by 7.41 ºC and by 4.51 ºC between 2000 and 2016, Urban growth had played a dominant role in the temperature profile in the study area causing Owerri City centre to be relatively warmer than the surrounding suburban areas, indicating the existence of UHI in the study area. The varying degrees of UHI intensities at the chosen urban and suburban stations in the study area showed that the mean UHI intensity had increased from 1.53 ºC in 1986, 4.2 ºC in 2000 to 5.27 ºC in 2016.