Assessment Of Surface Daytime Urban Heat Island Dynamics In Onitsha From 2010-2023

Abstract

This study assessed the surface daytime urban heat island and land use/land cover change dynamics
in Onitsha from 2010 to 2023. The objectives of the study include the determination of land surface
temperature, the magnitude of UHI, and measures to mitigate UHI in the study area. The research
design adopted in this study is the survey design. Multitemporal Landsat ETM+ and OLI images
were obtained at 7-year intervals for 2010, 2017, and 2024, respectively. The images obtained
were classified using the supervised classification techniques. The result showed that LST varies
from a range of 23.8 – 33.1 oC in 2010, to 24.9 – 33.1 oC in 2017, and 25.4 – 38.8 oC in 2024. By
2024, extreme heat dominated much of the city, given a dramatic intensification of high LST values
across Onitsha compared to 2010 and 2017. For the western part of the city, termed the coolest,
the extent of this coolest range has further contracted compared to 2017 (21.8–24.8°C) and 2010
(21.4–23.7°C), with more areas near the river shifting into the 25.4–28.7°C range, indicating
continued warming even in this thermally modified zone. The determined UHI magnitude revealed
a UHI magnitude of 1.9°C in 2010, which increased to 2.4°C in 2017 and further grew to 2.6°C
by 2024 though ANOVA revealed that the observed variations in LST across the years are not
statistically significantly different. The progressive increase highlights the intensification of the
UHI effect in Onitsha, driven by rapid urbanization, population growth, and land use changes.
The study recommends the setting up of afforestation programs to intentionally modify the
microclimate of the Onitsha urban area, check urban sprawl, and ensure continuous monitoring
using remote sensing techniques.