The effect of green spaces on the urban thermal environment during a hot-dry season: a case study of Port Harcourt, Nigeria

Abstract

Improving the planning and management of urban green spaces can cause a drastic reduction in land surface temperature (LST). This research explored the geospatial techniques in assessing the effect of green spaces on the thermal environment of Port Harcourt, Nigeria during a hot-dry season. In this study, the normalized difference vegetation index (NDVI) and soil-adjusted vegetation index (SAVI) were employed to investigate the effects of vegetation distribution of urban green spaces on the urban thermal environment. LST maps were retrieved from the Thermal Infrared Sensor data of Landsat 8 acquired on 27 December 2018, while urban green spaces were extracted from high-resolution Google Earth Pro imagery. The results showed that a strong negative relationship exists between NDVI and LST, as well as between SAVI and LST which showed that urban green spaces have proven to have substantial cooling effects on the urban thermal environment within the study area. Results further revealed that increasing the area of green spaces to 28.67 ha and above will ensure the attainment of a stronger Park Cooling Intensity (PCI) effect. On the other hand, green spaces which are 8.28 ha or less have a lower PCI effect. The shape (perimeter/area) of green spaces has proven to have a negative correlation with the PCI effect. Green spaces with near-circular configurations will produce a stronger PCI effect. The role of urban greenery in mitigating high discomfort experienced in urban environments is crucial to urban planners and managers in the design of green spaces with a high cooling effect.