Analytical Study of Urban Heat Island Mitigation Through Green Infrastructure in Port Harcourt Metropolitan Area

The urban heat island effect in Port Harcourt metropolitan area, South South Nigeria, significantly elevates energy consumption, thermal discomfort, and health risks relative to surrounding peri-urban areas. This study analytically investigates the contribution of green infrastructure (urban forests, green roofs, bioretention gardens, and streetside vegetation) to urban heat island mitigation in Port Harcourt. A climate-terrain coupled analytical methodology was adopted, using land surface temperature data derived from Landsat 8 OLI/TIRS imagery (2015 to 2023) to quantify the spatial distribution and temporal trend of surface urban heat island intensity in Port Harcourt. Green infrastructure coverage was mapped from high-resolution satellite imagery using object-based image analysis. Correlation analysis and multivariate regression assessed the relationship between green cover density and surface temperature. Climate modelling using WRF-Urban evaluated the cooling potential of three green infrastructure expansion scenarios. Results indicate that the peak surface urban heat island intensity in Port Harcourt is 5.8 degrees Celsius above peri-urban reference temperatures during dry season periods. Each 10 percent increase in green cover in a 500 m radius is associated with 1.2 degrees Celsius surface temperature reduction. The tree canopy expansion scenario projects the greatest cooling benefit (peak reduction of 2.1 degrees Celsius) across the highest-intensity heat island zones. The study fills a research gap in urban heat island green infrastructure research for West African cities and recommends integration of green cover targets into Port Harcourt urban master plan revision.

Keywords: urban heat island, green infrastructure, Port Harcourt, urban microclimate, South South Nigeria