A new method for evaluating the synergistic effect of urban water body and vegetation in the summer outdoor thermal environment

Abstract

In the context of climate change, urban blue-green infrastructure (UBGI), consisting of water and vegetation, has received extensive attention for urban microclimate improvement. However, the detailed quantification of spatial relationships between blue and green infrastructure elements has not been conducted about the thermal environment. To study the synergistic effect of water and vegetation, this paper conducted the field measurement and questionnaire on typical UBGI in Tianjin, China. The spatial characteristics and the current situation of the thermal environment of UBGI were obtained, and the thermal demands of UBGI users were established based on the wet-bulb globe temperature (WBGT) and heat index (HI). The results of the study indicated that the synergistic effect of the water body and vegetation was the most significant at a distance of 6 m from the water body. In the condition of light airflow (wind speed ≤1.5 m/s), the different orientations relative to the water body had no significant difference in the thermal environment. Based on the quantification of spatial relationships, the conversion factors (cT and cRH) of the synergistic effect at different locations in UBGI were obtained. Furthermore, synergistic effect (SE) models of the thermal environment of UBGI were established according to the conversion factors. Meanwhile, the thermal comfort benchmarks for SE models were quantified (WBGT: 25.76–27.96 °C and HI: 24.98–27.25 °C). This study provides scientific guidance and reference for the planning and redevelopment of UBGI.