Climate Change Adaptation: Prioritising Districts for Urban Green Coverage to Mitigate High Temperatures and UHIE in Developing Countries

Abstract

Urbanisation and the increasing population contribute to the occurrence of the well-documented phenomena of urban heat island effect (UHIE). Heat-related problems have become a global issue as prolonged exposure to extreme high temperatures increased the percentage of mortality and morbidity in cities worldwide. The purpose of this study is to prioritise urban areas that are at high risk for heat-related incidents, particularly in Cairo Governorate, Egypt. It also intended to investigate the implementation of urban green coverage (UGC) strategies such as green open spaces, trees, green roofs, and vertical walls. UGC would contribute to mitigating UHIE in developing countries. The methodology includes a review on the UHI problems, along with the cooling benefits the UGC can produce. In addition, the study adopts the Australian model developed by A. Norton et al., in 2015, which states that a high-priority area can be identified by the intersection of three factors: (1) high daytime/night-time surface temperatures (heat exposure), (2) most vulnerable sections of the society to extreme heat (vulnerability), and (3) zones with many users active outdoor (behavioural exposure). However, in Cairo City, it was difficult to assess the behaviour of population in outdoor public spaces. Therefore, the study follows “Crichton’s Risk Triangle” conducted by Morabito et al., 2015, to identify high-risk areas based on the intersection of three layers. The triangle’s three components are (a) high daytime/night-time surface temperatures (hazard), (b) total exposed population in a city (exposure), and (c) subpopulations at risk of being harmed during extreme heat (vulnerability). In the simulation, the risk assessment method simplifies the process of constructing the GIS database as it is composed of layering system. Hence, this study takes into account several vulnerability factors such as the distribution of the elderly and very young population and the deprivation index of Cairo districts. In the development of a heat-related vulnerability index (HVI) map for Cairo districts, it was done by overlayering the natural hazard layer (land surface temperature in summer) with spatial demographic data using GIS Software. Results of risk maps of Cairo were presented and showed normalised HVI values ranging between 0.0 and 1.0, which can be categorised into five risk levels (very low, low, moderate, high, and very high). Results also indicated that 13 out of the 46 districts in Cairo are at very high/ high risk, while only five districts have a very low-risk probability. Finally, the study develops a tool to map the population vulnerability to extreme heat events in Cairo city resulting from UHIE, which identifies high-priority risk areas that requires urgent intervention by applying more UGC as a significant action to mitigate UHIE in cities and adapt to climate change risks.