Planning Implications of Urban Heat Island Effect in Mombasa

Abstract

Empirically, the Urban Heat Island Effect (UHIE) is a resultant of the reverberation consequences of climate change and urbanization within the built environment where hotter temperatures are acutely experienced in cities than their surrounding areas. Sadly, little is known to influence and prioritize the planning for cooler coastal cities of the tropical sub-Saharan Africa as they rapidly expand in both population size and built-up landscapes whilst simultaneously decline in green vegetation. From a spatial and temporal perspective of the sea-island of Mvita in the coastal city of Mombasa, the primary aim of the study was to empirically examine the planning implications of urban heat island effect. A subsidiary aim of the study was to propose planning interventions to enhance the mitigation of urban heat island effect in Mombasa. The study heavily depended on literature review on Earth Science; hot season diurnal satellite remote sensing for 1992, 2002 and 2022 and Geographic Information Systems (GIS) methodological approaches and over a 30-year (1990-2021) weather and climatology assessment. It utilized the proportionate stratified random sampling and 30-size rule of thumb to engage one-on-one with 68 sampled household participants and 30 sampled users of open public spaces. A visual survey and in-person interviews with 6 key informants — an urban planner, architect, public health and medical practitioner, urban climate change expert, environmental officer and a national environmental authority representative — were done. Results indicated that Mvita is a concrete jungle with a high relative humidity; more impervious surfaces, larger thermal capacity materials; less vegetation coverage; increasing vehicular, industrial, residential and commercial waste heat; moderate urban geometry and low air-conditioning systems in exposing UHIE. It is now a hotbed of hazardous land surface temperatures more than its ambient air temperatures at 2m due to its changing shift in socio-cultural, economic and political controlling interests over centuries. Economic impacts and environmental impacts of UHIE possessed a high sensitivity rating while the social impacts of urban heat islands institutional impacts of UHIE had a moderate sensitivity rating. UHIE has been broached broadly in affiliated policy guidelines, laws and regulations and institutions for mitigation in Mombasa and Kenya. Limited empirical evidences and lack of standardised health data and information systems with the urban thermal environment remains a cross-cutting challenge. Top-five prioritized heat mitigation and heat management solutions enveloped retrofitting of green walls, façades and building roofs; a green aeration and ventilation corridors programme; an urban micro-forestry programme for public parks, open spaces, residences and vacant plots; a suitable urban geometry for better wind flow and developing an urban heat resilience policy handbook. Recommended actions amounted to the establishment of an urban climate laboratory with cross-disciplinary expertise; fair funding; linking resilience theory with collaborative planning theory; virtual modelling via urban digital twin; better heat early warning and monitoring systems; heat action and heat response plans accounting provision of cooling centers; community urban heat island mapping campaigns and publication of the Kenya Spatial Biodiversity Atlas. When replicated, they can diversly serve for broader and positive social, economic, environmental and institutional ramifications — for theory, literature, methodology, policy, design, practice, monitoring, public awareness and dissemination and conservation of marine coastal ecosystems — on mitigating UHIE.