Projected urban development, changing ‘local climate zones’ and relative warming effects in Colombo, Sri Lanka

Abstract

Colombo is rapidly developing. This factor is further highlighted by the projected urban growth outlined by the Sri Lanka Urban Development Authority, “Zoning Plan 2020 for the City of Colombo”. The background climate of Colombo is found to be affected by the ‘Urban Heat Island’ (UHI) phenomenon. Together with the projected urbanisation, ensuing changes to land use patterns and building morphology, local climate changes are deemed to make the already barely-tolerable thermal conditions within the city more intolerable. This study quantifies and compares the local warming effects of the projected development of the city in relation to the existing conditions. It employs a land-use / local climate classification system defined as Local Climate Zones (LCZ). Likely local warming effects of the current and the projected urban fabric, classified according to LCZs are simulated using the Surface Heat Island Model. The data is presented as a detailed comparison of the two stages, highlighting the LCZ changes that will most affect the Urban Heat Island intensity of the city. Results and analysis reveal that almost all LCZs that transform to a higher density typology elevate the UHI intensity significantly. The typologies most affected are LCZ7 – Lightweight low-rise and LCZ8 – Large low-rise areas of the current urban fabric.