Street's physical geometry and the cooling effect of waterbody of urban micro-climate in tropical region

Abstract

The thesis addresses the contributions of urban geometry under tropical climate in the Melaka city, Malaysia and their benefits toward optimum cooling effect of water body modification. The aim is to examine quantitatively the potential of the cooling effect from combination of water bodies and street geometries with the development of comfortable microclimate conditions at street level in the city environment. Main methodologies phases which is field measurement were conducted and computer simulations were developed in order to achieve the aim and objectives of study. Environmental Visual Image Microclimate software (ENVI-met Ver. 4.0) was used to predict the impact of modification according to the proposed hypothetical urban geometries were simulated with various street aspect ratio (building’s height / street’s width) where the ratio is equal to 1, more than 1, and less than 1, and river width equal to 18, 36, and 54 meters. The proposed urban settings in Melaka city that resulted from the combination of the various streets and river width were modelled on four different orientations, North-South, East-West, Northeast-Southwest and Northwest-Southeast, while a total of 36 different urban geometries were evaluated. The model was successfully validated through the correlation of measured experiments and computer simulation which reliable enough to present the actual urban microclimate condition of Melaka river area. The outdoor thermal comfort was assessed based on the Physiological Equivalent Temperature (PET) as reference to evaluate modification benefits towards outdoor comfort level. It is revealed that the existing variation in temperature between the different urban locations in the Melaka river area was due to the influence of their street geometrical characteristics. Overall, the improvements of thermal comfort via the addition of water bodies is very minimal when compared to the improvements brought by aspect ratios. The highly humid climate in Malaysia and the low wind speed conditions is the reason for this occurrence. The conclusions point out besides the necessity of street geometry, water body cooling effects can be implemented as additional guide lines in urban design to keep the external microclimate conditions in comfort range.