Abstract
Abstract. Iloilo City, a highly urbanized city in the Philippines, experiences intensified climate change impacts due to the Urban Heat Island (UHI) phenomenon, one of which is the significant increase in temperature. To mitigate UHI, recent studies investigated the cooling effect of water bodies due to its higher rate of evapotranspiration compared to green spaces. This study aims to spatiotemporally assess the Urban Cooling Island (UCI) effect of Iloilo River and adjacent wetlands on the surrounding microclimate using geospatial techniques. Landsat images were processed to generate land surface temperature (LST) and land cover layers of the study area for the years 1994, 1998, 2003, 2005, 2013, 2016, and 2019. UCI Scale (influence range of the cooling effect), Temperature Difference (difference in temperature between water space and the area within the UCI scale), and UCI Intensity (temperature gradient within the UCI scale) were calculated using multiple-ring buffers with 50-m interval to quantify variations in cooling effect of the water space at distinct surrounding regions over a long time period. Results of the study show that wetland area has a weak negative relationship with the UCI indices which could mean that cooling effect is not solely dependent on wetland size, while moderate to very strong negative correlations were calculated between temperature difference and precipitation (r = −0.48 to −0.82). Furthermore, rapid expansion of built-up areas at different sections along the river have resulted to reduced UCI scale (r = −0.37 to −0.75) and stronger cooling intensity (r = 0.55 to 0.84).
Highlights
Increasing rate of urbanization, considered as one of the indicators of economic growth in the Philippines, has led to detrimental effects on the urban thermal environment
In contrast to urban heat island (UHI), urban cooling islands (UCI) such as green and water spaces are areas within the urban regions with cooler surface temperatures compared with their neighboring landscapes (Ca et al, 1998)
Its landscape shape index increased from 4.99 to 5.75 which indicate that the overall shape of the water space became more complex
Summary
Increasing rate of urbanization, considered as one of the indicators of economic growth in the Philippines, has led to detrimental effects on the urban thermal environment. The prevalence of impervious surfaces such as concrete and asphalt pavements, coupled with heightened anthropogenic heat emissions from vehicles and air-conditioning systems, has resulted to generally hotter temperatures in highly urbanized cities as compared to its surrounding rural areas. This substantial difference in temperature between urban and rural areas is one of the manifestations of the urban heat island (UHI) phenomenon (Tiangco et al, 2008). In terms of cooling efficiency, water bodies such as rivers, streams, reservoirs, and lakes are relatively more effective than green spaces due to its higher rate of evapotranspiration and thermal capacity (Sun et al, 2012)
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