Identifying impervious surface hot spots in Ho Chi Minh City using object-based classification and spatial statistics

Abstract

Impervious surface is often a primary indicator for urbanization. The rapid expansion of impervious surface area (ISA) can lead to a variety of environmental issues such as the change in local climate, urban heat islands, urban flooding, biodiversity loss, and the depletion of air quality. In this paper, satellite data from Landsat 5 TM, Landsat 8 OLI, and Sentinel-2 were employed to extract impervious areas in Ho Chi Minh City (HCMC) from 2009 to 2022 by integrating the object-based image analysis and Kernel density estimation method. Regarding spatial analysis, optimized hot spot analysis (OHSA) and emerging hot spot analysis (EHSA) were used to detect specific spatial distribution and spatio-temporal changes of ISA hot spots over the 12 years. Study results show the hot spots of ISA with 99% confidence interval increased considerably from 28,625 ha in 2009 to 44,400 ha in 2022. Through emerging hot spot analysis, many kinds of ISA hot spots including persistent, new, intensifying, sporadic, and potential hot spots were traced over time. New hot spots had a total area of 14,975 ha, located mainly in Cu Chi, Thu Duc city, whereas potential hot spots, which are likely to become new hot spots in the future, were over 28,000 ha, making up 19% of the study area. Thus, the results from this study can provide a preliminary prediction of ISA distribution for HCMC in the coming years.