CAUSATIVE FACTORS OF URBAN SPRAWL IN THE HOMAGAMA DIVISIONAL SECRETARIAT DIVISION

Abstract

Urban sprawl is the unplanned outward expansion of cities towards suburban areas, which often disrupts natural landscapes and resources. Hence, various causative factors contribute to this continuous expansion in suburban areas. Among them, population and road networks play a crucial role because of high automobile dependency and a liveable residential environment in suburban areas. Accordingly, this study aims to investigate the causative factors of urban sprawl in the Homagama Divisional Secretariat Division (1992-2022). To achieve this objective, the satellite images in 1992, 2007, 2017, and 2022 were downloaded from Google Earth Pro, using a 1:20,000 grid reference, and digitized the entire buildings. The road network data for 1992, 2007, and 2017 were collected from the Urban Development Authority (UDA) in Sri Lanka. Moreover, the road network data in 2022 was downloaded from the "Open Street Map" database utilizing the OSM tool in QGIS. Population density maps for 2000, 2007, 2017, and 2020 were downloaded from the "Worldpop" data source. Furthermore, the linear buffer zones with a 1,000 m radius were used to identify the buildings along with primary and secondary roads. As the result, population densities have gradually increased due to migrations of middle- and low- income individuals who cannot afford to live near the Central Business District (CBD) and opt for areas with somewhat developed infrastructure located further from the CBD. Consequently, some apartment complexes are mainly concentrated in Panagoda, Homagama, and Kahathuduwa. Many people have considered purchasing apartments rather than constructing their own houses. The correlation revealed a positive relationship (0.9962) between the population densities and building densities. In particular, the buildings, along with primary and secondary roads, gradually increase by improved accessibility and connectivity. This has further exacerbated sprawl in the study area. Moreover, this trend results in a linear pattern of buildings along these roads, particularly showcasing the growth of commercial buildings rather than residential buildings. According to the findings, it is essential to implement a sustainable urban development master plan to address the social, economic, and environmental challenges arising from high automobile dependency and competition for land acquisition.