Flood risk monitoring and early warning system for informal settlements with GeoAI in South Africa

Informal settlements are defined as areas where people select an area, typically at the outskirts of urban areas, to occupy for residential purposes, either temporarily or permanently (Dubovyk et al., 2011; Muzondi, 2014). Though there is no universal definition of informal settlements, they are characterized by the use of land without formal approvals by authorities. According to UN-Habitat (2022), approximately 12,5% the world population reside in informal settlements. Informal settlements in South Africa represent a socio-economic challenges, driven by rapid post-apartheid urbanization, persistent spatial inequalities, just to mention a few (Marais et al., 2017). Across the country, informal dwelling prevalence varies significantly by province; ie., economic hubs like Gauteng (11%) and the Western Cape (11%) hold high proportions of informal households and mining hubs like the Northern Cape (12%) show substantial informal growth, contrasting with more rural provinces like Limpopo (3.0%) where traditional housing structures predominate (Stats SA, 2023). Sub-Saharan Africa region has the highest rate of urban informal settlements (Zerbo et al., 2020). A closer look at City of Tshwane Metropolitan Municipality in Gauteng, local housing responses reflect immense scale of urban migration (Moloisane, 2018). Assessments of local informal settlement strategies, such as evaluations of township expansions in Mamelodi, demonstrate that persistent poverty, as well as delivery bottlenecks have hindered complete formalisation under local housing plans (Moloisane, 2018). The municipality oversees approximately more than 200 identified informal settlements under its Upgrading of Informal Settlement Programme (UISP) framework, categorizing them into upgrade sites, and high-risk relocation sites. Despite ongoing municipal efforts to supply interim basic water to over 100 settlements, infrastructure backlogs leave many residents vulnerable to environmental risks (Marais et al., 2017; Moloisane, 2018). These settlements are located in hazardous areas, including floodplains, wetlands, which are attributed, to some extent to apartheid-era spatial planning and compounded by rural-urban migration and economic pressures (Gcabashe & Pillay, 2026; Broekman, Coetzee & Cilliers, 2025). Socio-economic and the high cost of formal housing in urban areas are the major contributing factors to informal settlement dwelling. Residents lack the necessary basic services, and the building materials used in the housing structures do not meet the requirements of formal housing, above all, they are usually situated in environmentally hazardous areas. In the context of climate change hazards, spatial configuration involving urban informality in combination with multiple sources of vulnerability limits flood risk reduction. Floods are a common event that drastically changes the landscape, resulting in significant harm to both property and life.