An urban flood-risk assessment of South Jakarta, Indonesia: A methodological approach through frequency ratio, receiver operating curve and analytic hierarchy process

The main objective of this research is to conduct an urban flood-risk assessment approach for South Jakarta, Indonesia. Flood susceptibility was modelled using the frequency ratio (FR) method and validated with the receiver operating characteristic–area under the curve (ROC–AUC). Vulnerability was assessed using the analytic hierarchy process (AHP) across four domains: physical, economic, environmental and social. We used high-resolution spatial data (1:25 000) and a historical flood inventory to produce rapid, urban-scale risk information where conventional datasets are limited. The susceptibility map shows three classes: low, medium and high; the combined risk map indicates that most of the study area is at medium risk (108.64 km2, or 74.550%), low (37.08 km2 or 25.447%) and high (0.004 km2 or 0.003%). Vulnerability analysis identifies residential areas, critical infrastructure and key service zones as the most exposed elements. Susceptibility, vulnerability and risk are the three essential parameters incorporated into the spatial planning analysis to ensure comprehensive evaluation. The findings identify protection zones with particular risk levels, which require targeted mitigation strategies for any future development initiatives. Furthermore, this study highlights that the integration of FR, ROC–AUC and AHP provides reliable and operational flood-risk assessments that can be effectively incorporated into spatial planning and development policies in data-constrained urban settings. Contribution: This study presents an innovative and practical framework for urban flood-risk assessment, combining FR, ROC–AUC and AHP to evaluate flood susceptibility and vulnerability in South Jakarta, Indonesia. Leveraging high-resolution geospatial data at a detailed 1:25 000 scale, it addresses critical data gaps and equips policymakers with actionable tools to integrate risk sensitive strategies into urban spatial planning for further mitigation. The findings, revealing 74.55% of the area at medium flood risk, set a benchmark for advancing disaster resilience and sustainable urban development, offering valuable applications for other rapidly urbanising, data-constrained regions globally.