Modelling the dynamics of flood overflow and its impact on the Ciliwung river basin

Abstract

Background: Flooding in the Ciliwung River border area, Jakarta, is caused by interactions between natural and human-induced factors. Jakarta's population grows by 1.11% per year, while urbanization increases by 2.7% per year, leading to 48.41% of land being used for housing, including in critical watershed areas. The Ciliwung watershed narrows by 0.65% annually, further aggravated by land subsidence at 2.75% per year. Extreme rainfall, reaching 150 mm, exacerbates flood vulnerability. Methods: This study employs the System Dynamics (SD) approach to model flood overflow dynamics, focusing on watershed narrowing due to land conversion into illegal settlements, increased rainfall, and land subsidence. The research applies SD by mapping causal relationships through a Causal Loop Diagram (CLD) and simulating scenarios, including Business as Usual (BAU) and mitigation strategies such as urbanization control, river normalization, and land rehabilitation. Findings: The research findings emphasize the need for integrated policies that combine land conversion restrictions, improving water absorption infrastructure, and strengthening river normalization programs. The developed SD model provides a dynamic framework for understanding the interdependence of natural and human factors, so that it can be the basis for sustainability-based flood mitigation planning in dense urban areas such as Jakarta. Conclusion: The analysis highlights the need for more detailed data to better understand flood-causing mechanisms, as population decline may help reduce flood risk through proper watershed land use, while natural factors like rainfall and land subsidence remain difficult to control. Despite its limitations, the System Dynamics (SD) model effectively maps flood risk factors and can be improved for more accurate mitigation planning. Novelty/Originality of this article: The novelty of this research lies in the application of SD modelling to dynamically assess the interplay between natural and anthropogenic factors in flood risk, offering a sustainability-based framework for urban flood mitigation planning in Jakarta.