Linking the Reservoir Volume to the Flood Inundation Extent: A Multi-Dam Empirical Model for Indonesian Dam Safety

Indonesia rapidly expands its dam infrastructure to meet the water resource and development needs. This expansion, however, coupled with more extreme rainfall events due to the climate change, significantly increases the risk of catastrophic dam failures and downstream flooding. Existing studies of dam-break floods in Indonesia are typically limited to single-dam case analyses or theoretical models. Consequently, no comprehensive empirical model exists to predict the flood inundation from dam failures across varied locations or dam types, particularly for vulnerable earth fill dams. The present study addresses this gap by analyzing 12 representative dams across Indonesia, spanning various regions, reservoir capacities, and hydrological settings, to develop an empirical relationship between the reservoir storage volume and downstream flood inundation area. By integrating structural variables (e.g., dam height, storage area, reservoir capacity) with hydrological factors, an empirical multi-dam volume–area inundation model is derived applicable to overtopping and piping failure scenarios. The results demonstrate that the dam height and reservoir size strongly influence the flood extent, and the proposed volume–area model can reasonably estimate the inundation areas for different collapse scenarios. This is the first multi-dam empirical flood inundation model in the Indonesian context. The findings provide improved insight into the dam failure impacts and offer a practical tool to enhance the risk assessment, guide emergency response planning, and inform the national dam safety policy.