Analyzing lead time for flood early warning system in the upstream Citarum River

Abstract

The Citarum River is a staple water source for the people of West Java, irrigating rice fields in West Java, generating electricity in Java and Bali, supplying water to Jakarta, and operating hydroelectric dams. West Java is prone to flooding because of the concave topography of the Upper Citarum. Floods in Majalaya and Sapan are typically of short duration, with water levels increasing rapidly. Therefore, implementing a predictive early warning system is essential for effective flood control. This study examines lead times utilizing Global Satellite Mapping of Precipitation (GSMaP) data, water levels, and discharge information to provide Majalaya and Sapan communities with early flood warnings and enable timely evacuations. The analysis reveals that Majalaya’s lead time is often less than an hour (with 76% incidence and 24% risk), while Sapan's lead time is commonly less than four hours (with 86% occurrence and 14% risk). Utilizing effective lead times enhances the preparation before a flood in the study area. Given the importance of pre-flood evacuation lead times, this research can inform the development of early warning systems in Indonesia, particularly in Majalaya and Sapan.