Characterizing the extreme and heavy rainfall events in the Serang catchment, Indonesia using satellite data

This study analyses the characteristics of heavy and extreme rainfall in the Serang Watershed, Kulon Progo, during 2019-2021 by combining observational rainfall data with GSMaP satellite data. Intensity, duration, and frequency (IDF) analysis was used to understand rainfall dynamics in a tropical region influenced by the monsoon and the topography of the Menoreh Hills. The results show a bimodal rainfall pattern with peaks in March and December, while June-August is very dry. Short-duration extreme rainfall (>30 mm/hour) occurs mainly at the beginning and end of the rainy season, related to convective and/or orographic processes. Stations at high elevations record greater rainfall and higher rainfall intensity than those at low elevations. Comparison with GSMaP shows a significant positive bias in rainfall duration and total rainfall, as well as low temporal correlation due to satellite limitations in detecting local convective rainfall. These findings suggest that hydrological risks in the Serang Catchment are more influenced by the intensity and duration of extreme rainfall than by total annual rainfall. Integration of bias-corrected observational and satellite data is needed to improve the accuracy of extreme rainfall estimates and to support flood mitigation, erosion control, and watershed management.