ASSESSMENT OF CHANGES IN MAXIMUM DAILY RAINFALL AND THEIR IMPACTS ON DESIGN FLOODS AND FLOW DURATION CURVES IN THE CILIWUNG AND CISADANE RIVER BASINS

ANALISIS PERUBAHAN CURAH HUJAN HARIAN MAKSIMUM TERHADAP BANJIR RANCANGAN DAN KURVA DURASI DI DAS CILIWUNG DAN CISADANE

Abstract

Climate change alters global climate variability and affects extreme rainfall patterns, with direct implications for civil engineering and water resources infrastructure. The Ciliwung and Cisadane River Basins, as major hydrological systems in the Greater Jakarta area, serve as representative regions impacted by these changes. This study aims to analyze trends in maximum daily rainfall in both basins and assess their implications for hydrological planning through design rainfall and Intensity–Duration–Frequency (IDF) curves. Maximum daily rainfall data were obtained from six BMKG stations: South Tangerang (Climatology South Tangerang, Soekarno–Hatta Meteorology, Budiarto Meteorology) for the period 1990–2020, and the Ciliwung Basin (Citeko Meteorology, West Java Climatology, Tanjung Priok Maritime Meteorology) for the period 1992–2022. Trend analysis was conducted using the Mann–Kendall test and Sen’s Slope estimator, while design rainfall was determined using the Log Pearson Type III distribution. The results indicate that in South Tangerang, trends are variable (both positive and negative) but statistically insignificant (Z-value ±1), whereas in the Ciliwung Basin, an increasing tendency is observed with positive median Q values across the three stations. The 100-year return period design rainfall reaches 206.25 mm in South Tangerang and 230 mm in Citeko. This difference reflects the influence of urbanization in South Tangerang and the role of topography and basin conditions in the Ciliwung Basin. The findings underscore the necessity of adapting drainage design, flood control systems, and basin-based water management policies to evolving climate dynamics.