Floods in Jakarta region is an annual problem. Overflow of Ciliwung River is one of rivers that causing floods in Jakarta. Katulampa Post/Weir is an early warning system of flooding occurrence in Ciliwung River before entering the city. The discharge at Katulampa weir measured by using manual or conventional system. This paper presented study result of frequency analysis of maximum dischargeat Katulampa Weir. The outcome will be utilized as the basis in the prediction of design-flood discharge for flood management plan. Flood often occurs in Ciliwung River which detected at Katulampa Weir. This study is preceded by analyzing the discharge and precipitation data using approach hydrology and statistics. Based on the calculated discharge by using rational method, correlation between the discharge at Katulampa Weir and upstream rainfall of Ciliwung River showed linear trendline. The study showed that Gumbel distribution is the best method in calculating design-flood discharge.
Based on ratios among Katulampa Weir and Panus Bridge post Depok, Mean Absolute Percent Error (MAPE) on Katulampa Weir has large error percentage compare to Panus bridge post Depok. Hence, conventional water level recording system in the Katulampa Weir is not effective to minimize the error in data recording. Design-flood discharge of 1078, 62 m 3/s; 1177, 61 m 3/s; and 1276, 61 m 3/s was obtained using maximum discharge analysis with 25, 50 and 100 years return periods and 10% risk level. It will be utilized to design flood control structures.