<![CDATA[The Katulampa Weir functions as a critical flood early warning structure for the Ciliwung River Basin, particularly for downstream areas in DKI Jakarta. Rapid land-use change in the upstream catchment has sharply increased the runoff coefficient, making effective weir management essential. This study evaluates the operational performance of the Katulampa Weir using existing infrastructure data, the applied rating curve, and adherence to Standard Operating Procedures (SOP). Results show that the weir spillway has historically discharged up to 629.968 L/s at alert level 1 (Siaga 1) without structural damage, and that strict SOP compliance yields an average flow travel time of 9 to 10 hours (ranging 6 to 12 hours) to downstream Jakarta. Analysis of five documented flood events between 2020 and 2025 confirms that discharge surges at the weir were consistently followed by downstream flooding within 6 to 12 hours, although flooding can also occur below alert level 1 due to accumulated rainfall. These findings demonstrate that the weir monitoring and reporting system provides downstream authorities sufficient lead time for coordinated emergency response, thereby reducing casualties and losses. Abstrak Bendung Katulampa berfungsi sebagai sistem peringatan dini banjir yang penting bagi Daerah Aliran Sungai (DAS) Ciliwung, khususnya kawasan hilir di DKI Jakarta. Perubahan tata guna lahan di hulu meningkatkan koefisien limpasan secara drastis sehingga pengelolaan bendung yang efektif menjadi penting. Penelitian ini mengevaluasi kinerja operasional Bendung Katulampa menggunakan data infrastruktur eksisting, kurva lengkung debit (rating curve), dan kepatuhan terhadap Standar Operasional Prosedur (SOP). Hasil studi menunjukkan bahwa saluran pelimpas mampu mengalirkan debit ekstrem hingga 629.968 L/dt pada status Siaga 1 tanpa kerusakan struktur, dan bahwa kepatuhan SOP menghasilkan jeda waktu aliran rata-rata 9 hingga 10 jam (berkisar 6 hingga 12 jam) menuju hilir Jakarta. Analisis terhadap lima kejadian banjir terdokumentasi periode 2020–2025 membuktikan bahwa lonjakan debit di Bendung Katulampa secara konsisten diikuti banjir di hilir dalam rentang 6 hingga 12 jam, meskipun banjir juga dapat terjadi di bawah status Siaga 1 akibat akumulasi curah hujan. Temuan ini menunjukkan bahwa sistem pemantauan dan pelaporan Bendung Katulampa memberikan waktu yang cukup bagi pihak berwenang di hilir untuk melakukan respons darurat secara terkoordinasi, sehingga mengurangi risiko korban jiwa dan kerugian.]]>
