Kinerja Sistem Pengendalian Banjir Serang Lusi Juana Menggunakan HEC-ResSim

Puspastyari Windamukti, Dr. Ir. Istiarto, M.Eng., IPU. ; Prof. Dr. Ir. Bambang Agus Kironoto

2026 | Tesis | S2 Teknik Sipil

Sistem Pengendalian Banjir Serang Lusi Juana (SELUNA) merupakan salah satu sistem pengendalian banjir multiwaduk yang kompleks di Provinsi Jawa Tengah, menghubungkan Sungai Serang dan Sungai Lusi di bagian hulu dengan Sungai Wulan dan Sungai Juana di bagian hilir melalui Pintu Pembagi Wilalung. Kompleksitas interaksi antarwaduk dan jaringan sungai, ditambah belum dilakukannya penelusuran banjir (flood routing) pada ruas-ruas sungai penghubung, menyebabkan evaluasi kinerja sistem ini masih terbatas, padahal Kabupaten Demak sebagai wilayah hilir tercatat mengalami 89 kejadian banjir sejak tahun 1998–2023, dengan debit puncak banjir pada 2024 mencapai 1.682,9 m³/s. Penelitian ini bertujuan mendapatkan karakteristik aliran banjir dan mengetahui kinerja Sistem SELUNA dalam mengendalikan debit banjir rencana kala ulang 100 tahun menggunakan perangkat lunak HEC-ResSim dengan metode penelusuran banjir Muskingum. Simulasi dilakukan pada dua skenario, yaitu Skenario A tanpa penelusuran banjir dan Skenario B dengan penelusuran banjir Muskingum, terhadap dua belas ruas sungai selama periode simulasi 52 jam. Parameter <!--[if gte msEquation 12]>K<![endif]--><!--[if !msEquation]--> <!--[endif]--> dan <!--[if gte msEquation 12]>X <![endif]--><!--[if !msEquation]--> <!--[endif]-->ditentukan berdasarkan panjang ruas, kecepatan aliran, dan morfologi sungai, menghasilkan tiga kelas nilai <!--[if gte msEquation 12]>X<![endif]--><!--[if !msEquation]--> <!--[endif]--> (0,20; 0,18; dan 0,15) yang menggambarkan ruas hulu-konektor waduk, ruas aluvial semi-meandering, dan ruas hilir-sungai pantai. Hasil simulasi menunjukkan reduksi debit puncak berkisar 0–78,85?n keterlambatan waktu puncak 0–39 jam, dengan rata-rata reduksi meningkat dari 4,87% pada kelompok = 0,20 menjadi 43,52% pada kelompok = 0,15, mengonfirmasi bahwa semakin kecil nilai <!--[if gte msEquation 12]>X<![endif]--><!--[if !msEquation]--> <!--[endif]--> semakin besar peran atenuasi tampungan sungai. Tetapi, periode simulasi 52 jam belum cukup menangkap debit puncak penuh pada beberapa ruas hilir karena waktu tempuh kumulatif Muskingum melebihi 36 jam, sehingga nilai reduksi pada ruas-ruas tersebut bersifat sementara. Penelitian ini menegaskan bahwa penelusuran banjir Muskingum memberikan kontribusi nyata terhadap kinerja Sistem SELUNA, khususnya dalam memberikan tambahan waktu respons bagi upaya peringatan dini di wilayah hilir.

The Serang Lusi Juana Flood Control System (SELUNA) is one of the complex multi-reservoir flood control systems in Central Java Province, connecting the Serang and Lusi Rivers in the upstream section with the Wulan and Juana Rivers downstream through the Wilalung Diversion Gate. The complexity of inter-reservoir interactions and the river network, combined with the fact that flood routing has not yet been carried out on the connecting river reaches, has limited the evaluation of this system's performance — despite Demak Regency, as the downstream area, having recorded 89 flood events between 1998 and 2023, with a peak flood discharge in 2024 reaching 1,682.9 m³/s. This study aims to obtain the characteristics of flood flow and determine the performance of the SELUNA System in controlling the 100-year return period design flood discharge using HEC-ResSim software with the Muskingum flood routing method. Simulations were carried out under two scenarios — Scenario A without flood routing and Scenario B with Muskingum flood routing — across twelve river reaches over a 52-hour simulation period. The <!--[if gte msEquation 12]>K<![endif]--><!--[if !msEquation]--> <!--[endif]--> and <!--[if gte msEquation 12]>X<![endif]--><!--[if !msEquation]--> <!--[endif]--> parameters were determined based on reach length, flow velocity, and river morphology, yielding three classes of <!--[if gte msEquation 12]>X<![endif]--><!--[if !msEquation]--> <!--[endif]--> values (0.20, 0.18, and 0.15) representing the upstream–reservoir connector reaches, the semi-meandering alluvial reaches, and the downstream–coastal river reaches. The simulation results show a peak discharge reduction ranging from 0–78.85% and a peak time delay of 0–39 hours, with the average reduction increasing from 4.87% in the = 0.20 group to 43.52% in the = 0.15 group, confirming that the smaller the <!--[if gte msEquation 12]>X<![endif]--><!--[if !msEquation]--> <!--[endif]--> value, the greater the role of river storage attenuation. However, the 52-hour simulation period was not sufficient to fully capture the peak discharge at several downstream reaches, as the cumulative Muskingum travel time exceeded 36 hours, making the reduction values at those reaches partial in nature. This study confirms that Muskingum flood routing makes a tangible contribution to the performance of the SELUNA System, particularly in providing additional response time for early warning efforts in downstream areas.

Kata Kunci : Sistem SELUNA, penelusuran banjir, metode Muskingum, HEC-ResSim, debit puncak