Perancangan Sabodam Untuk Pengendalian Aliran Debris di Batang Jambuah, Agam, Sumatra Barat Berdasarkan SNI 2851:2021

Justin Marinus Oropa, Ir. Karlina, S.T., M.Eng., Ph.D., IPM.

2026 | Skripsi | TEKNIK SIPIL

Batang Jambuah di Kabupaten Agam, Sumatra Barat merupakan salah satu sungai yang berhulu di Gunung Marapi dan berpotensi menyalurkan aliran debris berupa material vulkanik, batuan, dan material organik. Potensi aliran debris pada sungai ini dapat menimbulkan kerugian bagi wilayah hilir sehingga diperlukan bangunan pengendali sebagai upaya mitigasi melalui perancangan sabodam.

Perancangan ini bertujuan merencanakan sabodam sebagai bangunan pengendali aliran debris di Batang Jambuah berdasarkan SNI 2851:2021. Tahapan perancangan meliputi analisis debit banjir rancangan kala ulang 100 tahun menggunakan hidrograf satuan sintetis Nakayasu dan GAMA I, penentuan debit puncak aliran debris, analisis karakteristik sedimen, perancangan dimensi sabodam, serta analisis volume tampungan dan stabilitas bangunan.

Hasil analisis menunjukkan bahwa debit banjir rancangan maksimum diperoleh dengan metode hidrograf satuan sintetis Nakayasu sebesar 155 m³/s, sedangkan debit puncak aliran debris sebesar 310 m³/s. Karakteristik sedimen di Batang Jambuah ditunjukkan oleh diameter butiran rerata (d50) sebesar 8,57 mm yang termasuk kategori kerikil, diameter karakteristik (d95) sebesar 64 mm yang termasuk kategori butiran kasar, dan konsentrasi sedimen sebesar 30%, sehingga aliran pada lokasi studi berpotensi membentuk aliran debris dengan kandungan material padat yang tinggi. Berdasarkan hasil perancangan, diperoleh dimensi sabodam berupa tinggi maindam 6 m dengan kedalaman fondasi 3 m, panjang apron 30 m dengan tebal 1,5 m, tinggi subdam 2,5 m dengan kedalaman fondasi 1,5 m, tinggi pelimpah 3,8 m, lebar pelimpah 3 m, serta slit berukuran 2 m × 3 m sebanyak 3 buah. Bangunan sabodam memenuhi persyaratan stabilitas terhadap guling, geser, dan daya dukung tanah, serta memiliki volume tampungan sedimen sebesar 9244,8 m³ yang terdiri atas volume tampungan mati sebesar 5788,8 m³ dan volume tampungan kontrol sebesar 3456 m³.

Batang Jambuah in Agam Regency, West Sumatra, is one of the rivers originating from Mount Marapi and has the potential to convey debris flow in the form of volcanic material, rock fragments, and organic matter. The potential of debris flow in this river may cause damage to downstream areas, so a control structure is needed as a mitigation measure through the design of a sabodam.

This study aims to design a sabodam as a debris flow control structure in Batang Jambuah based on SNI 2851:2021. The design stages include the analysis of the 100 year design flood using the Nakayasu and GAMA I synthetic unit hydrograph methods, the determination of peak debris flow discharge, sediment characteristic analysis, sabodam dimension design, and the analysis of storage capacity and structural stability.

The results show that the maximum design flood discharge was obtained using the Nakayasu synthetic unit hydrograph method at 155 m³/s, while the peak debris flow discharge was 310 m³/s. Sediment characteristics in Batang Jambuah are indicated by a median grain diameter d50 of 8.57 mm, which is classified as gravel, a characteristic diameter d95 of 64 mm, which is classified as coarse particles, and a sediment concentration of 30%, indicating that the flow at the study site has a high solid material content and the potential to develop into debris flow. Based on the design results, the sabodam dimensions consist of a main dam height of 6 m with a foundation depth of 3 m, an apron length of 30 m with a thickness of 1.5 m, a subdam height of 2.5 m with a foundation depth of 1.5 m, a spillway height of 3.8 m, a spillway width of 3 m, and three slits measuring 2 m × 3 m each. The designed sabodam satisfies the stability requirements against overturning, sliding, and bearing capacity failure, and has a sediment storage capacity of 9,244.8 m³, consisting of a dead storage volume of 5,788.8 m³ and a control storage volume of 3,456 m³.

Kata Kunci : Sabodam, aliran debris, sedimen vulkanik, mitigasi bencana, bangunan pengendali sedimen.