Analisis Hidrodinamika 2D Aliran Di Tikungan Sungai Kali Wates Menggunakan Iber

ADEX LAKSMI DEWI, Prof. Dr. Ir. Bambang Agus Kironoto; Prof. Ir. Adam Pamudji Rahardjo, M.Sc., Ph.D., IPM.

2026 | Tesis | S2 Teknik Sipil

Banjir yang melanda Ruas Sungai Kali Wates, Kabupaten Jember, pada 9 November 2025 menyebabkan erosi tebing pada sisi luar tikungan sungai hingga menimbulkan keruntuhan tebing, kerusakan rumah warga, dan terputusnya akses jalan. Mekanisme penggerusan oleh aliran pada tikungan tersebut belum pernah dikaji secara kuantitatif, sehingga penelitian ini bertujuan mengetahui karakteristik hidrodinamika aliran dan zona potensi erosi relatif pada segmen tikungan menggunakan pemodelan hidrodinamika dua dimensi (2D) berbasis perangkat lunak Iber.

Simulasi dilakukan pada kondisi debit banjir rancangan kala ulang 25 tahun (Q25) dengan geometri yang disusun dari data survei topografi lapangan (Total Station) dan DEMNAS melalui interpolasi Triangulated Irregular Network (TIN). Koefisien kekasaran Manning ditetapkan menggunakan metode Cowan (n = 0.056 sebagai nilai dasar) tanpa kalibrasi langsung akibat keterbatasan data lapangan, dan diuji kepekaannya melalui analisis sensitivitas pada rentang n = 0.045–0.065. Parameter hidrodinamika yang dianalisis meliputi kecepatan, kedalaman, elevasi muka air, bilangan Froude, dan tegangan geser dasar pada tiga penampang tinjauan.

Hasil Penelitian menunjukan bahwa distribusi kecepatan, kedalaman, dan tegangan geser dasar secara konsisten terkonsentrasi pada sisi luar tikungan dengan pola migrasi thalweg mengikuti kelengkungan sungai, sementara aliran tetap berada pada rezim subkritis (Fr < 1>

A flood that struck the Kali Wates River, Jember Regency, on 9 November 2025 caused erosion of the outer bank of a river bend , resulting in a partial bank collapse, damage to a resident's house, and disruption of road access. The flow-induced scouring mechanism at this bend has not previously been quantitatively assessed. This study therefore aims to determine the hydrodynamic characteristics of the flow and the zones of relative erosion potential along the bend segment using two-dimensional (2D) hydrodynamic modeling with the Iber software.

Simulations were conducted for a 25-year return period design flood discharge (Q25), with model geometry constructed from field topographic survey data (Total Station) and DEMNAS national elevation data through Triangulated Irregular Network (TIN) interpolation. Manning's roughness coefficient was determined using the Cowan method (n = 0.056 as the base case) without direct calibration due to limited field data, and its sensitivity was examined over a range of n = 0.045–0.065. The hydrodynamic parameters analyzed, flow velocity, depth, water surface elevation, Froude number, and bed shear stress, were evaluated at three selected cross-sections.

The results show that velocity, depth, and bed shear stress consistently concentrate along the outer bank of the bend, with the thalweg migrating in accordance with the channel curvature, while the flow remained subcritical (Fr < 1>

Kata Kunci : hidrodinamika sungai, erosi tebing, tikungan sungai, model Iber 2D