Evaluasi Kapasitas Penampang Sungai Bingei Kota Binjai terhadap Debit Banjir Menggunakan HEC-RAS

Abstract

Flooding is a natural disaster that significantly affects human life. Floods can be caused by both natural factors and human activities. This study aims to evaluate the cross-sectional capacity of the Bingei River and to propose appropriate solutions for flood control along its course. To achieve this objective, several analyses were conducted, including average maximum rainfall analysis, flood discharge calculation, and the development of a unit hydrograph. The flood discharge was calculated using the Synthetic Unit Hydrograph (SUH) Nakayasu method to determine peak discharges for various return periods.The cross-sectional capacity of the Bingei River was then analyzed using HEC-RAS 6.0 software to assess its ability to convey the design flood discharges. Based on the Nakayasu method, the calculated flood discharges for return periods of 2, 5, 10, 15, 25, 50, and 100 years are 534.86 m³/s, 663.84 m³/s, 740.42 m³/s, 771.53 m³/s, 836.78 m³/s, 906.66 m³/s, and 974.95 m³/s, respectively. The river’s discharge capacities at Sta 8500, Sta 9000, and Sta 9500 are 537.4 m³/s, 580.96 m³/s, and 455.34 m³/s, with corresponding flow velocities of 5.39 m/s, 5.05 m/s, and 5.75 m/s.The analysis results indicate that the existing river cross-sections are inadequate to accommodate flood discharges for return periods greater than 2 years. Therefore, to enhance the river’s capacity and mitigate flooding in vulnerable areas along the Bingei River, the construction of levees with a height of 4 meters, including a 1-meter freeboard, is recommended.