Runoff Discharge and Sedimentation Yield Assessment for Mine Drainage Design in Lateritic Nickel Mining

Abstract

Laterite nickel mining using the open-pit method removes vegetation cover and exposes loose limonite materials, thereby increasing surface runoff and accelerating erosion and sedimentation. Without a quantitatively designed mine drainage system, these conditions may disrupt mining operations and reduce the quality of receiving water bodies. This study aimed to analyze runoff discharge, erosion rate, and sedimentation potential within a nickel mining area in Langgikima District, North Konawe Regency, Southeast Sulawesi, and to utilize the results as the basis for designing open channels and settling ponds. Twenty-one years of rainfall data (2005-2025) were analyzed to determine design rainfall and intensity using the Gumbel distribution and Mononobe equation. Runoff discharge, erosion, and sedimentation potential were estimated using the Rational Method, USLE, and SDR, respectively, and subsequently used to design mine drainage channels and settling ponds based on Manning's equation and Stokes' Law. The design rainfall was 187.26 mm with an intensity of 25.76 mm/h, classified as very heavy—six catchment areas ranging from 0.39 to 1.91 km² produced runoff discharges of 2.25 to 7.67 m³/s. Erosion rates were only 0.08 ton/ha/year in vegetated areas but increased to 66.47- 140.30 ton/ha/year in barren areas, with a total sedimentation potential of 4,012.7 m³/year. The combined channel carrying 13.288 m³/s requires a flow depth of 2.037 m and a bottom width of 2.353 m, whereas the settling pond requires an area of 1,247.7 m² and a storage volume of 6,238.3 m³, achieving a sediment removal efficiency of 91.23%.