STUDI PENGENDALIAN BANJIR SUNGAI BENGAWAN SOLO DI KECAMATAN KARANGGENENG DAN KECAMATAN LAREN KABUPATEN LAMONGAN

Flooding in the Bengawan Solo River Basin, particularly in Lamongan Regency, remains a major problem due to the river’s limited capacity to accommodate the design flood discharge. One of the flood control measures that can be implemented is the planning of river diversion channels and levees. This study aims to evaluate and design a diversion channel and river levee system as an effort to reduce flood risk based on comprehensive technical analyses. The methodology includes hydrological analysis to determine the 20-year return period design flood discharge, hydraulic analysis using HEC-RAS 6.7 software to evaluate water surface profiles, and slope stability analysis of earthen levees using GeoSlope software with the Bishop method. The results indicate that at several river stations, water levels exceed the existing riverbanks, necessitating the construction of diversion channels and levees with a planned height of up to 3.83 m, including freeboard. Stability analysis shows that the designed levees are safe against overturning, sliding, and slope failure under both normal and extreme conditions. In addition, a cost estimate analysis was conducted to assess the feasibility of project implementation. The planned diversion channel and levee system are expected to reduce flood potential and enhance safety and protection for areas surrounding the river.