Sumiadi, V. Dermawan, E. Senjawati
Flooding is among Indonesia's most frequent natural hazards, driven by intense rainfall, land-use change, declining infiltration, and river capacity constraints. The Likupang River (North Minahasa Regency) is highly flood-prone due to flat topography, expanding settlements, and sedimentation that reduces conveyance. This study develops flood-inundation modeling for the Likupang River to support mitigation planning. Design discharges were estimated using the SCS method in HEC-HMS, and hydraulic simulations were performed in HEC-RAS 6.2 to assess existing water-surface profiles and inundation extents. Control options were tested, including channel normalization and retarding basins. Results show design peak flows of 72.8 m3/s (25-year) and 79.1 m3/s (50-year). Under existing conditions, overflow occurs at 17 cross sections, mainly downstream. Inundation reaches 4.74 ha (left bank) and 1.74 ha (right bank), affecting ∼535 residents, with impacts on residential areas, agriculture, and infrastructure. A structural package - channel normalization from RS. 26 to RS. 723 and a downstream retarding basin (202,000 m3) - reduces the Q25 discharge to 57.25 m3/s. Post-mitigation profiles under Q25 and Q50 show no overflow along the river. The modeling produces actionable inundation maps and demonstrates that targeted structural measures can substantially lower flood risk, informing levee placement, river works, early-warning design, and spatial planning in North Minahasa. © 2026 Published under licence by IOP Publishing Ltd.
Water Resources Engineering Department, Faculty of Engineering, Universitas Brawijaya, Malang, Indonesia
