This study presents a flood‑mitigation strategy for the Sutlej River basin, tested on a scaled‑down channel model with dimensions validated through a field survey to obtain accurate channel and floodplain and a proportionally reduced inlet velocity. Staggered rows of passive triangular columns on the floodplain guide flow back into the main channel. A detailed 3D reach model was constructed in ANSYS Workbench and solved in Fluent under three scenarios—flow confined to the channel, overbank flow on the floodplain without structures, and flow on a floodplain fitted with triangular columns—using a fine tetrahedral mesh, a constant velocity inlet of 0.30 m/s, and a pressure‑outlet condition. Quantitative results demonstrate that just two rows of columns reduce downstream peak velocity by 20 % (from 0.30 m/s to 0.24 m/s) and lower specific energy by 36 % (from 0.00459 m to 0.00294 m), confirming effective dissipation of flow energy. Streamline analysis indicates flow convergence toward the channel center as pressure builds upstream of the columns, thereby enhancing central alignment and preventing excessive lateral spread across the floodplain. Observed lateral inundation extent is substantially curtailed compared to the unmodified case, while upstream water levels remain stable with negligible backwater effects. These quantitative benchmarks confirm that passive triangular column arrays outperform conventional overbank measures by redirecting flow momentum into the main channel and preserving hydraulic stability.