<p>Floods frequently threaten settlements near river floodplains, leading to significant loss of life and property. Flood modeling is an essential tool for understanding and managing the risks associated with flooding. Reducing the inundation area within the floodplain is critical for effective flood management, serving as a key indicator of flood mitigation success. In this study, channel modifications are examined as a primary approach to reducing floodplain inundation. The impact of these modifications on flood mitigation was simulated using HEC-RAS (Hydrologic Engineering Centre–River Analysis System) version 6.1.0 software. A 15&#xa0;km stretch of the Rapti River, a tributary of the Ghaghara River, and its floodplain were selected as the study area. The model was run under various scenarios, incorporating different flow rates and modified channel geometries, including a modified channel and a cutoff channel. For each scenario, flood inundation area, water depth, and flow velocity within the two-dimensional (2D) flow area were analyzed. The results showed a substantial reduction in floodplain inundation area, water depth, and velocity in modified channels compared to the original channel. Specifically, there was a 46% reduction in inundation area for the modified channel and a 49% reduction for the cutoff channel, relative to the original unmodified channel. These findings indicate that this approach could be an effective flood mitigation measure for similar flood-prone areas.</p>