The study focused on flooding along the Gumara River, and the resulting damages such as property destruction, agricultural losses, and displacement of people. Data on rainfall, stream flow, and spatial information were collected, including Digital Elevation Models, land use/land cover maps, and soil maps. Missing rainfall data were addressed using information from meteorological stations, and data quality was evaluated. Flood frequency analysis was conducted, and the accuracy of the analysis was assessed. The study aimed to map flood inundation and analyzes of impacts of the constructing a dyke using the HEC-RAS models. The HEC-HMS model performed well, providing estimates of peak discharge for different return periods. The HEC-RAS model was used to analyze flood extents before and after dyke construction. The construction of the dyke resulted in a reduction in flooded areas for each return periods, with varying percentages of flood impact reduction. However, it is important to note that the dyke did not completely prevent the impact of flooding. The study area remains highly vulnerable, particularly during the summer season from July to August. Therefore, the study recommends the construction of a storage dam upstream of the Gumara Bridge for flood routing services to protect downstream communities. Additionally, implementing a silt excluder and river channelization would be more beneficial than constructing a dyke. Furthermore, constructing dykes and other structures along the Gumara River tributaries could further help mitigate flooding in the region. KEYWORDS: - HEC RAS, GIS, Gumara River,HEC-HMS