The Duc My Bridge is situated approximately 8 km downstream from the Ea Krong Rou reservoir, within the Dinh River system in Khanh Hoa province. Over the years, the region has been experienced heavy rainfall and flooding, leading to elevated flood levels and alterations in the hydraulic regime downstream of the reservoir. These changes are particularly exacerbated by the impacts of climate change. The Ea Krong Rou reservoir belongs to the group of small reservoirs. This is also the type with the highest rate in Vietnam and is more prone to accidents in the rainy season than other types, so the downstream areas are also greatly affected. The article sets up the input parameters for the Dinh River flood plain using the modelling tool MIKE-FLOOD, which integrates the 1-D MIKE-11 model with the 2-D MIKE-21 model. The results show six scenarios (SC1; SC 1C, SC 2, SC 2C, SC3, SC 3C) with very different flood inundation mapping in Duc My Bridge area and other locations. In addition, the paper also determines the degree of concordance between calculated and observed data. Notably, the roughness coefficient is adjusted in the study area to ensure reasonable results