|In this study we assess the impact of upstream inundation on the downstream flood risk reduction. The study is conducted for the Davao River in the Philippines, where the basin is prone to flooding and inundation occurs almost every year. In order to achieve the objective, firstly we conduct General Circulation Modeling (GCM) to obtain future climate precipitations. Dynamic downscaling and bias correction are then applied to the GCM model results. These future precipitations are then fed to Rainfall-Runoff-Inundation (RRI) model, which simulates hydrological processes and inundation, to carry out flood hazard assessments for the variety of climate scenarios. Model results suggest that when an extreme event occurs, upper reach of the river, where the river shows a meandering feature and population density is very low, is severely inundated. The inundation results in reducing discharge delivered downstream, which in turn leads to flood risk reduction in the downstream region, where Davao City, the third largest city in the country, is located. In order to evaluate the effect of the upstream inundation in a quantitative fashion, construct levee along the channel to prevent inundation in the upstream inundated area, then the model was run with the same set of input. The result shows that due to increased discharge delivered downstream, inundation in the downstream was significantly severer. It is implied that by utilizing the upstream inundation prone area as a flood retention area, the damage in the downstream can significantly be mitigated.