The climate and topography characteristics of Tuy Hoa city, Phu Yen province are quite complicated and being affected by most types of natural disasters, in which storms and floods frequently occur in the downstream of rivers. Huge amount of water from upstream in combination with local downpour have caused numerous flash floods. Rach Bau Ha, the main flood-discharge of the city, is a low-lying area and often being submerged during rainstorms. This article aims to apply MIKE model in forecasting the flood discharge and storage capacity of Rach Bau Ha response to climate change scenarios and proposing appropriate alternatives for the purpose of minimizing flood in the research area. Collected hydro-meteorological, topographical and geological data, previous research results, synthesis, analysis and calculation of designed hydro-meteorological characteristics will be used as input for the MIKE model. The results show that the cross-sectional area and lake area of Rach Bau Ha according to a scenario (lake surface area F = 12.50 ha) completely ensure the flood discharge and storage of Rach Bau Ha, without much increase of the maximum water level and inundation duration, ensure that the water levels of the canal shall not affect inhabitants and infrastructure of the vicinity