In recent years, Climate Change is commonly known as global warming and associated with sea level rise. Such processes are some one of the most serious challenges facing the human beings in the 21st century. Under the impact of this phenomena, extreme climatic phenomena are supposed to more frequent and serious, leading to natural disasters especially related to water. Flood risk represent a major issue especially for developing countries where the economy as well as the adapted capacity against disaster are still poor. As shown in World Bank studies, with more than 70% of the population works in the agriculture, inhabitants essentially concentrate at the coastal plain, Vietnam is among the countries most heavily affected by the consequences of climate change. To get more understanding the impact of this natural phenomena to Vietnamese people, a methodology has been elaborated in order to asses different climate scenarios over a large catchment and flood dynamic. The simulatiosn are based on a validated deterministic hydrological model which is integrating geology, soil, topography, river systems and climate variables. The validation of the model is obtained through measurements and observationsmade at different stations within the catchement. The actual climate (30 years) is properly reproduced by the model and provide a clear view about the flood processes. Future climate is obtained from downscaled GCM data that provide 30 years of hydrological variables to the 2050 and 2100 horizons. The new simulation allows to analyze the changes in the flood dynamic and to perform the frequency and the return period anlaysis. The approach allows to provide an operational approach for integrating the climate change within the engineering design activitiesdedicated to flood protection measures and resilience strategies.