An integrated impact assessment methodology is developed and applied to estimate current and future economic impacts of flood risk in Italy under climate change. The methodology combines a high resolution spatial analysis with a regionally-calibrated version of a global Computable General Equilibrium (CGE) model. The economic effects are estimated per region, in terms of Gross Regional Product from 1980 till 2100. Climate change effects are based on 12 climate simulations. Losses are estimated for two disaster risk management scenarios: with and without adaptation to changing river discharge conditions. Our results show that in Italy, because of climate change, current aggregated ensemble-based expected annual output losses increase 25 percent by the end of the century with adaptation, and fourfold without adaptation, exceeding 600 million Euro per year. The paper provides the distribution of adaptation benefits across regions, which cumulative value exceed 23 billion Euro over the long term (2014- 2100) and 11 before 2050.