Flood impacts are assessed by estimating affected population and economic damage. Population affected is estimated from population distribution map established for Colombo at 30 m grid resolution. Potential inundation maps are overlaid on the population distribution map to estimate people at risk at real time. To estimate economic damage, we established two sets of damage functions; one for structural damage and content, and the other for commercial and industrial losses. Complete building footprint of Metro Colombo is used for this estimate. Buildings are grouped to 10 building categories and are covered by 4 depth-damage functions. The industrial and commercial buildings are grouped in to 12 categories and are covered by 3 depth damage functions at present. Potential people at risk and potential economic losses are estimated in real time for forecasted inundation and pumping strategies are selected to minimize losses .