The number of people at risk from floods is projected to rise from 1.2 billion today to around 1.6 billion in 2050 (nearly 20% of the world’s population). The economic value of assets at risk is expected to be around USD 45 trillion by 2050, a growth of over 340% from 2010. However, the appropriate responses will share several features: more attention will be paid to (ecologically sensitive) water storage, investment in water supply and sanitation, pollution control, and allocation issues. These costs are not well known, as information is scarce and patchy.