Flood risk is the most important natural disaster in France, in terms of the area at risk (20 000 km²), the number of people concerned (4.5 million) and the potential damages caused. According to Munich Re (Munich Re 2005), the number of climatic disasters, including floods, and the losses incurred from these disasters have dramatically increased worldwide over the last 50 years. This is explained both by a higher concentration of people and assets in flood-plains and a higher probability of extreme events linked both to climate change or to the fact that urbanisation, land use and development in rural areas result in greater rainwater runoff (OECD 2006). Since private insurance often chooses not to insure catastrophic risks, many countries, including France, have set-up a national solidarity scheme providing partial or total compensation to victims. The consequence of rising flood risks is that public expenditures to control floods and to provide coverage of flood damages are increasing rapidly. It is thus urgent to find ways of reducing the costs of flood management and insurance.