In the Seine basin, flooding is one of the biggest natural hazards, after drought. The Île-de-France metropolitan area is particularly vulnerable to the risk of flooding. The last major floods occurred in May-June 2016 and January-February 2018, costing €1.4 billion and €150 million to €200 million respectively. According to a recent OECD assessment, a 100-year flood reaching the maximum level of the 1910 flood (8.60 metres at the Austerlitz bridge) would cause direct damage totalling around €30 billion. However, the insufficient consideration of this risk by the population and by local government has resulted in a deficient prevention strategy, notably due to poor coordination. The report published today, drawn up by a joint panel of the Court of Accounts and the Île-de-France Regional Audit Chamber, assesses the state of awareness of the risk linked to a 100-year flood of the Seine river, as well as the objectives set and the financial means deployed to prevent this risk. It also examines the effectiveness and efficiency of action taken to reduce this risk. Finally, it analyses the extent to which the governance and sustainable management strategy for the Seine river have contributed to flood risk prevention in recent years.