This booklet on floods explains the phenomenon, with some definitions, how floods form and the influence of natural factors. It also describes the flood return season, the heighth and duration of submersion, flow velocity and volume of material displaced. It underlines the influence of anthropogenic factors, and the human, material and environmental consequences of floods, illustrated by some phenomena in France. The French Ministry of Ecology and sustainable Development has set up the www.prim.net web site fully dedicated to major risk reduction, which provides statistics by town. Then it reviews prevention and relief measures, as well as victim compensation. (UNEsCO)