In 1910, Paris was subject to a historic flood that is still remembered, and it’s far from a unique event. In France, the risk of flooding is the number-one natural hazard, affecting one in four people, or 17 million residents. Rising river levels are a natural phenomenon that can lead – depending on their intensity (height, speed), duration and geographical reach – to overflow flooding (where the river breaks its banks), and half of all floods are linked to water runoff.