1. Knowledge of natural hazards

In the field of natural hazards, everyone has witnessed, directly or indirectly, events of a catastrophic nature, or which simply cause damage (floods, landslides, rockfalls). The problem is how to deal with them, to protect people's safety or mitigate the damaging effects of such events. Faced with a situation that is perceived to be globally at risk, three main questions come to mind:

• How do you identify all possible and realistic scenarios?

• How can we characterize the intensity parameters of each of these scenarios?

• For each of them, how do you specify a timeframe for occurrence?

These questions are fundamental, but highly complex. And yet, the answers are eagerly awaited, enabling us to define appropriate prevention methods and techniques, as well as any necessary contingency plans....