ABSTRACT. – Hydrological Hazards. The study contains two separate parts. The first one, entitled “Conceptual Meaning”, analyses problems connected to: the components of the concept of risk, the functional complexity, the classification, the duality, the prediction and the perception of risks, as well as the response after the major hydrological disasters. The second part of the study, entitled “Hydrological Risks”, treats several aspects connected to the classification of risks, the prediction and the diminishment of the hydrological risks, the prevention and the fight against floods, the risk maps and their importance in the territorial management of the hydrological risks.