The system of water management in Romania has undergone various stages of evolution associated with government changes and the various floods the country had known. The flood risk is the more appropriate topic for a transdisciplinary analysis since risk understanding has to go through the analysis of the past and future hazard, the territory and the society. The aim of this thesis is to understand and quantify the impact of water management strategies on flood and fluvial system in Romania from the communism period until the integration of the country in European Union, trough the study case of the Lower Siret River. The diachronic analysis of interactions between social system and fluvial system is based on the study of hydro-climatic data, of various map material integrated into a GIS and of legislation and engineering texts. The results show that the past management left traces both on actual water management (development of structural measures and non-questioning the dykes network) and on the river morphology (narrowing of the active band, acceleration of flow velocity and disconnection of the flood plain). The entry of a risk analysis by the event and the geographical approach help to understand the complexity in time and space of interactions and feedbacks between fluvial system and social system.
