Fluvial geomorphology and flood-risk management

This paper focuses on the contribution of fluvial geomorphology to flood management. We define what fluvial geomorphologists understand by “fluvial risk” and examine the relationship between fluvial geomorphology and fluvial hazards. The paper details how fluvial geomorphology can present innovative approaches to flood prevention, river maintainance and floodplain restoration. Management of soil erosion and floodwaters is the key question in the plateaus and plains of northern France. In mountainous terrain, strong connectivity between the slopes and high order streams induces permanent risk for local people living near the river, on alluvial fans or on the lower river terraces as demonstrated in the French Alps and in Nepal Himalayas. Management of debris flows resulting from interaction of erosion processes on the slopes and valley bottom is of fundamental importance. The paper highlights the diversity of concepts and methods, such as hydrogeomorphological mapping, sediment budget and functional flood areas, developed by fluvial geomorphologists in order to understand spatio-temporal variability of flood hazard and induced flood risk in temperate, Mediterranean and mountainous areas. The discussion places the existing research in the context of the main ecological issues, future climate change and the constraints imposed by the land-use conflicts, political and social choices and the need to preserve natural heritage.