The recurrence of decadal periods of enhanced/reduced floods in many regions in the world has gained increasing interest of the hydrologic research community. The natural oscillatory behaviour overlaps with human interventions in river morphology and land use changes. In parallel, continuous changes in exposure and susceptibility further shape flood risk. While changes in flood hazard and risk are becoming more often studied, it remains unclear why these changes occur, i.e., what the causes of these changes are. The scope of this session is to report when, where, how (detection) and, more importantly, why (attribution) changes in flood hazard and risk occur; particularly what drivers are responsible for that. Presentations on the impact of climate variability and change, land use changes, morphologic changes in streams, as well as on the role of pre-flood catchment conditions in shaping flood hazard and risk are welcome. Furthermore, contributions on the impact of socio-economic and structural factors on past and future risk changes are invited. This session is jointly organised by the Panta Rhei Working Groups “Understanding Flood Changes” and “Changes in Flood Risk” and will further stimulate scientific discussion on flood change detection and attribution. Specifically, the following topics are of interest for this session:

- Decadal oscillations in rainfall and floods

- Process-informed extreme value statistics

- Detection and attribution of flood hazard changes: climatic drivers, land use controls and river training, among others

- Changes in flood risk: urbanisation of flood prone areas, implementation of risk mitigation measures, changes of economic, societal and technological drivers

- Future flood risk changes and adaptation strategies.

Invited speaker: Jamie Hannaford (Centre for Ecology & Hydrology, UK)