Flood types - controls in a changing world

• Applicant: Professor Dr. Ralf Merz
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278017089

The event classification developed during the first funding period enables sorting the plethora of different rainfall-runoff events into typical representatives, with a clear description of similarities and differences in triggering mechanisms and event characteristics. The classification allows us to identify and compare only those events stemming from similar processes, and gives insight into the spatio-temporal changes of differing flood producing factors. In the first phase of the project, causative types of runoff events have been defined from a hydrological perspective by considering patterns of rainfall and snowmelt events within each catchment, coinciding catchment state and routing effects. In the second phase in collaboration with SP 2 we will decipher the links between the occurrence of event types and atmospheric drivers, such as blocking conditions, cyclone tracks, circulation patterns and long-term climatic variability, to understand the causative chain of event type occurrence.To account for expected increasing water holding capacity of the atmosphere and hence increasing importance of extreme rainfall events, we will extend the validity of the event typology developed in PH1 beyond mesoscale catchments by considering space-time dynamics of rainfall events at finer temporal resolution in small catchments. Together with SP 3, we will also account for routing effects in large catchments using a coupled hydrological-hydraulic modeling approach , as possible changes in river routing due to river training are expected to change future flood behavior as well. While the first phase has focused on past changes of event types in space and time, in the second phase we will analyse the drivers of change and we will tackle the question of how the occurrence of event types will possibly change in the future if, e.g., climatic conditions, such as the frequency of rainfall events with high intensities, will change. The analysis of the future evolution of event types will be based on scenarios using the classification scheme developed in the first period driven by modelled inputs provided by SP2.Finally, we will shed light on the ability of state-of-the-art conceptual hydrological models to represent streamflow dynamics of specific event types. This will provide valuable information on the reliability and uncertainty of model-based predictions of future floods.

• DFG Programme: Research Units
• Subproject of: FOR 2416: Space-Time Dynamics of Extreme Floods (SPATE)