From small to extreme floods

• Applicant: Dr. Sergiy Vorogushyn
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278017089

Subproject 3 aims to understand how extreme floods differ from small floods and how they can be extrapolated from small to extreme events. We will explore mechanisms and process interactions, which generate heavy tail behaviour in flood probability distributions. Threshold processes and other mechanisms leading to non-linearity as the flood magnitude changes will be studied in the 2nd phase using modelling approaches encompassing the complete flood process cascade. The patterns of upper tail behaviour detected in the data based approach in the 1st phase will be scrutinized by simulation studies with focus on the underlying processes. The following science questions are addressed in the 2nd phase:• Which mechanisms and process interactions tend to generate heavy tails? What is the specific role of threshold processes for the development of extreme floods?• Are large floods generated by different mechanisms than small floods? How does the degree and source of non-linearity of processes (e.g. heavy rainfall, catchment response, flood wave transformation) change with increasing flood magnitude? This subproject will for the first time systematically analyse heavy tails of flood distributions and the entire spectrum of processes and controls that lead to heavy tail behaviour. The novel approach of identifying the responsible processes using a comprehensive simulation model of the entire process chain is embedded in a rigorous hypothesis testing framework. We expect to identify catchment characteristics, atmospheric, hydrological and hydrodynamic processes, which may produce or preclude heavy tails in flood distributions, and thus contribute to a better predictability of floods.

• DFG Programme: Research Units
• Subproject of: FOR 2416: Space-Time Dynamics of Extreme Floods (SPATE)
• Co-Investigator: Professor Dr. Bruno Merz