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Timescale: Oct.2015 – Sept.2018
Prof. Dr. Bruno Merz, Helmholtz Centre Potsdam GFZ German Research Centre For Geosciences
Dr. Norbert Marwan, Potsdam Institute for Climate Impact Research PIK
Temporal changes in flood hazard are difficult to detect and attribute, since flood changes are caused by multiple drivers. These drivers, such as human-induced climate change, natural climate variability, implementation of flood defence, river training, or land use change, act on different space-time scales and may mask each other. Recurrence analysis is a modern and powerful method to investigate dynamics, transitions, and even indirect couplings. Further developments of this technique will allow studying data of extreme events, data with uncertainties, and spatio-temporal recurrences.
Objectives and Methods
The PhD-project aims at better understanding and quantifying temporal changes in flood characteristics. Recurrence analysis, a novel and powerful method to investigate dynamics, transitions, and even indirect couplings, will be applied to address the dynamics of flood events at two time scales: At the flood event time scale to understand the interactions of variables that lead to floods, and at the interannual to decadal time scale to understand the dominant controls on the long-term temporal changes in flood hazard. The project is based on a regional, data-driven approach by analysing the recurrence behaviour of several hundred catchments. The flood behaviour of single catchments may be strongly ‘contaminated’ by local effects, such as implementation of flood retention basins. Analysing the regional recurrence behaviour, i.e. the behaviour of many catchments for the same time period, promises to improve the signal-to-noise ratio and to better identify regional drivers of changes.
Transitions are related to a change in the recurrence behaviour of internal dynamics. Recurrence based analysis techniques will be developed and applied to study such changes and to characterise typical transition pathways and potential precursors in the occurrence of floods. We analyse regional-scale changes in flood hazard by adopting recurrence analysis for past flood behaviour of several 100 catchments in Germany, Austria and Switzerland. Probabilistic and spatio-temporal extensions of recurrence analysis will be developed for the characterisation of dynamical transitions, to find potential precursors, and to evaluate uncertainties of the recurrence characteristics.
The spatio-temporal extension of the recurrence approach will also assist other projects using spatio-temporal data, e.g., remote sensing or seismic, within NatRiskChange.
Dadiyorto Wendi is based at the research team “Hydrology” of GFZ.