Consideration of flood types in flood statistics

Sub-project 1 of the DFG research unit dealt with the event analysis of extreme floods. For this purpose, about 60,000 flood events at 263 gauges were analysed. It became obvious that although floods have very different courses, they can be divided into five event types with regard to their meteorological causes. This called into question the paradigm of a homogeneous sample of annual maximum values that has existed in flood statistics since the 1940s. As an alternative, a methodology was developed for estimating type-specific distribution functions from partial series and combining them into an overall distribution using a mixture model. The advantages of this new statistical model are that it is now possible to determine the different frequencies of individual event types and their influence on the overall distribution, differentiated according to frequent and infrequent flood peak values, as well as to describe the dependencies between peak, fullness and hydrograph shapes in a type-dependent manner and to use them as new design bases. Further application possibilities result from the derivation of spatial flood scenarios based on probabilistic hydrographs in river basins with probability state -ments and the possibility to record and statistically consider the temporal variability of the frequencies and intensities of the individual types. This paper gives an overview of the most important results for a selection of catchments in Bavaria and the Rhine River.