Exploring Controls on Rainfall‐Runoff Events: 2. Regional Patterns and Spatial Controls of Event Characteristics in Germany

Abstract

AbstractThis study unveils regional patterns of rainfall‐runoff event characteristics in Germany and identifies their spatial controls. Characteristics describing mean value, variability, and seasonality of event runoff coefficient, time scale, rise time, and of the occurrence of multiple‐peak events are derived for a set of 196,073 rainfall‐runoff events observed in 401 mesoscale German catchments. Multiobjective performances of various variable selection methods are used to identify hydrologically relevant variables from a comprehensive set of 115 descriptors of climate, topography, geomorphology, soil, land use, hydrogeology, and geology for every catchment. Results show that although event characteristics have relatively clear regional patterns due to the dominance of climatic controls at regional scale, subsurface properties (i.e., catchment storage) play a considerable role for the prediction of event runoff response. Compared to other tested variable selection methods, the application of a backward elimination procedure allows for the most accurate prediction of spatial patterns and regionalized values of event characteristics identifying soil depth, hydraulic permeability and frequency, size, and seasonality of wet spells as hydrologically relevant catchment descriptors. Climatic and hydrogeological descriptors outperform other generic groups of catchment descriptors. The hydrological interpretation of the emergent regional pattern of event characteristics, their variability, and seasonality provides insight on archetypical catchment behaviors and their controls.