A Process-Based Framework to Characterize and Classify Runoff Events: The Event Typology of Germany

This study proposes a new processbased framework to characterize and classify runoff eventsof various magnitudes occurring in a wide range of catchments. The framework uses dimensionlessindicators that characterize space–time dynamics of precipitation events and their spatial interaction withantecedent catchment states, described as snow cover, distribution of frozen soils, and soil moisturecontent. A rigorous uncertainty analysis showed that the developed indicators are robust and regionallyconsistent. Relying on covariance and ratiobased indicators leads to reduced classication uncertaintycompared to commonly used (eventbased) indicators based on absolute values of metrics such as duration,volume, and intensity of precipitation events. The event typology derived from the proposed frameworkis able to stratify events that exhibit distinct hydrograph dynamics even if streamow is not directly used forclassication. The derived typology is therefore able to capture rstorder controls of event runoffresponse in a wide variety of catchments. Application of this typology to about 180,000 runoff eventsobserved in 392 German catchments revealed six distinct regions with homogeneous event type frequencythat match well regions with similar behavior in terms of runoff response identied in Germany. Thedetected seasonal pattern of event type occurrence is regionally consistent and agrees well with theseasonality of hydroclimatic conditions. The proposed framework can be a useful tool for comparativeanalyses of regional differences and similarities of runoff generation processes at catchment scale and theirpossible spatial and temporal evolution