Space–time organization of debris flows-triggering rainfall and its effect on the identification of the rainfall threshold relationship

•Space–time rainfall organization at and around debris flow locations is examined.•Rainfall exhibits a local peak at or around the debris flow locations.•Rainfall spatial decay depends on the duration of the rainfall event.•These space–time features explain the bias in the identified rainfall thresholds. Debris flow occurrence is generally forecasted by means of empirical rainfall depth–duration thresholds based on raingauge observations. Rainfall estimation errors related to the sparse nature of raingauge data are enhanced in case of convective rainfall events characterized by limited spatial extent. Such errors have been shown to cause underestimation of the rainfall thresholds and, thus, less efficient forecasts of debris flows occurrence. This work examines the spatial organization of debris flows-triggering rainfall around the debris flow initiation points using high-resolution, carefully corrected radar data for a set of short duration (