Debris flow warning through radar nowcasting and critical rainfall thresholds: a case study in the Glarus catchment (Switzerland)

Abstract

The mitigation of debris flow (DF) risk can be achieved by the means of reliable warning systems. At present time, operational warning systems are mostly based on critical rainfall thresholds (CRT) derived through the elaboration of past event records. The prediction ability of these systems strictly depends on the quality and availability of historical data. In order to overcome these limitations, in this work the CRT curves are derived from mathematical and numerical simulations carried out using a coupled hydrological-stability model. The CRT curves thus obtained are combined with rainfall nowcasts based on the observations of meteorological radar network. A case study in central Switzerland is presented. The performances of the proposed system are tested through a playback analysis of a past event. It results that the use of nowcasting allows for a crucial increment of the advance time interval.