Calibration of rainfall thresholds for landslide early warning purposes: Applying the EDuMaP method to the system deployed in Campania region (Italy)

The paper investigates the technical performance of a landslide early warning system operating, at regional scale, in Campania region (Italy). The system is managed by the regional civil protection, it covers an area of about 13.600 km2 divided into eight warning zones, it sets the municipality as the minimum territorial unit for warning purposes and it employs four warning levels. Warnings are activated by rain gauge specific rainfall thresholds defined by means of statistical analyses on historical series of rainfalls. The system performance analysis is conducted applying the EDuMaP method which is based on the computation of a duration matrix reporting the time associated with the occurrence of landslide events in relation to warning events, in their respective classes. The dataset used to this purpose refers to landslides recorded within one warning zone from 2010 to 2013 and rainfall data from three rain gauges belonging to different municipalities. Moreover, the rainfall thresholds associated to one of these rain gauges are calibrated by maximizing the performance indicators derived from a set of duration matrices, each one associated to a warning scenario derived from the original one. Yu et al., 2003; Cheung et al., 2006; Godt et al., 2006; Restrepo et al., 2008; Tiranti & Rabuffetti, 2010; Kirschbaum et al., 2012; Martelloni et al., 2012; Peres & Cancelliere, 2012; Staley et al., 2013; Lagomarsino et al., 2013; Greco et al., 2013; Gariano et al., 2015). In this paper, the “Event, Duration Matrix, Performance (EDuMaP) method” (Calvello & Piciullo, 2015) is applied to the warning system operating in Campania (Italy), to assess: the possible occurrence of multiple landslides in a warning zone; the duration of the warnings in relation to the time of occurrence of the landslides; the level of the issued warning in relation to the landslide spatial density in the warning zone; the relative importance system managers attribute to different types of errors. 2 LAnDSLIDE EARLY WARnInG SYSTEM In ThE CAMPAnIA REGIon, ITALY 2.1 Structure of the system The warning system for rainfall-induced landslides in the Campania region, Italy, is managed by the regional civil protection agency as part of the regional warning system developed to deal with the so-called “hydraulic and hydrogeological risks”, i.e. floods and landslides (D.P.G.R. 299, 2005). The Campania region, which has an area